san
small molecule modulation of splicing factor expression is associated with rescue from cellular senescence
eva latorre et al. 2017
doi.org/10.1186/s12860-017-0147-7
eradication of spontaneous malignancy by local immunotherapy
idit sagiv-barfi et al. 2018
doi.org/10.1126/scitranslmed.aan4488
a single-dose plasmid-launched live-attenuated zika vaccine induces protective immunity
jing zou et al. 2018
doi.org/10.1016/j.ebiom.2018.08.056
water
harps enable water harvesting under light fog conditions
weiwei shi et al. 2020
doi.org/10.1002/adsu.202000040
the fog harp is a great example of a relatively simple, low-tech invention that leverages insight from nature to help communities meet their most basic needs."
The "harp" design uses parallel wires to collect ambient water from fog, whereas current technology in use around the globe relies primarily on a screen mesh. The lab-proven theory for the new device was that parallel wires are more efficient at gathering water, avoiding clogs and enhancing drainage into the collector. The researchers' small-scale early tests showed that in high-fog conditions, their harps outpaced those with meshes by a factor of two to one.
Testing then literally moved to the field. In the open fields of Virginia Tech's Kentland Farm, then-undergraduate Brandon Hart built roofed structures to prevent rainfall from impacting findings. Under these coverings, fog harps were placed side-by-side with three different mesh harvesters: one with wire diameters equivalent to the harp, one with a wire size more optimal to harvesting, and one using Raschel mesh -- a mesh made of flat-panel ribbons in v-shaped arrays between horizontal supports. This v-shaped mesh is currently the most popular among fog harvesting sites around the world.
Whereas heavy fog conditions were used in the lab, the actual fog conditions surrounding Virginia Tech are generally much lighter. As field tests began, Boreyko and Kennedy were skeptical that the available fog would provide the feedback they needed to do adequate testing. They were pleasantly surprised.
As fog began rolling over the hills of the New River Valley, the fog harps always showed results. In thin fog, the collection pipes of the mesh collectors were completely devoid of drips. Even as fog density increased, the harps continued outperforming their companions. Depending on the density of the fog, this ranged from twice as much output to almost 20 times.
Bringing together lab studies and field data, researchers determined that collection potential is the result of multiple factors. Greatest among these is the size of collectable water droplets between mesh and harp. To be harvested in both cases, water must be caught on the mesh or harp as air passes through, traveling downward into collection points by gravity. Fog harps use only vertical wires, creating an unimpeded path for mobile drops. Mesh collectors, by contrast, have both horizontal and vertical construction, and water droplets must be significantly larger to cross the horizontal pieces. In field tests, mesh collectors routinely required droplets reaching a size roughly 100 times larger than those on harps before descending. Water that never drops will simply evaporate and cannot be collected.
"We already knew that in heavy fog, we can get at least two times as much water," said Boreyko. "But realizing in our field tests that we can get up to 20 times more water on average in a moderate fog gives us hope we can dramatically enhance the breadth of regions where fog harvesting is a viable tool for getting decentralized, fresh water."
abstract Fog harvesting is useful for passively collecting fresh water in arid regions, but the efficiency of current mesh‐based harvesters is compromised by their poor drainage. Inspired by the linear needles of redwood trees, “fog harps” are developed whose array of vertical wires enables an unobstructed drainage pathway. A full‐scale (1 m2 frame) fog harp is fabricated by winding a stainless steel wire around a spinning aluminum frame featuring threaded rods. The fog harp is field tested for a full year at a local farm (Blacksburg, VA, USA), alongside the control case of a mesh harvester. Under moderate fog conditions, the fog harp collects anywhere from 2 to 78 times more water compared to the mesh harvesters. Under light fog conditions, the fog harp collects up to several hundred milliliters of water per day while the mesh is unable to collect any water at all. The water harvesting performance of fog harps is therefore unprecedented in two ways: they substantively elevate the performance ceiling when exposed to healthy fog while also enabling, for the first time, appreciable water harvesting under light fog.
membrane-less and non-evaporative desalination of hypersaline brines by temperature swing solvent extraction
chanhee boo et al. 2019
doi.org/10.1021/acs.estlett.9b00182
"temperature swing solvent extraction (TSSE)" -- for hypersaline brines. The study, published online in Environmental Science & Technology Letters, demonstrates that TSSE can desalinate very high-salinity brines, up to seven times the concentration of seawater. This is a good deal more than reverse osmosis, the gold-standard for seawater desalination, and can hold handle approximately twice seawater salt concentrations.
VIDEO: https://youtu.be/P8VPVdZm0r8
Currently, hypersaline brines are desalinated either by membrane (reverse osmosis) or water evaporation (distillation). Each approach has limitations. Reverse osmosis methods are ineffective for high-saline brines because the pressures applied in reverse osmosis scale with the amount of salt: hypersaline brines require prohibitively high pressurizations. Distillation techniques, which evaporate the brine, are very energy-intensive.
Yip has been working on solvent extraction, a separation method widely employed for chemical engineering processes. The relatively inexpensive, simple, and effective separation technique is used in a wide range of industries, including production of fine organic compounds, purification of natural products, and extraction of valuable metal complexes.
"I thought solvent extraction could be a good alternative desalination approach that is radically different from conventional methods because it is membrane-less and not based on evaporative phase-change," Yip says. "Our results show that TSSE could be a disruptive technology -- it's effective, efficient, scalable, and can be sustainably powered."
TSSE utilizes a low-polarity solvent with temperature-dependent water solubility for the selective extraction of water over salt from saline feeds. Because it is membrane-less and not based on evaporation of water, it can sidestep the technical constraints that limit the more traditional methods. Importantly, TSSE is powered by low-grade heat (< 70 C) that is inexpensive and sometimes even free. In the study, TSSE removed up to 98.4% of the salt, which is comparable to reverse osmosis, the gold standard for seawater desalination. The findings also demonstrated high water recovery >50% for the hypersaline brines, also comparable to current seawater desalination operations. But, unlike TSSE, reverse osmosis cannot handle hypersaline brines.
"We think TSSE will be transformational for the water industry," he adds. "It can displace the prevailing practice of costly distillation for desalination of high-salinity brines and tackle higher salinities that RO cannot handle," Yip adds. "This will radically improve the sustainability in the treatment of produced water, inland desalination concentrate, landfill leachate, and other hypersaline streams of emerging importance. We can eliminate the pollution problems from these brines and create cleaner, more useable water for our planet."
Yip's TSSE approach has a clear path to commercialization. The heat input can be sustainably supplied by low-grade thermal sources such as industrial waste heat, shallow-well geothermal, and low-concentration solar collectors. He is now working on further refining how TSSE works as a desalination method so that he can engineer further improvements in performance and test it with real-world samples in the field.
abstract Hypersaline brines are of growing environmental importance but are technologically under-served by today’s desalination methods. Temperature swing solvent extraction (TSSE) is a radically different desalination technology that is membrane-less and not based on evaporative phase change. TSSE utilizes low-temperature heat and a low-polarity solvent with temperature-dependent water solubility for the selective extraction of water over salt from saline feeds. This study demonstrates TSSE desalination of high-salinity brines simulated by NaCl solutions with three amine solvents: diisopropylamine (DIPA), N-ethylcyclohexylamine (ECHA), and N,N-dimethylcyclohexylamine (DMCHA). We show that TSSE can desalinate brines with salinities as high as ≈234000 ppm total dissolved solids (i.e., 4.0 M NaCl) and achieve salt removals up to 98.4%. Among the solvents, DIPA exhibited the highest water extraction efficiency whereas ECHA and DMCHA produced water with the lowest salt content and solvent residue content, respectively. Lastly, a high water recovery of >50% was demonstrated for TSSE desalination of 1.5 M NaCl brine using DIPA in semibatch experiments with multiple extraction cycles. This study underscores the unique capabilities of TSSE for the desalination of hypersaline brines.
green synthesis of low-dimensional aluminum oxide hydroxide and oxide using liquid metal reaction media: ultrahigh flux membranes
ali zavabeti et al. 2018
doi.org/10.1002/adfm.201804057
operation of passive membrane systems for drinking water treatment
p.a. oka, n. khadem, p.r. bérubé 2017
doi.org/10.1016/j.watres.2017.02.065
water harvesting from air with metal-organic frameworks powered by natural sunlight
hyunho kim et al. 2017
doi.org/10.1126/science.aam8743
cold vapor generation beyond the input solar energy limit
haomin song et al. 2018
doi.org/10.1002/advs.201800222
free-standing liquid membranes as unusual particle separators
birgitt boschitsch stogin et al. 2018
doi.org/10.1126/sciadv.aat3276
hydrophilic directional slippery rough surfaces for water harvesting
xianming dai et al. 2018
doi.org/10.1126/sciadv.aaq0919
actinia-like multifunctional nanocoagulant for single-step removal of water contaminants
jinwei liu et al. 2018
doi.org/10.1038/s41565-018-0307-8
subambient cooling of water: toward real-world applications of daytime radiative cooling
dongliang zhao et al. 2018
doi.org/10.1016/j.joule.2018.10.006
•10.6°C subambient cooling of water around noon under direct sunlight
•Subambient cool-water production at various constant temperatures
•The effect of weather conditions on the performance of radiative sky cooling
•kW-scale radiative sky cooling system to demonstrate scalability of the technology
Radiative sky cooling dumps excessive heat to the low-temperature sky through infrared thermal radiation. Recent advances in materials have led to the breakthrough in daytime radiative cooling, with subambient temperatures achieved. In this work, we demonstrate for the first time the cooling of water (with large thermal mass) to 10.6°C below ambient around noon under direct sunlight. The effects of different operating temperatures and weather conditions (local wind speed, precipitable water, and cloud cover) on the performance of radiative sky cooling have been investigated, which are essential for real-world applications. A kW-scale radiative sky cooling system with 13.5 m2 radiative surface area has been built to demonstrate scalability of the technology. As cooling demand increases dramatically in the 21st century, this work paves the way for promoting radiative sky cooling for energy saving, water saving, and more efficient power generation in the near future.
Real-world applications of radiative sky cooling require thoughtful design of the system, along with clear understanding of weather effects on system performance. This work explores application of radiative sky cooling based upon a low-cost radiative cooling metamaterial that can be scalably manufactured. A radiative cooled-cold collection (RadiCold) module is developed to cool water to 10.6°C below ambient at noon under stationary conditions. The effects of different weather conditions (wind speed, precipitable water, and cloud cover) on the performance of radiative cooling have been investigated. A kilowatt (kW)-scale RadiCold system with 13.5 m2 radiative cooling surface area is then built and demonstrated to provide a maximum cooling power of 1,296 W at night, and an average cooling power of 607 W at noon (12–2 p.m.) under 952 W/m2 average solar irradiance at 26.5 L/(h⋅m2) volumetric flow rate. A building-integrated RadiCold system is proposed to provide continuous day-and-night cooling.
contactless steam generation and superheating under one sun illumination
thomas a. cooper et al. 2018
doi.org/10.1038/s41467-018-07494-2
On a sunny day, the structure can passively pump out steam hot enough to sterilize medical equipment, as well as to use in cooking and cleaning. The steam may also supply heat to industrial processes, or it could be collected and condensed to produce desalinated, distilled drinking water.
The researchers previously developed a sponge-like structure that floated in a container of water and turned the water it absorbed into steam. But a big concern is that contaminants in the water caused the structure to degrade over time. The new device is designed to be suspended over the water, to avoid any possible contamination.
The suspended device is about the size and thickness of a small digital tablet or e-reader, and is structured like a sandwich: The top layer is made from a material that efficiently absorbs the sun's heat, while the bottom layer efficiently emits that heat to the water below. Once the water reaches the boiling point (100 C), it releases steam that rises back up into the device, where it is funneled through the middle layer -- a foam-like material that further heats the steam above the boiling point, before it's pumped out through a single tube.
"It's a completely passive system -- you just leave it outside to absorb sunlight," says Thomas Cooper, assistant professor of mechanical engineering at York University, who led the work as a postdoc at MIT. "You could scale this up to something that could be used in remote climates to generate enough drinking water for a family, or sterilize equipment for one operating room."
The team's results are detailed in a paper to be published in Nature Communications. The study includes researchers from the lab of Gang Chen, the Carl Richard Soderberg Professor of Power Engineering at MIT.
A clever combination
In 2014, Chen's group reported the first demonstration of a simple, solar-driven steam generator, in the form of a graphite-covered carbon foam that floats on water. This structure absorbs and localizes the sun's heat to the water's surface (the heat would otherwise penetrate down through the water). Since then, his group and others have looked to improve the efficiency of the design with materials of varying solar-absorbing properties. But almost every device has been designed to float directly on water, and they have all run into the problem of contamination, as their surfaces come into contact with salt and other impurities in water.
The team decided to design a device that instead is suspended above water. The device is structured to absorb short-wavelength solar energy, which in turn heats up the device, causing it to reradiate this heat, in the form of longer-wavelength infrared radiation, to the water below. Interestingly, the researchers note that infrared wavelengths are more readily absorbed by water, versus solar wavelengths, which would simply pass right through.
For the device's top layer, they chose a metal ceramic composite that is a highly efficient solar absorber. They coated the structure's bottom layer with a material that easily and efficiently emits infared heat. Between these two materials, they sandwiched a layer of reticulated carbon foam -- essentially, a sponge-like material studded with winding tunnels and pores, which retains the sun's incoming heat and can further heat up the steam rising back up through the foam. The researchers also attached a small outlet tube to one end of the foam, through which all the steam can exit and be easily collected.
Finally, they placed the device over a basin of water and surrounded the entire setup with a polymer enclosure to prevent heat from escaping.
"It's this clever engineering of different materials and how they're arranged that allows us to achieve reasonably high efficiencies with this noncontact arrangement," Cooper says.
Full steam ahead
The researchers first tested the structure by running experiments in the lab, using a solar simulator that mimics the characteristics of natural sunlight at varying, controlled intensities. They found that the structure was able to heat a small basin of water to the boiling point and produce superheated steam, at 122 C, under conditions that simulated the sunlight produced on a clear, sunny day. When the researchers increased this solar intensity by 1.7 times, they found the device produced even hotter steam, at 144 C.
On Oct. 21, 2017, they tested the device on the roof of MIT's Building 1, under ambient conditions. The day was clear and bright, and to increase the sun's intensity further, the researchers constructed a simple solar concentrator -- a curved mirror that helps to collect and redirect more sunlight onto the device, thus raising the incoming solar flux, similar to the way a magnifying glass can be used to concentrate a sun's beam to heat up a patch of pavement.
With this added shielding, the structure produced steam in excess of 146 C over the course of 3.5 hours. In subsequent experiments, the team was able to produce steam from sea water, without contaminating the surface of the device with salt crystals. In another set of experiments, they were also able to collect and condense the steam in a flask to produce pure, distilled water.
Chen says that, in addition to overcoming the challenges of contamination, the device's design enables steam to be collected at a single point, in a concentrated stream, whereas previous designs produced more dilute spray.
"This design really solves the fouling problem and the steam collection problem," Chen says. "Now we're looking to make this more efficient and improve the system. There are different opportunities, and we're looking at what are the best options to pursue."
abstract Steam generation using solar energy provides the basis for many sustainable desalination, sanitization, and process heating technologies. Recently, interest has arisen for low-cost floating structures that absorb solar radiation and transfer energy to water via thermal conduction, driving evaporation. However, contact between water and the structure leads to fouling and pins the vapour temperature near the boiling point. Here we demonstrate solar-driven evaporation using a structure not in contact with water. The structure absorbs solar radiation and re-radiates infrared photons, which are directly absorbed by the water within a sub-100 μm penetration depth. Due to the physical separation from the water, fouling is entirely avoided. Due to the thermal separation, the structure is no longer pinned at the boiling point, and is used to superheat the generated steam. We generate steam with temperatures up to 133 °C, demonstrating superheated steam in a non-pressurized system under one sun illumination.
designing bioinspired surfaces for water collection from fog
dev gurera, bharat bhushan 2018
doi.org/10.1098/rsta.2018.0269
The cactus, beetle and desert grasses all collect water condensed from nighttime fog, gathering droplets from the air and filtering them to roots or reservoirs, providing enough hydration to survive.
Drops of water collect on wax-free, water-repellant bumps on a beetle's back, then slide toward the beetle's mouth on the flat surface between the bumps. Desert grasses collect water at their tips, then channel the water toward their root systems via channels in each blade. A cactus collects water on its barbed tips before guiding droplets down conical spines to the base of the plant.
Bhushan's team studied each of these living things and realized they could build a similar -- albeit larger -- system to allow humans to pull water from nighttime fog or condensation.
They started studying the ways by which different surfaces might collect water, and which surfaces might be the most efficient. Using 3D printers, they built surfaces with bumps and barbs, then created enclosed, foggy environments using a commercial humidifier to see which system gathered the most water.
They learned that conical shapes gather more water than do cylindrical shapes -- "which made sense, given what we know about the cactus," Bhushan said. The reason that happens, he said, is because of a physics phenomenon called the Laplace pressure gradient. Water gathers at the tip of the cone, then flows down the cone's slope to the bottom, where a reservoir is waiting.
Grooved surfaces moved water more quickly than ungrooved surfaces -- "which seems obvious in retrospect, because of what we know about grass," Bhushan said. In the research team's experiments, grooved surfaces gathered about twice as much water as ungrooved surfaces.
The materials the cones were made out of mattered, too. Hydrophilic surfaces -- those that allowed water to bead up rather than absorbing it -- gathered the most water.
"The beetle's surface material is heterogeneous, with hydrophilic spots surrounded by hydrophobic regions, which allows water to flow more easily to the beetle's mouth," Bhushan explained.
The research team also experimented on a structure that included multiple cones, and learned that more water accumulated when water droplets could coalesce between cones that were one or two millimeters apart. The team is continuing those experiments, Bhushan said.
The work so far has been done on a laboratory-only level, but Bhushan envisions the work scaled up, with structures in the desert that could gather water from fog or condensation. That water, he thinks, could supplement water from public systems or wells, either on a house-by-house basis, or on a community-wide basis.
There is precedent for the idea: In areas around the world, including the Atacama Desert in Chile, large nets capture water from fog and collect it in reservoirs for farmers and others to use. Those nets might not be the most efficient way of harnessing water from the air, Bhushan believes.
"Water supply is a critically important issue, especially for people of the most arid parts of the world," Bhushan said. "By using bio-inspired technologies, we can help address the challenge of providing clean water to people around the globe, in as efficient a way as possible."
abstract A systematic study is presented on various water collectors, bioinspired by desert beetles, desert grass and cacti. Three water collecting mechanisms including heterogeneous wettability, grooved surfaces, and Laplace pressure gradient, were investigated on flat, cylindrical, conical surfaces, and conical array. It is found that higher water repellency in flat surfaces results in higher water collection rate and inclination angle (with respect to the vertical axis) has little effect. Surfaces with heterogeneous wettability have higher water collection rate than surfaces with homogeneous wettability. Both cylindrical and conical surfaces resulted in comparable water collection rate. However, only the cone transported the water droplets to its base. Heterogeneity, higher inclination and grooves increased the water collection rate. A cone has a higher collection rate per unit area than a flat surface with the same wettability. An array of cones has higher collection rate per unit area than a single cone, because droplets in a conical array coalesce, leading to higher frequency of droplets falling. Adding heterogeneity further increases the difference. Based on the findings, scaled-up designs of beetle-, grass- and cactus-inspired surfaces and nets are presented.
ice
low–interfacial toughness materials for effective large-scale de-icing
kevin golovin et al. 2019
doi.org/10.1126/science.aav1266
overcame a major limitation of previous ice-repellent coatings -- while they worked well on small areas, researchers found in field testing that they didn't shed ice on very large surfaces as effectively as they had hoped. That's an issue, since ice tends to cause the biggest problems on the biggest surfaces -- sapping efficiency, jeopardizing safety and necessitating costly removal.
They cleared this hurdle with a "beautiful demonstration of mechanics." Anish Tuteja, an associate professor of materials science and engineering, described how he and his colleagues turned to a property that isn't well-known in icing research.
"For decades, coating research has focused on lowering adhesion strength -- the force per unit area required to tear a sheet of ice from a surface," Tuteja said. "The problem with this strategy is that the larger the sheet of ice, the more force is required. We found that we were bumping up against the limits of low adhesion strength, and our coatings became ineffective once the surface area got large enough."
The new coatings solve the problem by introducing a second strategy: low interfacial toughness, abbreviated LIT. Surfaces with low interfacial toughness encourage cracks to form between ice and the surface. And unlike breaking an ice sheet's surface adhesion, which requires tearing the entire sheet free, a crack only breaks the surface free along its leading edge. Once that crack starts, it can quickly spread across the entire iced surface, regardless of its size.
"Imagine pulling a rug across a floor," said Michael Thouless, the Janine Johnson Weins Professor of Engineering in mechanical engineering. "The larger the rug, the harder it is to move. You are resisted by the strength of the entire interface between the rug and floor. The frictional force is analogous to the interfacial strength.
"But now imagine there's a wrinkle in that rug. It's easy to keep pushing that wrinkle across the rug, regardless of how big the rug is. The resistance to propagating the wrinkle is analogous to the interfacial toughness that resists the propagation of a crack."
Thouless said the concept of interfacial toughness is well known in the field of fracture mechanics, where it underpins products like laminated surfaces and adhesive-based aircraft joints. But until now, it hadn't been applied in ice mitigation. The advance came when Thouless learned of Tuteja's previous work and saw an opportunity.
"Traditionally, fracture mechanics researchers only care about interfacial toughness, and ice mitigation researchers often only care about interfacial strength," Thouless said. "But both parameters are important for understanding adhesion.
"I pointed out to Anish that if he were to test increasing lengths of ice, he would find the failure load would rise while interfacial strength was important, but then plateau once toughness became important. Anish and his students tried the experiments and ended up with a really beautiful demonstration of the mechanics, and a new concept for ice adhesion."
To test the idea, Tuteja's team used a technique he honed during previous coating research. By mapping out the properties of a vast library of substances and adding interfacial toughness as well as adhesion strength to the equation, they were able to mathematically predict the properties of a coating without the need to physically test each one. This enabled them to concoct a wide variety of combinations, each with a specifically tailored balance between interfacial toughness and adhesion strength.
They tested a variety of coatings on large surfaces -- a rigid aluminum sheet approximately 3 feet square, and a flexible aluminum piece approximately 1 inch wide and 3 feet long, to mimic a power line. On every surface, ice fell off immediately due to its own weight. It stuck fast, however, to the control surfaces, which were identical in size -- one was uncoated and another was coated with an earlier icephobic coating.
The team's next step is to improve its durability of the LIT coatings.
passive antifrosting surfaces using microscopic ice patterns
s. farzad ahmadi et al. 2018
doi.org/10.1021/acsami.8b11285
colossal barocaloric effects near room temperature in plastic crystals of neopentylglycol
p. lloveras et al. 2019
doi.org/10.1038/s41467-019-09730-9
When put under pressure, plastic crystals of neopentylglycol yield huge cooling effects -- enough that they are competitive with conventional coolants. In addition, the material is inexpensive, widely available and functions at close to room temperature. Details are published in the journal Nature Communications.
The gases currently used in the vast majority of refrigerators and air conditioners -- hydrofluorocarbons and hydrocarbons (HFCs and HCs) -- are toxic and flammable. When they leak into the air, they also contribute to global warming.
"Refrigerators and air conditioners based on HFCs and HCs are also relatively inefficient," said Dr Xavier Moya, from the University of Cambridge, who led the research with Professor Josep Lluís Tamarit, from the Universitat Politècnica de Catalunya. "That's important because refrigeration and air conditioning currently devour a fifth of the energy produced worldwide, and demand for cooling is only going up."
To solve these problems, materials scientists around the world have sought alternative solid refrigerants. Moya, a Royal Society Research Fellow in Cambridge's Department of Materials Science and Metallurgy, is one of the leaders in this field.
In their newly published research, Moya and collaborators from the Universitat Politècnica de Catalunya and the Universitat de Barcelona describe the enormous thermal changes under pressure achieved with plastic crystals.
Conventional cooling technologies rely on the thermal changes that occur when a compressed fluid expands. Most cooling devices work by compressing and expanding fluids such as HFCs and HCs. As the fluid expands, it decreases in temperature, cooling its surroundings.
With solids, cooling is achieved by changing the material's microscopic structure. This change can be achieved by applying a magnetic field, an electric field or through mechanic force. For decades, these caloric effects have fallen behind the thermal changes available in fluids, but the discovery of colossal barocaloric effects in a plastic crystal of neopentylglycol (NPG) and other related organic compounds has levelled the playfield.
Due to the nature of their chemical bonds, organic materials are easier to compress, and NPG is widely used in the synthesis of paints, polyesters, plasticisers and lubricants. It's not only widely available but also is inexpensive.
NPG's molecules, composed of carbon, hydrogen and oxygen, are nearly spherical and interact with each other only weakly. These loose bonds in its microscopic structure permit the molecules to rotate relatively freely.
The word "plastic" in "plastic crystals" refers not to its chemical composition but rather to its malleability. Plastic crystals lie at the boundary between solids and liquids.
Compressing NPG yields unprecedentedly large thermal changes due to molecular reconfiguration. The temperature change achieved is comparable with those exploited commercially in HFCs and HCs.
The discovery of colossal barocaloric effects in a plastic crystal should bring barocaloric materials to the forefront of research and development to achieve safe environmentally friendly cooling without compromising performance.
abstract There is currently great interest in replacing the harmful volatile hydrofluorocarbon fluids used in refrigeration and air-conditioning with solid materials that display magnetocaloric, electrocaloric or mechanocaloric effects. However, the field-driven thermal changes in all of these caloric materials fall short with respect to their fluid counterparts. Here we show that plastic crystals of neopentylglycol (CH3)2C(CH2OH)2 display extremely large pressure-driven thermal changes near room temperature due to molecular reconfiguration, that these changes outperform those observed in any type of caloric material, and that these changes are comparable with those exploited commercially in hydrofluorocarbons. Our discovery of colossal barocaloric effects in a plastic crystal should bring barocaloric materials to the forefront of research and development in order to achieve safe environmentally friendly cooling without compromising performance.
frost-free zone on macrotextured surfaces
yuehan yao et al. 2020
doi.org/10.1073/pnas.1915959117
By tweaking the texture of any material’s surface, the team was able to experimentally reduce frost formation by up to 60%. The millimeter-scale surface structure contains an optimized, jagged series of peaks and valleys, which the researchers observed in nature. With this structure, the team also showed theoretically that frost formation could be reduced by up to 80%.
“This idea came from looking at leaves,” said Northwestern’s Kyoo-Chul Park, who led the study. “There is more frost formation on the convex regions of a leaf. On the concave regions (the veins), we see much less frost. We found that it’s the geometry — not the material — that controls this.”
The study will be published today (March 10) in the Proceedings of the National Academy of Sciences. Park is an assistant professor of mechanical engineering in Northwestern’s McCormick School of Engineering.
People who live in cold climates are all-too-familiar with frost. It forms when humid air vapor or condensation make contact with a surface that is below-freezing temperature.
Every winter, people scrape it off their cars or worry about it killing their plants. But frost is more than a nuisance. Frost on airplane wings can create drag, making flight dangerous or even impossible. And, when accumulating inside freezers and refrigerators, frost greatly reduces energy efficiency in appliances.
But frost doesn’t form on everything. For objects, such as leaves, that have rippling geometry, frost forms on the peaks but rarely in the valleys.
“People have noticed this for several thousands of years,” Park said. “Remarkably, there was no explanation for how these patterns form.”
Through experimental work and computational simulations, Park and his collaborators found that condensation is enhanced on the peaks and suppressed in the valleys of wavy surfaces. The small amount of condensed water in the valleys then evaporates, resulting in a frost-free area. Even when Park used a surface material that attracts water, the water still evaporated from the valleys when below the freezing point.
Park used this new information to find the optimal surface texture to prevent frost formation. The winning surface contains millimeter tall peaks and valleys with small (40-60 degree) angles in between.
Although a thin line of frost still forms on the peaks of the surface topography, it can be defrosted with considerably less energy. It also bypasses the need for using liquids with lower frosting points or surface coatings, which can be easily scratched.
“The no-frosting region initiates the defrosting process,” Park said. “So it would reduce the materials and energy used to solve frosting problems. All we have to do is provide others with the guidelines to design these serrated surfaces.”
abstract Numerous studies have focused on designing functional surfaces that delay frost formation or reduce ice adhesion. However, solutions to the scientific challenges of developing antiicing surfaces remain elusive because of degradation such as mechanical wearing. Inspired by the discontinuous frost pattern on natural leaves, here we report findings on the condensation frosting process on surfaces with serrated structures on the millimeter scale, which is distinct from that on a conventional planar surface with microscale/nanoscale textures. Dropwise condensation, during the first stage of frosting, is enhanced on the peaks and suppressed in the valleys, causing frost to initiate from the peaks, regardless of surface chemistry. The condensed droplets in the valley are then evaporated due to the lower vapor pressure of ice compared with water, resulting in a frost-free zone in the valley, which resists frost propagation even on superhydrophilic surfaces. The dependence of the frost-free areal fraction on the geometric parameters and the ambient conditions is elucidated by both numerical simulations based on steady-state diffusion and an analytical method with an understanding of boundary conditions independent of surface chemistry. We envision that this study would provide a unified framework to design surfaces that can spatially control frost formation, crystal growth, diffusion-controlled growth of biominerals, and material deposition over a broad range of applications.
cellular techniques
making stem cells from normal adult human blood
identification of embryonic neural plate border stem cells and their generation by direct reprogramming from adult human blood cells
marc christian thier et al. 2018
doi.org/10.1016/j.stem.2018.11.015
Stem cells are considered to be the all-rounders of our tissues: they can multiply indefinitely and then -- if they are pluripotent embryonic stem cells -- generate all conceivable cell types. In 2006, the Japanese scientist Shinya Yamanaka recognized that such cells could also be produced in the laboratory -- from mature body cells. Four genetic factors alone are sufficient to reverse the course of development and produce so-called induced pluripotent stem cells (iPS) that have identical properties to embryonic stem cells. Yamanaka was awarded the Nobel Prize for Medicine in 2012 for this discovery.
"This was a major breakthrough for stem cell research," said Andreas Trumpp, German Cancer Research Center (DKFZ) and Director of HI-STEM in Heidelberg. "This applies in particular to for research in Germany, where the generation of human embryonic stem cells is not permitted. Stem cells have enormous potential both for basic research and for the development of regenerative therapies that aim to restore diseased tissue in patients. However, reprogramming is also associated with problems: For example, pluripotent cells can form germ line tumors, so-called teratomas.
Another possibility is not to completely turn back the course of development. For the first time, Trumpp's team has succeeded in reprogramming mature human cells in such a way that a defined type of induced neural stem cells is produced that can multiply almost indefinitely. "We used four genetic factors like Yamanaka, but different ones for our reprogramming," explains Marc Christian Thier, first author of the study. "We assumed that our factors would allow reprogramming to an early stage of development of the nervous system."
In the past, other research groups also reprogrammed connective tissue cells into mature nerve cells or neural precursor cells. However, these artificially produced nerve cells often could not be expanded and could therefore hardly be used for therapeutic purposes. "Often, it was a heterogeneous mixture of different cell types that might not exist in the body under physiological conditions," said Andreas Trumpp explaining the problems.
Together with stem cell researcher Frank Edenhofer from the University of Innsbruck and neuroscientist Hannah Monyer from DKFZ and the Heidelberg University Hospital, Trumpp and his team have succeeded in reprogramming different human cells: connective tissue cells of the skin or pancreas as well as peripheral blood cells. "The origin of the cells had no influence on the properties of the stem cells," said Thier. In particular, the possibility of extracting neural stem cells from the blood of patients without invasive intervention is a decisive advantage for future therapeutic approaches.
What is special about the reprogrammed cells of the Heidelberg researchers is that they are a homogeneous cell type that resembles a stage of neural stem cells that occurs during the embryonic development of the nervous system. "Corresponding cells exist in mice and probably also in humans during early embryonic brain development," said Thier. "We have described here a new neural stem cell type in the mammalian embryo.
These so called "induced Neural Plate Border Stem Cells" (iNBSCs) have a broad development potential. The iNBSCs of the Heidelberg scientists are expandable and multipotent and can develop in two different directions. On the one hand, they can take the path of development to mature nerve cells and their supplier cells, the glial cells, i.e. become cells of the central nervous system. On the other hand, they can also develop into cells of the neural crest, from which different cell types emerge, for example peripheral sensitive nerve cells or cartilage and bones of the skull.
The iNBSCs thus form an ideal basis for generating a broad range of different cell types for an individual patient. "These cells have the same genetic material as the donor and are therefore presumably recognized as "self" by the immune system and are not rejected," explains Thier.
The CRISPR/Cas9 gene scissors can be used to modify the iNBSC or repair genetic defects, as the scientists have shown in their experiments. "They are therefore of interesting both for basic research and the search for new active substances and for the development of regenerative therapies, for example in patients with diseases of the nervous system. However until we can use them in patients, a lot of research work will still be necessary," emphasizes Trumpp
abstract •Four factors directly reprogram human somatic cells into self-renewing iNBSCs
•Multipotent iNBSCs can generate CNS and neural crest progeny
•NBSCs can also be obtained by iPSC differentiation or from E8.5 mouse neural folds
•Expandable iNBSCs can be easily modified via CRISPR/Cas9 to model neural diseases
We report the direct reprogramming of both adult human fibroblasts and blood cells into induced neural plate border stem cells (iNBSCs) by ectopic expression of four neural transcription factors. Self-renewing, clonal iNBSCs can be robustly expanded in defined media while retaining multilineage differentiation potential. They generate functional cell types of neural crest and CNS lineages and could be used to model a human pain syndrome via gene editing of SCN9A in iNBSCs. NBSCs can also be derived from human pluripotent stem cells and share functional and molecular features with NBSCs isolated from embryonic day 8.5 (E8.5) mouse neural folds. Single-cell RNA sequencing identified the anterior hindbrain as the origin of mouse NBSCs, with human iNBSCs sharing a similar regional identity. In summary, we identify embryonic NBSCs and report their generation by direct reprogramming in human, which may facilitate insights into neural development and provide a neural stem cell source for applications in regenerative medicine.
annexin-enriched osteoblast-derived vesicles act as an extracellular site of mineral nucleation within developing stem cell cultures
o. g. davies et al. 2017
doi.org/10.1038/s41598-017-13027-6
peptides derived from the tight junction protein, claudin-1, disrupt skin barrier and promote responsiveness to an epicutaneous vaccine
matthew g. brewer et al. 2019
doi.org/10.1016/j.jid.2019.06.145
overcomes a lot of the challenges faced by microneedle patches for vaccine delivery, the main method that's been tested over the years, and our efficacy and lack of toxicity make me excited about the prospect of a product that could have huge implications for global health."
Common skin disease paves the way for needleless flu shot
Transporting big molecules like flu vaccine proteins across the skin is difficult to do, as the skin is intended to keep things out of the body, not to let them in. The study team took lessons learned from the research and treatment of a common inflammatory skin disease to overcome this hurdle and inform their flu vaccine patch strategy.
In patients with eczema, or atopic dermatitis, the skin barrier is leaky, allowing pollens, molds and a host of other allergens to enter through the skin and be sensed by the immune system. Lisa A. Beck, M.D., corresponding author and Dean's Professor of Dermatology at the University of Rochester Medical Center discovered that the expression of a protein called claudin-1 helps maintain barrier strength and lessen the permeability of the skin. Claudin-1 is significantly reduced in eczema patients (hence the leaky skin barrier) compared to individuals without the disease.
In past research, Beck found that decreasing claudin-1 expression in skin cells from healthy donors made the skin more permeable. Beck, Miller, and first author Matthew Brewer, Ph.D., wondered if they could use this induced permeability to get a flu vaccine virus through the skin. The key would be to disrupt the skin barrier long enough to deliver the virus, but not so long to let unwanted things in.
How it works: Dermatology, chemistry and vaccine biology collide
Miller, a chemist, worked with Brewer, who was trained in vaccine biology and immunology, to develop synthetic peptides that bind to and inhibit claudin-1 in an effort to open up the skin barrier. They tested their formulations in human skin cells and identified a peptide that disrupted the barrier without any toxic effects.
Next, they designed a patch containing the synthetic peptide and a recombinant flu vaccine and tested two scenarios. In the first, they placed the patch on mice to prime the immune system and subsequently administrated an intramuscular flu shot to boost immunity. In the second they did the opposite, delivering an intramuscular flu shot first to prime the immune system followed by the patch to boost immunity.
In both scenarios they placed the flu vaccine patch, which looks like a tiny piece of tape, on the backs of mice and left if there for as little as 18 and as long as 36 hours. The patch effectively opened up the skin barrier, as measured by water loss through the skin.
When the patch was placed first there wasn't a significant immune response, suggesting that it might not be effective at taking a flu naïve infant who hasn't received a flu shot or been exposed to the virus to adequate protection. But, it did initiate a robust immune response (as measured by an increase in antibodies to the flu vaccine virus) when it followed the intramuscular shot, suggesting it could boost preexisting immunity for anyone six months or older who has been vaccinated and/or exposed to the virus (mimicking what happens when we get seasonal flu shots year after year).
Importantly, the team saw no physical changes in the skin over the three month period the mice were observed, meaning that the brief barrier disruption didn't increase the risk of infection.
"When we applied the patch with the peptide the mouse skin became permeable for a short time," said Brewer, a postdoctoral fellow in both the Beck and Miller labs. "But as soon as the patch was removed the skin barrier started to close. We saw significant differences as early as one hour after removal, and by 24 hours the skin was back to normal, which is great news from a safety standpoint."
Improved vaccine delivery for global health
Current needle-based vaccines are effective but require medical personnel to deliver, generate biohazards (sharps) requiring disposal, and cause patients pain and anxiety -- all barriers to delivery in developing world countries, which are the areas of greatest need.
"These countries don't have the manpower to vaccinate entire populations," said Beck. "On top of that, there's an aversion to health care in many of these communities. A needle is painful, it's invasive, and that makes things more difficult when you are dealing with a cultural bias against preventative medicine."
A flu vaccine patch could provide a non-invasive way to administer vaccines quickly and cheaply to large numbers of people.
"If you want to vaccinate a village in Africa you don't want to do it with needles," added Miller. "A patch doesn't have to be refrigerated, it can be applied by anyone, and there are no concerns about disposal or needles getting reused."
abstract Keratinocytes express many pattern recognition receptors (PRRs) that enhance the skin’s adaptive immune response to epicutaneous antigens. We have shown that these PRRs are expressed below tight junctions (TJ), strongly implicating TJ disruption as a critical step in antigen responsiveness. To disrupt TJ we designed peptides inspired by the first extracellular loop of the TJ transmembrane protein, claudin-1. These peptides transiently disrupted TJ in the human lung epithelial cell line 16HBE, and delayed TJ formation in primary human keratinocytes. Building on these observations, we tested whether vaccinating mice with an epicutaneous influenza patch containing TJ-disrupting peptides (TJDP) was an effective strategy to elicit an immunogenic response. Application of a TJDP patch resulted in barrier disruption as measured by increased transepithelial water loss. We observed a significant increase in antigen-specific antibodies when we applied patches with TJDP plus antigen (influenza hemagglutinin) in either a patch-prime or a patch-boost model. Collectively, these observations demonstrate that our designed peptides perturb TJ in human lung as well as human and murine skin epithelium enabling epicutaneous vaccine delivery. We anticipate that this approach could obviate currently used needle-based vaccination methods that require administration by health care workers and biohazard waste removal
in situ genetic engineering of tumors for long-lasting and systemic immunotherapy
stephany y. tzeng et al. 2020
doi.org/10.1073/pnas.1916039117
A hallmark of cancer biology is a tumor cell’s ability to essentially hide from the immune system cells whose job is to identify and destroy cancer cells. Current cellular immunotherapies, notably CAR-T, require scientists to chemically alter and enhance a patient’s own harvested immune system T-cells — an expensive and time-consuming process, say the researchers. Other weapons in the arsenal of immunotherapies are drugs, including so-called checkpoint inhibitors, which have broad effects and often lead to unwanted immune-system-associated side effects, including damage to normal tissue.
By contrast, the Johns Hopkins team sought an immune system therapy that can work like a drug but that also individually engineers a tumor and its surrounding environment to draw the immune system cells to it, says Jordan Green, Ph.D.
Green is the director of the biomaterials and drug delivery laboratory and a professor of biomedical engineering at the Johns Hopkins University School of Medicine. “And our process happens entirely within the body,” Green says, “requiring no external manipulation of a patient’s cells.”
To develop the new system, Green and his team, including Stephany Tzeng, Ph.D., a research associate in the Department of Biomedical Engineering at Johns Hopkins, took advantage of a cancer cell’s tendency to internalize molecules from its surroundings. “Cancer cells may be easier to directly genetically manipulate because their DNA has gone haywire, they divide rapidly, and they don’t have the typical checks and balances of normal cells,” says Green.
The team created a polymer-based nanoparticle — a tiny case that slips inside cells. They guided the nanoparticles to cancer cells by injecting them directly into the animals’ tumors.
“The nanoparticle method we developed is widely applicable to many solid tumors despite their variability on an individual and tumor type level,” says Green, also a member of the Johns Hopkins Kimmel Cancer Center.
Once inside the cell, the water-soluble nanoparticle slowly degrades over a day. It contains a ring of DNA, called a plasmid, that does not integrate into the genome and is eventually degraded as the cancer cell divides, but it stays active long enough to alter protein production in the cell.
The additional genomic material from the plasmid makes the tumor cells produce surface proteins called 4-1BBL, which work like red flags to say, “I’m a cancer cell, activate defenses.” The plasmid also forces the cancer cells to secrete chemicals called interleukins into the space around the cells. The 4-1BBL tags and interleukins are like magnets to immune system cells, and they seek to kill the foreign-looking cancer cells.
“Essentially, we’re forcing the tumor to open itself up and instruct immune cells to kill it,” says Tzeng.
In their animal experiments, Tzeng and the Johns Hopkins team injected the loaded nanoparticles into tumors created by implanting mice with either human melanoma or colon cancer cells.
A control group of mice implanted with melanoma cells received systemically an immunotherapy drug known as anti-PD-1 antibody. All of those mice died quickly, within 2.5 to three weeks, due to tumor growth.
Then, the research team injected other groups of mice, which were also injected with the cancer cells, with nanoparticles containing only one or both of the “uncloaking” signals — the genetically encoded 4-1BBL tags and interleukins. In mice with implanted melanomas, the nanoparticles that combined the two signals had a stronger effect than either signal alone. The median, or midpoint, survival of the mice with the combo signal package was 40 days, and about 20% of them lived through the end of the 60-day study period.
The researchers also saw that some of the mice in the treated melanoma group developed vitiligo, a condition in which skin cells lose their pigment. It occurs in humans too, including in people undergoing immunotherapy for melanoma. “It’s generally thought that vitiligo in melanoma patients is a sign that the immunotherapy treatment is working, and the immunotherapy is spreading to other parts of the body where other melanocytes reside,” says Tzeng.
The tumor shrank away in all of the mice with implanted colon tumors that received the nanoparticles with both signals, and they survived through the entire 60-day study period. When the researchers reinjected human colon cancer cells into the sides of mice opposite the original tumors, unlike with age-matched controls, the newly implanted cancer cells failed to form a tumor, suggesting a lasting effect of the boosted immune system.
“The hope is that, eventually, we could develop nanoparticles that hold instructions for a variety of immune-related signals,” says Green, who cautioned that use of the nanoparticle system will remain experimental for years to come. “We are developing this system as an ‘off-the-shelf’ therapy that can induce a personalized systemic anti-tumor response without needing to know the specific genetic makeup of the tumor beforehand.”
abstract Cancer immunotherapy has been the subject of extensive research, but highly effective and broadly applicable methods remain elusive. Moreover, a general approach to engender endogenous patient-specific cellular therapy, without the need for a priori knowledge of tumor antigen, ex vivo cellular manipulation, or cellular manufacture, could dramatically reduce costs and broaden accessibility. Here, we describe a biotechnology based on synthetic, biodegradable nanoparticles that can genetically reprogram cancer cells and their microenvironment in situ so that the cancer cells can act as tumor-associated antigen-presenting cells (tAPCs) by inducing coexpression of a costimulatory molecule (4-1BBL) and immunostimulatory cytokine (IL-12). In B16-F10 melanoma and MC38 colorectal carcinoma mouse models, reprogramming nanoparticles in combination with checkpoint blockade significantly reduced tumor growth over time and, in some cases, cleared the tumor, leading to long-term survivors that were then resistant to the formation of new tumors upon rechallenge at a distant site. In vitro and in vivo analyses confirmed that locally delivered tAPC-reprogramming nanoparticles led to a significant cell-mediated cytotoxic immune response with systemic effects. The systemic tumor-specific and cell-mediated immunotherapy response was achieved without requiring a priori knowledge of tumor-expressed antigens and reflects the translational potential of this nanomedicine.
investigating the physiology of viable but non-culturable bacteria by microfluidics and time-lapse microscopy
rosemary a. bamford et al. 2017
doi.org/10.1186/s12915-017-0465-4
self-sufficient, low-cost microfluidic pumps utilising reinforced balloons
peter thurgood et al. 2019
doi.org/10.1039/c9lc00618d
cost just $2 to make, yet works almost as well as its expensive and cumbersome lab counterparts.
Pumps are used to make biological samples flow through microfluidic devices while their contents are identified beneath a microscope.
This DIY pump came from a collaboration between researchers at RMIT University and the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, who demonstrated its viability in tests to detect aquatic parasites and cancer cells and to study vascular diseases.
Inspired by football
Study lead author and RMIT engineer, Dr Peter Thurgood, said the team took inspiration for the simple invention from footballs, which hold large pressures when reinforced.
"We started with basic latex balloons, then realised that regular stockings made from nylon and elastane could be a perfect match to reinforce them, allowing them to hold significantly higher pressure and function as pumps," Thurgood said.
"By simply wrapping three layers of stockings around the latex balloon we were able to increase its internal pressure by a factor of 10 -- enough to run many water or blood analyses that would usually require large, expensive pumps."
Experiments showed the reinforced balloon pump could be used to operate microfluidic devices for several hours without a significant pressure loss.
The pump also fits easily within an incubator and can be left overnight.
A low-cost field tool where it's needed most
Study co-author and parasitologist at the Walter and Eliza Hall Institute, Associate Professor Aaron Jex, is a leading researcher in global water quality and public health interventions.
He said this simple innovation opened exciting opportunities in field water testing and the ability to test and diagnose patients for infectious pathogens and aquatic micro-organisms at the point-of-care.
"Parasitic micro-organisms have a major impact in impoverished communities in tropical and subtropical regions globally, but also in developed countries including Australia," Jex said.
"In order to address this there is an urgent need for field-based, low-cost diagnostic tools that work in challenging, sometimes remote and often complex environments very different from a pristine laboratory."
"As simple as it may look, this device suits those needs really well and could have a big impact."
Co-author and RMIT biologist, Dr Sara Baratchi, said it also had promising applications for early diagnosis of diseases at home or in the doctor's surgery.
The balloon pump was tested as a point-of-care diagnostic device for detection of very low concentrations of target cancer cells in liquid samples, and found to work.
"The hydrodynamic force of liquid produced by the reinforced balloon was enough to isolate cells for study, which was really amazing for a $2 pump!"
Baratchi is now working on applying the simplified pump technology to develop organ-on-chip systems that mimic the flow conditions in dysfunctional vessels, to better understand diseases like atherosclerosis that lead to heart attack and stroke.
An opportunity for outreach
RMIT engineer and project leader, Dr Khashayar Khoshmanesh, is a leading researcher in the field of microfluidic based lab-on-a-chip technologies.
He said while microfluidics had made significant progress over the past decade, their widespread application had been limited by the cost and bulk of pumps required to operate them.
"Simplicity is at the heart of our entire research program. By redesigning sophisticated microfluidic devices into simplified ones, we can maximise their outreach and applications for use in teaching or research in the field, not just in sophisticated labs," he said.
"We envisage these types of pumps also being suitable for student classwork experiments to support capability development in this important area of research from an earlier stage."
abstract Here, we introduce a simple method for increasing the inflation pressure of self-sufficient pressure pumps made of latex balloons. Our method involves reinforcing the latex balloon with elastane fibres to restrict the expansion of the balloon and increase its inflation pressure. This allowed us to increase the operational inflation pressure of a latex balloon from 2.5 to 25 kPa. Proof-of-concept experiments show the suitability of the reinforced balloon for inducing lateral forces and recirculating flows, which are employed for hydrodynamic capturing of large human monocytes. We also demonstrate the ability for the rapid exchange of solutions in repeated cycles upon manual squeezing of the reinforced balloons. We also show the suitability of the reinforced balloon for studying the mechanobiology of human aortic endothelial cells under various shear stress levels. The simplicity, portability, affordability, hyper-elasticity and scalability of the reinforced balloon pumps make them suitable for a wide range of microfluidic applications.
observing the cell in its native state: imaging subcellular dynamics in multicellular organisms
tsung-li liu et al. 2018
doi.org/10.1126/science.aaq1392
future shock
alvin toffler 1974
the third wave
alvin toffler 1980
ultrasociety: how 10,000 years of war made humans the greatest cooperators on earth
peter turchin 2016 9780996139526
elite cycles of pete turchin
paul rosenberg
Link: salon.com/2015/11/23/this_is_why_were_so_fcked_our_politics_are_only_going_to_get_worse/
if the greatest example of human cooperation is the space station…
criticism of pinker
“ What’s important is not that one’s ideas are correct, but that they are productive.”
secular cycles
peter turchin and sergey a. nefedov 2009
978-0-691-13696-7
ages of discord: a structural-demographic analysis of american history
peter turchin 2016
katy roberts
blame-rich-overeducated-elites-as-society-frays
conservatism and liberalism
paul rosenberg
salon.com
news media literacy and conspiracy theory endorsement
stephanie craft et al. 2017
doi.org/10.1177/2057047317725539
yet another text captcha solver: a generative adversarial network based approach
guixin ye et al. 2018
doi.org/10.1145/3243734.3243754
The new algorithm, based on deep learning methods, is the most effective solver of captcha security and authentication systems to date and is able to defeat versions of text captcha schemes used to defend the majority of the world's most popular websites.
Text-based captchas use a jumble of letters and numbers, along with other security features such as occluding lines, to distinguish between humans and malicious automated computer programmes. It relies on people finding it easier to decipher the characters than machines.
Developed by computer scientists at Lancaster University in the UK as well as Northwest University and Peking University in China, the solver delivers significantly higher accuracy than previous captcha attack systems, and is able to successfully crack versions of captcha where previous attack systems have failed.
The solver is also highly efficient. It can solve a captcha within 0.05 of a second by using a desktop PC.
It works by using a technique known as a 'Generative Adversarial Network', or GAN. This involves teaching a captcha generator programme to produce large numbers of training captchas that are indistinguishable from genuine captchas. These are then used to rapidly train a solver, which is then refined and tested against real captchas.
By using a machine-learned automatic captcha generator the researchers, or would be attackers, are able to significantly reduce the effort, and time, needed to find and manually tag captchas to train their software. It only requires 500 genuine captchas, instead of the millions that would normally be needed to effectively train an attack programme.
Previous captcha solvers are specific to one particular captcha variation. Prior machine-learning attack systems are labour intensive to build, requiring a lot of manual tagging of captchas to train the systems. They are also easily rendered obsolete by small changes in the security features used within captchas.
Because the new solver requires little human involvement it can easily be rebuilt to target new, or modified, captcha schemes.
The programme was tested on 33 captcha schemes, of which 11 are used by many of the world's most popular websites -- including eBay, Wikipedia and Microsoft.
Dr Zheng Wang, Senior Lecturer at Lancaster University's School of Computing and Communications and co-author of the research, said: "This is the first time a GAN-based approach has been used to construct solvers. Our work shows that the security features employed by the current text-based captcha schemes are particularly vulnerable under deep learning methods.
"We show for the first time that an adversary can quickly launch an attack on a new text-based captcha scheme with very low effort. This is scary because it means that this first security defence of many websites is no longer reliable. This means captcha opens up a huge security vulnerability which can be exploited by an attack in many ways.
Mr Guixin Ye, the lead student author of the work said: "It allows an adversary to launch an attack on services, such as Denial of Service attacks or spending spam or fishing messages, to steal personal data or even forge user identities. Given the high success rate of our approach for most of the text captcha schemes, websites should be abandoning captchas."
Researchers believe websites should be considering alternative measures that use multiple layers of security, such as a user's use patterns, the device location or even biometric information.
abstract Despite several attacks have been proposed, text-based CAPTCHAs are still being widely used as a security mechanism. One of the reasons for the pervasive use of text captchas is that many of the prior attacks are scheme-specific and require a labor-intensive and time-consuming process to construct. This means that a change in the captcha security features like a noisier background can simply invalid an earlier attack. This paper presents a generic, yet effective text captcha solver based on the generative adversarial network. Unlike prior machine-learning-based approaches that need a large volume of manually-labeled real captchas to learn an effective solver, our approach requires significantly fewer real captchas but yields much better performance. This is achieved by first learning a captcha synthesizer to automatically generate synthetic captchas to learn a base solver, and then fine-tuning the base solver on a small set of real captchas using transfer learning. We evaluate our approach by applying it to 33 captcha schemes, including 11 schemes that are currently being used by 32 of the top-50 popular websites including Microsoft, Wikipedia, eBay and Google. Our approach is the most capable attack on text captchas seen to date. It outperforms four state-of-the-art text-captcha solvers by not only delivering a significant higher accuracy on all testing schemes, but also successfully attacking schemes where others have zero chance. We show that our approach is highly efficient as it can solve a captcha within 0.05 second using a desktop GPU. We demonstrate that our attack is generally applicable because it can bypass the advanced security features employed by most modern text captcha schemes. We hope the results of our work can encourage the community to revisit the design and practical use of text captchas.
prolegomena to any dark-age psychohistory
venkatesh rao 2017
ribbonfarm
sensing
nilm dashboard: a power system monitor for electromechanical equipment diagnostics
andre aboulian et al. 2019
doi.org/10.1109/tii.2018.2843770
a sensor that simply is attached to the outside of an electrical wire at a single point, without requiring any cutting or splicing of wires. From that single point, it can sense the flow of current in the adjacent wire, and detect the distinctive "signatures" of each motor, pump, or piece of equipment in the circuit by analyzing tiny, unique fluctuations in the voltage and current whenever a device switches on or off. The system can also be used to monitor energy usage, to identify possible efficiency improvements and determine when and where devices are in use or sitting idle.
The technology is especially well-suited for relatively small, contained electrical systems such as those serving a small ship, building, or factory with a limited number of devices to monitor. In a series of tests on a Coast Guard cutter based in Boston, the system provided a dramatic demonstration last year.
About 20 different motors and devices were being tracked by a single dashboard, connected to two different sensors, on the cutter USCGC Spencer. The sensors, which in this case had a hard-wired connection, showed that an anomalous amount of power was being drawn by a component of the ship's main diesel engines called a jacket water heater. At that point, Leeb says, crewmembers were skeptical about the reading but went to check it anyway. The heaters are hidden under protective metal covers, but as soon as the cover was removed from the suspect device, smoke came pouring out, and severe corrosion and broken insulation were clearly revealed.
"The ship is complicated," Leeb says. "It's magnificently run and maintained, but nobody is going to be able to spot everything."
Lt. Col. Nicholas Galanti, engineer officer on the cutter, says "the advance warning from NILM enabled Spencer to procure and replace these heaters during our in-port maintenance period, and deploy with a fully mission-capable jacket water system. Furthermore, NILM detected a serious shock hazard and may have prevented a class Charlie [electrical] fire in our engine room."
The system is designed to be easy to use with little training. The computer dashboard features dials for each device being monitored, with needles that will stay in the green zone when things are normal, but swing into the yellow or red zone when a problem is spotted.
Detecting anomalies before they become serious hazards is the dashboard's primary task, but Leeb points out that it can also perform other useful functions. By constantly monitoring which devices are being used at what times, it could enable energy audits to find devices that were turned on unnecessarily when nobody was using them, or spot less-efficient motors that are drawing more current than their similar counterparts. It could also help ensure that proper maintenance and inspection procedures are being followed, by showing whether or not a device has been activated as scheduled for a given test.
"It's a three-legged stool," Leeb says. The system allows for "energy scorekeeping, activity tracking, and condition-based monitoring." But it's that last capability that could be crucial, "especially for people with mission-critical systems," he says. In addition to the Coast Guard and the Navy, he says, that includes companies such as oil producers or chemical manufacturers, who need to monitor factories and field sites that include flammable and hazardous materials and thus require wide safety margins in their operation.
One important characteristic of the system that is attractive for both military and industrial applications, Leeb says, is that all of its computation and analysis can be done locally, within the system itself, and does not require an internet connection at all, so the system can be physically and electronically isolated and thus highly resistant to any outside tampering or data theft.
Although for testing purposes the team has installed both hard-wired and noncontact versions of the monitoring system -- both types were installed in different parts of the Coast Guard cutter -- the tests have shown that the noncontact version could likely produce sufficient information, making the installation process much simpler. While the anomaly they found on that cutter came from the wired version, Leeb says, "if the noncontact version was installed" in that part of the ship, "we would see almost the same thing."
abstract Nonintrusive load monitoring (NILM) uses electrical measurements taken at a centralized point in a network to monitor many loads downstream. This paper introduces NILM dashboard, a machine intelligence, and graphical platform that uses NILM data for real-time electromechanical system diagnostics. The operation of individual loads is disaggregated using signal processing and presented as time-based load activity and statistical indicators. The software allows multiple NILM devices to be networked together to provide information about loads residing on different electrical branches at the same time. A graphical user interface provides analysis tools for energy scorekeeping, detecting fault conditions, and determining operating state. The NILM dashboard is demonstrated on the power system data from two United States Coast Guard cutters.
ml-dsp: machine learning with digital signal processing for ultrafast, accurate, and scalable genome classification at all taxonomic levels
gurjit s. randhawa et al. 2019
doi.org/10.1186/s12864-019-5571-y
combines supervised machine learning with digital signal processing (ML-DSP), could for the first time make it possible to definitively answer questions such as how many different species exist on Earth and in the oceans. How are existing, newly-discovered, and extinct species related to each other? What are the bacterial origins of human mitochondrial DNA? Do the DNA of a parasite and its host have a similar genomic signature?
The tool also has the potential to positively impact the personalized medicine industry by identifying the specific strain of a virus and thus allowing for precise drugs to be developed and prescribed to treat it.
ML-DSP is an alignment-free software tool which works by transforming a DNA sequence into a digital (numerical) signal, and uses digital signal processing methods to process and distinguish these signals from each other.
"With this method even if we only have small fragments of DNA we can still classify DNA sequences, regardless of their origin, or whether they are natural, synthetic, or computer-generated," said Lila Kari, a professor in Waterloo's Faculty of Mathematics. "Another important potential application of this tool is in the healthcare sector, as in this era of personalized medicine we can classify viruses and customize the treatment of a particular patient depending on the specific strain of the virus that affects them."
In the study, researchers performed a quantitative comparison with other state-of-the-art classification software tools on two small benchmark datasets and one large 4,322 vertebrate mitochondrial genome dataset. "Our results show that ML-DSP overwhelmingly outperforms alignment-based software in terms of processing time, while having classification accuracies that are comparable in the case of small datasets and superior in the case of large datasets," Kari said. "Compared with other alignment-free software, ML-DSP has significantly better classification accuracy and is overall faster."
The authors also conducted preliminary experiments indicating the potential of ML-DSP to be used for other datasets, by classifying 4,271 complete dengue virus genomes into subtypes with 100 per cent accuracy, and 4,710 bacterial genomes into divisions with 95.5 per cent accuracy.
detecting middle ear fluid using smartphones
justin chan et al. 2019
doi.org/10.1126/scitranslmed.aav1102
Ear infections are the most common reason that parents bring their children to a pediatrician, according to the National Institutes of Health.
This condition occurs when fluid builds up in the middle ear behind the eardrum and is infected. This buildup is also common in another condition called otitis media with effusion. Any kind of fluid buildup can be painful and make it hard for children to hear, which can be especially detrimental when they are learning to talk.
Both conditions are hard to diagnose because they have vague symptoms: Sometimes children tug on their ears or have fevers, and sometimes there are no symptoms. In addition, young children may not be able to describe where they hurt.
Now researchers at the University of Washington have created a new smartphone app that can detect fluid behind the eardrum by simply using a piece of paper and a smartphone's microphone and speaker. The smartphone makes a series of soft audible chirps into the ear through a small paper funnel and, depending on the way the chirps are reflected back to the phone, the app determines the likelihood of fluid present with a probability of detection of 85%. This is on par with current methods used by specialists to detect fluid in the middle ear, which involve specialized tools that use acoustics or a puff of air.
The team published its results May 15 in Science Translational Medicine.
"Designing an accurate screening tool on something as ubiquitous as a smartphone can be game changing for parents as well as health care providers in resource limited regions," said co-author Shyam Gollakota, an associate professor in the UW's Paul G. Allen School of Computer Science & Engineering. "A key advantage of our technology is that it does not require any additional hardware other than a piece of paper and a software app running on the smartphone."
Once diagnosed, ear infections can be easily treated with observation or antibiotics, and persistent fluid can be monitored or drained by a doctor to relieve symptoms of pain or hearing loss. A quick screening at home could help parents decide whether or not they need to take their child to the doctor.
This app works by sending sounds into the ear and measuring how those sound waves change as they bounce off the eardrum. The team's system involves a smartphone and a regular piece of paper that the doctor or parent can cut and fold into a funnel. The funnel rests on the outer ear and guides sound waves in and out of the ear canal. When the phone plays a continuous 150 millisecond sound -- which sounds like a bird chirping -- through the funnel, the sound waves bounce off the eardrum, travel back through the funnel and are picked up by the smartphone's microphone along with the original chirps. Depending on whether there's fluid inside, the reflected sound waves interfere with the original chirp sound waves differently.
"It's like tapping a wine glass," said co-first author Justin Chan, a doctoral student in the Allen School. "Depending on how much liquid is in it, you get different sounds. Using machine learning on these sounds, we can detect the presence of liquid."
When there is no fluid behind the eardrum, the eardrum vibrates and sends a variety of sound waves back. These sound waves mildly interfere with the original chirp, creating a broad, shallow dip in the overall signal. But when the eardrum has fluid behind it, it doesn't vibrate as well and reflects the original sound waves back. They interfere more strongly with the original chirp and create a narrow, deep dip in the signal.
To train an algorithm that detects changes in the signal and classifies ears as having fluid or not, the team tested 53 children between the ages of 18 months and 17 years at Seattle Children's Hospital. About half of the children were scheduled to undergo surgery for ear tube placement, a common surgery for patients with chronic or recurrent incidents of ear fluid. The other half were scheduled to undergo a different surgery unrelated to ears, such as a tonsillectomy.
"What is really unique about this study is that we used the gold standard for diagnosing ear infections," said co-first author Dr. Sharat Raju, a surgical resident in otolaryngology-head and neck surgery at the UW School of Medicine. "When we put in ear tubes, we make an incision into the eardrum and drain any fluid present. That's the best way to tell if there is fluid behind the eardrum. So these surgeries created the ideal setting for this study."
After parents provided informed consent, the team recorded the chirps and their resulting sound waves from the patients' ears immediately before surgery. Many of the children responded to the chirps by smiling or laughing.
Among the children getting their ear tubes placed, surgery revealed that 24 ears had fluid behind the eardrum, while 24 ears did not. For children scheduled for other surgeries, two ears had bulging eardrums characteristic of an ear infection, while the other 48 ears were fine. The algorithm correctly identified the likelihood of fluid 85% of the time, which is comparable to current methods that specialized doctors use to diagnose fluid in the inner ear.
Then the team tested the algorithm on 15 ears belonging to younger children between nine and 18 months of age. It correctly classified all five ears that were positive for fluid and nine out of the 10 ears, or 90%, that did not have fluid.
"Even though our algorithm was trained on older kids, it still works well for this age group," said co-author Dr. Randall Bly, an assistant professor of otolaryngology-head and neck surgery at the UW School of Medicine who practices at Seattle Children's Hospital. "This is critical because this group has a high incidence of ear infections."
Because the researchers want parents to be able to use this technology at home, the team trained parents how to use the system on their own children. Parents and doctors folded paper funnels, tested 25 ears and compared the results. Both parents and doctors successfully detected the six fluid-filled ears. Parents and doctors also agreed on 18 out of the 19 ears with no fluid. In addition, the sound wave curves generated by both parent and doctor tests looked similar.
"The ability to know how often and for how long fluid has been present could help us make the best management decisions with patients and parents," Bly said. "It also could help primary care providers know when to refer to a specialist."
The team also tested the algorithm on a variety of smartphones and used different types of paper to make the funnel. The results were consistent regardless of phone or paper type. The researchers plan on commercializing this technology through a spinout company, Edus Health, and then making the app available to the public.
"Fluid behind the eardrum is so common in children that there's a direct need for an accessible and accurate screening tool that can be used at home or clinical settings," Raju said. "If parents could use a piece of hardware they already have to do a quick physical exam that can say 'Your child most likely doesn't have ear fluid' or 'Your child likely has ear fluid, you should make an appointment with your pediatrician,' that would be huge."
abstract The presence of middle ear fluid is a key diagnostic marker for two of the most common pediatric ear diseases: acute otitis media and otitis media with effusion. We present an accessible solution that uses speakers and microphones within existing smartphones to detect middle ear fluid by assessing eardrum mobility. We conducted a clinical study on 98 patient ears at a pediatric surgical center. Using leave-one-out cross-validation to estimate performance on unseen data, we obtained an area under the curve (AUC) of 0.898 for the smartphone-based machine learning algorithm. In comparison, commercial acoustic reflectometry, which requires custom hardware, achieved an AUC of 0.776. Furthermore, we achieved 85% sensitivity and 82% specificity, comparable to published performance measures for tympanometry and pneumatic otoscopy. Similar results were obtained when testing across multiple smartphone platforms. Parents of pediatric patients (n = 25 ears) demonstrated similar performance to trained clinicians when using the smartphone-based system. These results demonstrate the potential for a smartphone to be a low-barrier and effective screening tool for detecting the presence of middle ear fluid.
role of indentation depth and contact area on human perception of softness for haptic interfaces
charles dhong et al. 2019
doi.org/10.1126/sciadv.aaw8845
created equations that can calculate how soft or hard a material will feel based on material thickness, Young's modulus (a measure of a material's stiffness), and micropatterned areas. The equations can also do the reverse and calculate, for example, how thick or micropatterned a material needs to be to feel a certain level of softness.
"What's interesting about this is that we've found two new ways to tune the perceived softness of an object -- micropatterning and changing the thickness," Dhong said. "Young's modulus is what scientists typically turn to in terms of what's soft or hard. It is a factor, but now we show that it's only one part of the equation."
Recreating softness
The researchers began by examining two parameters engineers use to measure a material's perceived softness: indentation depth (how deep a fingertip presses into a material) and contact area between the fingertip and the material. Normally, these parameters both change simultaneously as a fingertip presses into an object. Touch a piece of soft rubber, for example, and the contact area will increase the deeper a fingertip presses in.
Dhong, Lipomi and colleagues were curious how indentation depth and contact area independently affect the perception of softness. To answer this question, they specially engineered materials that decoupled the two parameters and then tested them on human subjects.
The researchers created nine different elastomeric slabs, each with its own unique ratio of indentation depth to contact area. The slabs differed in amount of micropatterning on the surface, thickness and Young's modulus.
Micropatterning is key to the design. It consists of arrays of raised microscopic pillars dotted on the surface of the slabs. These tiny pillars allow a fingertip to press deeper without changing the contact area. This is similar to pressing against the metal pins of a Pinscreen toy, where arrays of pins slide in and out to make a 3D impression.
"By creating these micropatterned surface structures, we produce discontinuous regions of contact where the finger presses in that are much smaller than the shadow it would cast on the surface," Lipomi said.
The team tested the slabs on 15 subjects and instructed them to perform two tasks. In the first task, they presented subjects with multiple pairs of slabs and asked them to identify the softer one in each pair. In the second task, the researchers had subjects rank the nine slabs from softest to hardest.
Overall, the slabs that subjects perceived as softer were thicker, had little to no micropatterning on the surface, and had a low Young's modulus. Meanwhile slabs that felt harder were thinner, had more micropatterning and a high Young's modulus.
Softness: a basic ingredient of touch
Experiments also led the researchers to an interesting conclusion: the perception of softness is a basic sensation, not a combination of other sensations.
"This means softness is a primary ingredient of the human sense of touch. It's like how we have RGB for color displays," Lipomi said. "If we can find the other 'pixels of touch,' can we combine them to make any tactile image we want?
abstract In engineering, the “softness” of an object, as measured by an indenter, manifests as two measurable parameters: (i) indentation depth and (ii) contact area. For humans, softness is not well defined, although it is believed that perception depends on the same two parameters. Decoupling their relative contributions, however, has not been straightforward because most bulk—“off-the-shelf”—materials exhibit the same ratio between the indentation depth and contact area. Here, we decoupled indentation depth and contact area by fabricating elastomeric slabs with precise thicknesses and microstructured surfaces. Human subject experiments using two-alternative forced-choice and magnitude estimation tests showed that the indentation depth and contact area contributed independently to perceived softness. We found an explicit relationship between the perceived softness of an object and its geometric properties. Using this approach, it is possible to design objects for human interaction with a desired level of perceived softness.
a flexible, robust, and gel-free electroencephalogram electrode for noninvasive brain-computer interfaces
sen lin et al. 2019
doi.org/10.1021/acs.nanolett.9b02019
Often used to diagnose seizure disorders and other neurological conditions, EEGs are machines that track and record brain wave patterns. To conduct an EEG, technicians typically use a very sticky gel to attach electrodes to different regions of the patient's scalp. However, this gel is difficult to wash out of hair and sometimes irritates the skin. In addition, hair interferes with the electrical signals. Ming Lei, Bo Hong, Hui Wu and colleagues wanted to develop an EEG electrode that is flexible, robust and gel-free. Such an electrode could help patients, but also might allow people to someday control devices with their brains.
To make the electrodes, the researchers placed silver nanowires in a commercially available melamine sponge. The electrodes cost only about 12 cents each to make and could be mass-produced. The team assembled 10 electrodes into a flexible silicon cap and measured their performance when worn by people with shaved or hairy heads. On hairless skin, the new electrodes recorded brain waves as well as conventional ones. What's more, the flexibility of the electrodes allowed them to perform similarly on hairy and hairless skin, unlike the conventional devices. A volunteer wearing the cap could control a toy car with her mind, making it go forward, backward, left or right. The electrodes are mechanically stable through different cycles and movements and are also resistant to heat and sweat
abstract Brain–computer interfaces (BCIs) enable direct and near-instant communication between the brain and electronic devices. One of the biggest remaining challenges is to develop an effective noninvasive BCI that allows the recording electrodes to avoid hair on human skin without the inconveniences and complications of using a conductive gel. In this study, we developed a cost-effective, easily manufacturable, flexible, robust, and gel-free silver nanowire/polyvinyl butyral (PVB)/melamine sponge (AgPMS) electroencephalogram (EEG) electrode that circumvents problems with hair. Because of surface metallization by the silver nanowires (AgNWs), the sponge has a high conductivity of 917 S/m while its weight remains the same. The flexible sponge framework and self-locking AgNWs combine to give the new electrode remarkable mechanical stability (the conductivity remains unchanged after 10 000 cycles at 10% compression) and the ability to bypass hair. A BCI application based on steady-state visual evoked potential (SSVEP) measurements on hairless skin shows that the BCI accuracy of the new electrode (86%) is approximately the same as that of conventional electrodes supported by a conductive gel (88%). Most importantly, the performance of the AgPMS on hairy skin is not significantly reduced, which indicates that the new electrode can replace conventional electrodes for both hairless and hairy skin BCIs and other EEG applications.
non-line-of-sight imaging using phasor-field virtual wave optics
xiaochun liu et al. 2019
doi.org/10.1038/s41586-019-1461-3
Conventional systems, notes Gutierrez, interpret diffracted light as waves, which can be shaped into images by applying well known mathematical transformations to the light waves propagating through the imaging system.
In the case of non-line-of-sight imaging, the challenge of imaging a hidden scene, says Velten, is resolved by reformulating the non-line-of-sight imaging problem as a wave diffraction problem and then using well-known mathematical transforms from other imaging systems to interpret the waves and reconstruct an image of a hidden scene. By doing this, the new method turns any diffuse wall into a virtual camera.
"What we did was express the problem using waves," says Velten, who also holds faculty appointments in UW-Madison's Department of Electrical and Computer Engineering and the Department of Biostatistics and Medical Informatics, and is affiliated with the Morgridge Institute for Research and the UW-Madison Laboratory for Optical and Computational Instrumentation. "The systems have the same underlying math, but we found that our reconstruction is surprisingly robust, even using really bad data. You can do it with fewer photons."
Using the new approach, Velten's team showed that hidden scenes can be imaged despite the challenges of scene complexity, differences in reflector materials, scattered ambient light and varying depths of field for the objects that make up a scene.
The ability to essentially project a camera from one surface to another suggests that the technology can be developed to a point where it is possible to see around multiple corners: "This should allow us to image around an arbitrary number of corners," says Velten. "To do so, light has to undergo multiple reflections and the problem is how do you separate the light coming from different surfaces? This 'virtual camera' can do that. That's the reason for the complex scene: there are multiple bounces going on and the complexity of the scene we image is greater than what's been done before."
According to Velten, the technique can be applied to create virtual projected versions of any imaging system, even video cameras that capture the propagation of light through the hidden scene. Velten's team, in fact, used the technique to create a video of light transport in the hidden scene, enabling visualization of light bouncing up to four or five times, which, according to the Wisconsin scientist, can be the basis for cameras to see around more than one corner.
The technology could be further and more dramatically improved if arrays of sensors can be devised to capture the light reflected from a hidden scene. The experiments described in the new Nature paper depended on just a single detector.
In medicine, the technology holds promise for things like robotic surgery. Now, the surgeon's field of view is restricted when doing sensitive procedures on the eye, for example, and the technique developed by Velten's team could provide a more complete picture of what's going on around a proce
abstract Non-line-of-sight imaging allows objects to be observed when partially or fully occluded from direct view, by analysing indirect diffuse reflections off a secondary relay surface. Despite many potential applications1,2,3,4,5,6,7,8,9, existing methods lack practical usability because of limitations including the assumption of single scattering only, ideal diffuse reflectance and lack of occlusions within the hidden scene. By contrast, line-of-sight imaging systems do not impose any assumptions about the imaged scene, despite relying on the mathematically simple processes of linear diffractive wave propagation. Here we show that the problem of non-line-of-sight imaging can also be formulated as one of diffractive wave propagation, by introducing a virtual wave field that we term the phasor field. Non-line-of-sight scenes can be imaged from raw time-of-flight data by applying the mathematical operators that model wave propagation in a conventional line-of-sight imaging system. Our method yields a new class of imaging algorithms that mimic the capabilities of line-of-sight cameras. To demonstrate our technique, we derive three imaging algorithms, modelled after three different line-of-sight systems. These algorithms rely on solving a wave diffraction integral, namely the Rayleigh–Sommerfeld diffraction integral. Fast solutions to Rayleigh–Sommerfeld diffraction and its approximations are readily available, benefiting our method. We demonstrate non-line-of-sight imaging of complex scenes with strong multiple scattering and ambient light, arbitrary materials, large depth range and occlusions. Our method handles these challenging cases without explicitly inverting a light-transport model. We believe that our approach will help to unlock the potential of non-line-of-sight imaging and promote the development of relevant applications not restricted to laboratory conditions.
a pilot study for estimating the cardiopulmonary signals of diverse exotic animals using a digital camera
ali al-naji et al. 2020
doi.org/10.3390/s19245445
Filming animals using a high-resolution digital camera installed on a tripod could offer another way for veterinarians to take an animal’s pulse or check its breathing rate.
In the UniSA study, nine species of Adelaide Zoo’s animals were filmed for three minutes, up to 40 metres away, picking up tiny movements in the chest cavity that indicate heart and breathing rates.
The animals filmed included a giant panda, African lion, Sumatran tiger, orangutan, Hamadryas baboon, koala, red kangaroo, alpaca and a little blue penguin.
UniSA Professor Javaan Chahl, a remote sensing engineer and one of the study leads, says the experiment recorded heart and breathing signal from all the animals.
“The study was done without any physical contact with the animals and without disrupting their daily routine,” Prof Chahl says.
“Until now, monitoring vital signs of wild animals has used specialised equipment and usually required disturbing them or their environment.”
abstract Monitoring the cardiopulmonary signal of animals is a challenge for veterinarians in conditions when contact with a conscious animal is inconvenient, difficult, damaging, distressing or dangerous to personnel or the animal subject. In this pilot study, we demonstrate a computer vision-based system and use examples of exotic, untamed species to demonstrate this means to extract the cardiopulmonary signal. Subject animals included the following species: Giant panda (Ailuropoda melanoleuca), African lions (Panthera leo), Sumatran tiger (Panthera tigris sumatrae), koala (Phascolarctos cinereus), red kangaroo (Macropus rufus), alpaca (Vicugna pacos), little blue penguin (Eudyptula minor), Sumatran orangutan (Pongo abelii) and Hamadryas baboon (Papio hamadryas). The study was done without need for restriction, fixation, contact or disruption of the daily routine of the subjects. The pilot system extracts the signal from the abdominal-thoracic region, where cardiopulmonary activity is most likely to be visible using image sequences captured by a digital camera. The results show motion on the body surface of the subjects that is characteristic of cardiopulmonary activity and is likely to be useful to estimate physiological parameters (pulse rate and breathing rate) of animals without any physical contact. The results of the study suggest that a fully controlled study against conventional physiological monitoring equipment is ethically warranted, which may lead to a novel approach to non-contact physiological monitoring and remotely sensed health assessment of animals. The method shows promise for applications in veterinary practice, conservation and game management, animal welfare and zoological and behavioral studies.
new evidence for endemic circulation of ross river virus in the pacific islands and the potential for emergence
colleen lau et al. 2017
doi.org/10.1016/j.ijid.2017.01.041
effects of caffeine and acute aerobic exercise on working memory and caffeine withdrawal
anisa morava et al. 2020
doi.org/10.1038/s41598-019-56251-y
materials
redox-switchable carboranes for uranium capture and release
megan keener et al. 2020
doi.org/10.1038/s41586-019-1926-4
Fifty years ago, scientists hit upon what they thought could be the next rocket fuel. Carboranes — molecules composed of boron, carbon and hydrogen atoms clustered together in three-dimensional shapes — were seen as the possible basis for next-generation propellants due to their ability to release massive amounts of energy when burned.
It was technology that at the time had the potential to augment or even surpass traditional hydrocarbon rocket fuel, and was the subject of heavy investment in the 1950s and 60s.
But things didn’t pan out as expected.
“It turns out that when you burn these things you actually form a lot of sediment,” said Gabriel Ménard, an assistant professor in UC Santa Barbara’s Department of Chemistry and Biochemistry. In addition to other problems found when burning this so-called “zip fuel,” its residue also gummed up the works in rocket engines, and so the project was scrapped.
“So they made these huge stockpiles of these compounds, but they actually never used them,” Ménard said.
Fast forward to today, and these compounds have come back into vogue with a wide range of applications, from medicine to nanoscale engineering. For Ménard and fellow UCSB chemistry professor Trevor Hayton, as well as Tel Aviv University chemistry professor Roman Dobrovetsky, carboranes could hold the key to more efficient uranium ion extraction. And that, in turn, could enable things like better nuclear waste reprocessing and uranium (and other metal) recovery from seawater.
Their research — the first example of applying electrochemical carborane processes to uranium extraction — is published in a paper (link) that appears in the journal Nature.
Key to this technology is the versatility of the cluster molecule. Depending on their compositions these structures can resemble closed cages, or more open nests, due to control of the compound’s redox activity — its readiness to donate or gain electrons. This allows for the controlled capture and release of metal ions, which in this study was applied to uranium ions.
“The big advancement here is this ‘catch and release’ strategy where you can switch between two states, where one state binds the metal and another state releases the metal,” Hayton said.
Conventional processes, such as the popular PUREX process that extracts plutonium and uranium, rely heavily on solvents, extractants and extensive processing.
“Basically, you could say it’s wasteful,” Ménard said. “In our case, we can do this electrochemically — we can capture and release the uranium with the flip of a switch.
“What actually happens,” added Ménard, “is that the cage opens up.” Specifically, the formerly closed ortho-carborane becomes an opened nido- (“nest”) carborane capable of capturing the positively-charged uranium ion.
Conventionally, the controlled release of extracted uranium ions, however, is not as straightforward and can be somewhat messy. According to the researchers, such methods are “less established and can be difficult, expensive and or destructive to the initial material.”
But here, the researchers have devised a way to reliably and efficiently flip back and forth between open and closed carboranes, using electricity. By applying an electrical potential using an electrode dipped in the organic portion of a biphasic system, the carboranes can receive and donate the electrons needed to open and close and capture and release uranium, respectively.
“Basically you can open it up, capture uranium, close it back up and then release uranium,” Ménard said. The molecules can be used multiple times, he added.
This technology could be used for several applications that require the extraction of uranium and by extension, other metal ions. One area is nuclear reprocessing, in which uranium and other radioactive “trans-uranium” elements are extracted from spent nuclear material for storage and reuse (the PUREX process).
“The problem is that these trans-uranium elements are very radioactive and we need to be able to store these for a very long time because they’re basically very dangerous,” Ménard said. This electrochemical method could allow for the separation of uranium from plutonium, similar to the PUREX process, he explained. The extracted uranium could then be enriched and put back into the reactor; the other high-level waste can be transmuted to reduce their radioactivity.
Additionally, the electrochemical process could also be applied to uranium extraction from seawater, which would ease pressure on the terrestrial mines where all uranium is currently sourced.
“There’s about a thousand times more dissolved uranium in the oceans than there are in all the land mines,” Ménard said. Similarly, lithium — another valuable metal that exists in large reserves in seawater — could be extracted this way, and the researchers plan to take this research direction in the near future.
“This gives us another tool in the toolbox for manipulating metal ions and processing nuclear waste or doing metal capture out of oceans,” Hayton said. “It’s a new strategy and new method to achieve these types of transformations.”
abstract The uranyl ion (UO22+; U(VI) oxidation state) is the most common form of uranium found in terrestrial and aquatic environments and is a central component in nuclear fuel processing and waste remediation efforts. Uranyl capture from either seawater or nuclear waste has been well studied and typically relies on extremely strong chelating/binding affinities to UO22+ using chelating polymers12,13, porous inorganic3,4,16 or carbon-based17,18 materials, as well as homogeneous19 compounds. By contrast, the controlled release of uranyl after capture is less established and can be difficult, expensive or destructive to the initial material13,9. Here we show how harnessing the redox-switchable chelating and donating properties of an ortho-substituted closo-carborane (1,2-(Ph2PO)2-1,2-C2B10H10) cluster molecule can lead to the controlled chemical or electrochemical capture and release of UO22+ in monophasic (organic) or biphasic (organic/aqueous) model solvent systems. This is achieved by taking advantage of the increase in the ligand bite angle when the closo-carborane is reduced to the nido-carborane, resulting in C–C bond rupture and cage opening. The use of electrochemical methods for uranyl capture and release may complement existing sorbent and processing systems.
additive manufacturing of cellulosic materials with robust mechanics and antimicrobial functionality
sebastian w. pattinson, a. john hart 2017
doi.org/10.1002/admt.201600084
processing bulk natural wood into a high-performance structural material
jianwei song et al. 2018
doi.org/10.1038/nature25476
self-assembled nanotextures impart broadband transparency to glass windows and solar cell encapsulants
andreas c. liapis et al. 2017
doi.org/10.1063/1.5000965
achieving ultralow wear with stable nanocrystalline metals
john f. curry et al. 2018
doi.org/10.1002/adma.201802026
ionic modification turns commercial rubber into a self-healing material
amit das et al. 2015
doi.org/10.1021/acsami.5b05041
iron-based shape memory alloy strips for strengthening rc members: material behavior and characterization
moslem shahverdi et al. 2018
doi.org/10.1016/j.conbuildmat.2018.04.057
•Production of iron-based shape memory alloy (Fe-SMA) strips at industrial level for civil engineering applications.
•Fe-SMA strips were characterized for application as externally fixed reinforcements for RC members.
•The relaxation behavior of Fe-SMA strips for durations of more than 1000 h was studied.
•The effects of different parameters on the recovery stress of Fe-SMA strips are investigated.
•Long Fe-SMA strips are activated in air by resistive heating.
Shape memory alloys (SMAs), in the form of bars and strips, can be used as prestressing elements in new reinforced concrete (RC) members or for strengthening existing RC structures, owing to their special characteristic known as the shape memory effect (SME). When the SME comes into play, the material returns to its initial shape upon heating after having been deformed at ambient temperatures. If a return to the initial shape is prevented by mechanical fixation, stress develops in the SMA. A cost-effective iron-based SMA (Fe-SMA) has been developed for application in civil engineering structures. The composition of the developed alloy is Fe–17Mn–5Si–10Cr–4Ni–1(V,C) (mass%). This Fe-SMA exhibits high tensile strength, excellent shape recovery stress (prestress force), and high elastic stiffness. Moreover, its material cost is low and it is easier to manufacture than nickel-titanium (NiTi) alloys. Recently, Fe-SMA strip production has been started at an industrial scale. In this study, the experimentally determined properties of such industrially produced Fe-SMA strips are presented, and their recovery stress and recovery strain have been measured. The effects of prestraining and maximum heating temperature on the obtained recovery stress have been studied. These Fe-SMA strips can be used as external end-fixed reinforcements to strengthen RC structures.
phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in roman marine concrete
marie d. jackson et al. 2017
doi.org/10.2138/am-2017-5993CCBY
extra strengthening and work hardening in gradient nanotwinned metals
zhao cheng et al. 2018
doi.org/10.1126/science.aau1925
varying the spacing between twin boundaries, as opposed to maintaining consistent spacing throughout, produces dramatic improvements in a metal’s strength and rate of work hardening — the extent to which a metal strengthens when deformed.
Huajian Gao, a professor in Brown’s School of Engineering who co-led the work, says the research could point toward new manufacturing techniques for high-performance materials.
“This work deals with what’s known as a gradient material, meaning a material in which there’s some gradual variation in its internal makeup,” Gao said. “Gradient materials are a hot research area because they often have desirable properties compared to homogeneous materials. In this case, we wanted to see if a gradient in nanotwin spacing produced new properties.”
Gao and his colleagues have already shown that nanotwins themselves can improve material performance. Nanotwinned copper, for example, has shown to be significantly stronger than standard copper, with an unusually high resistance to fatigue. But this is the first study to test the effects of variable nanotwin spacing.
Gao and his colleagues created copper samples using four distinct components, each with different nanotwin boundary spacing. Spacings ranging from 29 nanometers between boundaries to 72 nanometers. The copper samples were comprised of different combinations of the four components arranged in different orders across the thickness of the sample. The researchers then tested the strength of each composite sample, as well as the strength of each of the four components.
The tests showed that all of the composites were stronger than the average strength of the four components from which they were made. Remarkably, one of the composites was actually stronger than the strongest of its constituent components.
“To give an analogy, we think of a chain as being only as strong as its weakest link,” Gao said. “But here, we have a situation in which our chain is actually stronger than its strongest link, which is really quite amazing.”
Other tests showed that the composites also had higher rates of work hardening than the average of their constituent components.
To understand the mechanism behind these increases in performance, the researchers used computer simulations of their samples’ atomic structure under strain. At the atomic level, metals respond to strain through the motion of dislocations — line defects in the crystalline structure where atoms are pushed out of place. The way in which those dislocations grow and interact with each other is what determines a metal’s strength.
The simulations revealed that the density of dislocations is much higher in the gradient copper than in a normal metal.
“We found a unique type of dislocation we call bundles of concentrated dislocations, which lead to dislocations an order of magnitude denser than normal,” Gao said. “This type of dislocation doesn’t occur in other materials and it’s why this gradient copper is so strong.”
Gao said that while the research team used copper for this study, nanotwins can be produced in other metals as well. So it’s possible that nanotwin gradients could improve the properties of other metals.
abstract Gradient structures ubiquitously exist in natural materials such as bone, shells, and trees. Microstructural gradients are increasingly being introduced into a wide range of engineering materials, providing them with enhanced strength, hardness, work hardening, ductility, and fatigue resistance through deformation mechanisms that are distinct from those operating in gradient-free counterparts.
self‐assembly of large‐area 2d polycrystalline transition metal carbides for hydrogen electrocatalysis
xining zang et al. 2018
doi.org/10.1002/adma.201805188
using gelatin
We believe that as gelatin dries, it self-assembles layer by layer
Platinum is expensive, so it would be desirable to find other alternative materials to replace it," said senior author Liwei Lin, professor of mechanical engineering at UC Berkeley. "We are actually using something similar to the Jell-O that you can eat as the foundation, and mixing it with some of the abundant earth elements to create an inexpensive new material for important catalytic reactions."
This study was made available online in Oct. 2018 in the journal Advanced Materials ahead of final publication in print on Dec. 13.
A zap of electricity can break apart the strong bonds that tie water molecules together, creating oxygen and hydrogen gas, the latter of which is an extremely valuable source of energy for powering hydrogen fuel cells. Hydrogen gas can also be used to help store energy from renewable yet intermittent energy sources like solar and wind power, which produce excess electricity when the sun shines or when the wind blows, but which go dormant on rainy or calm days.
But simply sticking an electrode in a glass of water is an extremely inefficient method of generating hydrogen gas. For the past 20 years, scientists have been searching for catalysts that can speed up this reaction, making it practical for large-scale use.
"The traditional way of using water gas to generate hydrogen still dominates in industry. However, this method produces carbon dioxide as byproduct," said first author Xining Zang, who conducted the research as a graduate student in mechanical engineering at UC Berkeley. "Electrocatalytic hydrogen generation is growing in the past decade, following the global demand to lower emissions. Developing a highly efficient and low-cost catalyst for electrohydrolysis will bring profound technical, economical and societal benefit."
To create the catalyst, the researchers followed a recipe nearly as simple as making Jell-O from a box. They mixed gelatin and a metal ion -- either molybdenum, tungsten or cobalt -- with water, and then let the mixture dry.
"We believe that as gelatin dries, it self-assembles layer by layer," Lin said. "The metal ion is carried by the gelatin, so when the gelatin self-assembles, your metal ion is also arranged into these flat layers, and these flat sheets are what give Jell-O its characteristic mirror-like surface."
Heating the mixture to 600 degrees Celsius triggers the metal ion to react with the carbon atoms in the gelatin, forming large, nanometer-thin sheets of metal carbide. The unreacted gelatin burns away.
The researchers tested the efficiency of the catalysts by placing them in water and running an electric current through them. When stacked up against each other, molybdenum carbide split water the most efficiently, followed by tungsten carbide and then cobalt carbide, which didn't form thin layers as well as the other two. Mixing molybdenum ions with a small amount of cobalt boosted the performance even more.
"It is possible that other forms of carbide may provide even better performance," Lin said.
The two-dimensional shape of the catalyst is one of the reasons why it is so successful. That is because the water has to be in contact with the surface of the catalyst in order to do its job, and the large surface area of the sheets mean that the metal carbides are extremely efficient for their weight.
Because the recipe is so simple, it could easily be scaled up to produce large quantities of the catalyst, the researchers say.
"We found that the performance is very close to the best catalyst made of platinum and carbon, which is the gold standard in this area," Lin said. "This means that we can replace the very expensive platinum with our material, which is made in a very scalable manufacturing process."
abstract Low‐dimensional (0/1/2 dimension) transition metal carbides (TMCs) possess intriguing electrical, mechanical, and electrochemical properties, and they serve as convenient supports for transition metal catalysts. Large‐area single‐crystalline 2D TMC sheets are generally prepared by exfoliating MXene sheets from MAX phases. Here, a versatile bottom‐up method is reported for preparing ultrathin TMC sheets (≈10 nm in thickness and >100 μm in lateral size) with metal nanoparticle decoration. A gelatin hydrogel is employed as a scaffold to coordinate metal ions (Mo5+, W6+, Co2+), resulting in ultrathin‐film morphologies of diverse TMC sheets. Carbonization of the scaffold at 600 °C presents a facile route to the corresponding MoCx, WCx, CoCx, and to metal‐rich hybrids (Mo2−xWxC and W/Mo2C–Co). Among these materials, the Mo2C–Co hybrid provides excellent hydrogen evolution reaction (HER) efficiency (Tafel slope of 39 mV dec−1 and 48 mVj = 10 mA cm‐2 in overpotential in 0.5 m H2SO4). Such performance makes Mo2C–Co a viable noble‐metal‐free catalyst for the HER, and is competitive with the standard platinum on carbon support. This template‐assisted, self‐assembling, scalable, and low‐cost manufacturing process presents a new tactic to construct low‐dimensional TMCs with applications in various clean‐energy‐related fields.
renewable fertiliser synthesis
catalyst-free, highly selective synthesis of ammonia from nitrogen and water by a plasma electrolytic system
ryan hawtof et al. 2018
doi.org/10.1126/sciadv.aat5778
But while we've been producing ammonia at a large scale since the 1930s, it has been accomplished mainly in hulking chemical plants requiring vast amounts of hydrogen gas from fossil fuels -- making ammonia among the most energy-intensive among all large-volume chemicals.
A pair of researchers at Case Western Reserve University -- one an expert in electro-chemical synthesis, the other in applications of plasmas -- are working on fixing that.
Researchers Julie Renner and Mohan Sankaran have come up with a new way to create ammonia from nitrogen and water at low temperature and low pressure. They've done it successfully so far in a laboratory without using hydrogen or the solid metal catalyst necessary in traditional processes.
"Our approach -- an electrolytic process with a plasma -- is completely new," said Mohan Sankaran, the Goodrich Professor of Engineering Innovation at the Case School of Engineering.
Plasmas, often referred to as the fourth state of matter (apart from solid, liquid or gas), are ionized clouds of gas, consisting of positive ions and free electrons, which give it the unique ability to activate chemical bonds, including the rather challenging nitrogen molecule, at room temperature.
Renner, a Climo Assistant Professor in the Chemical and Biomolecular Engineering Department, added that because this new process doesn't need high pressure or high temperature or hydrogen, it makes it scalable -- "the ideal kind of technology for a much smaller plant, one with high potential to be powered by renewable energy."
The results of their two-year collaboration were published this month in the journal Science Advances.
History lesson: The Haber-Bosch process
Virtually all commercial ammonia is made from nitrogen and hydrogen, using an iron catalyst at high temperature and pressure.
German physical chemist Fritz Haber received the Nobel Prize for Chemistry in 1918 for developing this process, which made manufacturing ammonia economically feasible.
But the process became more economically profitable when industrial chemist Carl Bosch (who also won a Nobel Prize in 1931) brought the method into a large-scale system. The process was further propelled by a second innovation: the development of steam methane reforming that made hydrogen more accessible and less expensive.
So, what became known as the Haber-Bosch process became the go-to global method for fixing nitrogen and hydrogen to make ammonia.
But Haber-Bosch was never the only approach to nitrogen fixation, it was just the turn-of-the-century winner.
A new, old method rises
Renner and Sankaran have resurrected an element from a little-known Norwegian method that predated Haber-Bosch (the Birkeland-Eyde process) which reacted nitrogen and oxygen to produce nitrates, another chemical that can be used in agriculture. That process lost out to Haber-Bosch mostly because it required even more energy in the form of electricity, a limited resource in the early 20th century.
"Our approach is similar to electrolytic synthesis of ammonia, which has gained interest as an alternative to Haber-Bosch because it can be integrated with renewable energy," Sankaran said. "However, like the Birkeland-Eyde process, we use a plasma, which is energy intensive. Electricity is still a barrier, but less so now, and with the increase in renewables, it may not be a barrier at all in the future.
"And perhaps most significantly, our process does not produce hydrogen gas," he said. "This has been the major bottleneck of other electrolytic approaches to forming ammonia from water (and nitrogen), the undesirable formation of hydrogen."
The Renner-Sankaran process also does not use a solid metal catalyst that could be one of the reasons ammonia is obtained instead of hydrogen.
"In our system, the ammonia is formed at the interface of a gas plasma and liquid water surface and forms freely in solution," Sankaran said.
So far, the "table-top batches" of ammonia produced by the duo have been very small and the energy efficiency is still less than Haber-Bosch. But with continued optimization, their discovery and development of a new process could someday lead to smaller, more localized ammonia plants which use green energy
abstract There is a growing need for scalable ammonia synthesis at ambient conditions that relies on renewable sources of energy and feedstocks to replace the Haber-Bosch process. Electrically driven approaches are an ideal strategy for the reduction of nitrogen to ammonia but, to date, have suffered from low selectivity associated with the catalyst. Here, we present a hybrid electrolytic system characterized by a gaseous plasma electrode that facilitates the study of ammonia formation in the absence of any material surface. We find record-high faradaic efficiency (up to 100%) for ammonia from nitrogen and water at atmospheric pressure and temperature with this system. Ammonia measurements under varying reaction conditions in combination with scavengers reveal that the unprecedented selectivity is achieved by solvated electrons produced at the plasma-water interface, which react favorably with protons to produce the key hydrogen radical intermediate. Our results demonstrate that limitations in selectivity can be circumvented by using catalyst-free solvated electron chemistry. In the absence of adsorption steps, the importance of controlling proton concentration and transport is also revealed.
cooking chemistry transforms proteins into high-strength adhesives
jessica k. román, jonathan j. wilker 2019
doi.org/10.1021/jacs.8b12150
Wilker studies how marine animals, such as oysters and mussels, create natural adhesives. Unlike most glues you'd find in a hardware store, these adhesives are non-toxic, and many hold up underwater. While trying to re-create a new glue in his lab one day, Wilker noticed something strange.
"Things were sticking when they shouldn't have been," he said. "We found that the components being used, proteins and sugar, were reacting and turning into an adhesive."
This is the essence of Maillard chemistry, or "cooking chemistry," for those of us who aren't chemists. It happens when you grill a streak or bake bread in the oven; after a while, the edges start to brown and a savory smell fills the air. Chemically, sugars and proteins are combining to create aromatic compounds.
Usually, it takes heat to kick off this process, but Maillard chemistry is a whole class of messy reactions, and it can happen a few different ways. Products of each reaction get involved in their own reactions and can release chemicals that we experience as flavors. Describing the Maillard reaction in detail would take up an entire book alone, according to PBS.
"When foods brown, certain molecules are linking together. Proteins can connect to one another by reacting with sugars," Wilker said. "When sea creatures make their adhesives, they are also cross-linking proteins together. They use totally different chemistry, but the idea is somewhat similar; cross-linking proteins can create an adhesive."
This new soy-based adhesive doesn't hold up well under water, so it probably isn't a perfect replacement for the toxic glues used in plywood and chipboard (the fumes from which, when used to build houses, can be breathed in by homeowners for many years). However, it may find use in packaging of organic-certified food products.
"Food packaging usually relies on typical petroleum-based adhesives, which can leach out toxins," Wilker said.
Not only is this new adhesive made from food components, but it's even stronger than Gorilla Glue on wood. On aluminum, it's about the same. The findings were published recently in the Journal of the American Chemical Society.
To test the strength of the adhesive, Wilker's team glued two pieces of wood or aluminum together. The far ends have a hole for a pin, and a machine pulls them in opposite directions to test their strength. The new adhesive was so strong on wood that the pin ripped through the hole.
Although the soy-based adhesive was pretty strong, the team achieved even better results with a different protein, bovine serum albumin (BSA). BSA is a generic protein often used in labs for experiments. It's cheap for researchers, but not cheap enough to make a BSA-based adhesive affordable on a large commercial scale.
"If you want to break into the adhesive market, your product needs to be cheap, high-performance, and the material also has to be available on large scales," Wilker said. "This new soy-based adhesive may be able to hit these requirements while also being grown renewably."
abstract In prior generations, proteins were taken from horses and other animals to make glues. Petroleum-derived polymers including epoxies and cyanoacrylates have since replaced proteins owing to improved performance. These modern materials come at a cost of toxicity as well as being derived from limited resources. Ideally, replacement adhesives will be made from benign, cheap, and renewable feedstocks. Such a transition to biobased materials, however, will not occur until similar or improved performance can be achieved. We have discovered that coupling of proteins and sugars gives rise to strong adhesives. An unexpected connection was made between adhesion and Maillard chemistry, known to be at the heart of cooking foods. Cross-linked proteins bonded metal and wood with high strengths, in some cases showing forces exceeding those withstood by the substrates themselves. Simple cooking chemistry may provide a route to future high-performance materials derived from low-cost, environmentally benign components.
squid-inspired tandem repeat proteins: functional fibers and films
abdon pena-francesch, melik c. demirel
doi.org/10.3389/fchem.2019.00069
"Nature produces a variety of smart materials capable of environmental sensing, self-healing and exceptional mechanical function. These materials, or biopolymers, have unique physical properties that are not readily found in synthetic polymers like plastic. Importantly, biopolymers are sustainable and can be engineered to enhance their physical properties," explains Demirel.
The oceans, which have borne the brunt of plastic pollution, are at the center of the search for sustainable alternatives. A newly-discovered protein from squid ring teeth (SRT) -- circular predatory appendages located on the suction cups of squid, used to strongly grasp prey -- has gained interest because of its remarkable properties and sustainable production.
The elasticity, flexibility and strength of SRT-based materials, as well as their self-healing, optical, and thermal and electrical conducting properties, can be explained by the variety of molecular arrangements they can adopt. SRT proteins are composed of building blocks arranged in such a way that micro-phase separation occurs. This is a similar situation to oil and water but on a much smaller, nano-scale. The blocks cannot separate completely to produce two distinct layers, so instead molecular-level shapes are created, such as repeating cylindrical blocks, disordered tangles or ordered layers. The shapes formed dictate the property of the material and scientists have experimented with these to produce SRT-based products for a variety of uses.
In the textiles industry, SRT protein could address one of the main sources of microplastic pollution by providing an abrasion-resistant coating that reduces microfiber erosion in washing machines. Similarly, a self-healing SRT protein coating could increase the longevity and safety of damage-prone biochemical implants, as well as garments tailored for protection against chemical and biological warfare agents.
It is even possible to interleave multiple layers of SRT proteins with other compounds or technology, which could lead to the development of 'smart' clothes that can protect us from pollutants in the air while also keeping an eye on our health. The optical properties of SRT-based materials mean these clothes could also display information about our health or surroundings. Flexible SRT-based photonic devices -- components that create, manipulate or detect light, such as LEDs and optical displays, which are typically manufactured with hard materials like glass and quartz -- are currently in development.
"SRT photonics are biocompatible and biodegradable, so could be used to make not only wearable health monitors but also implantable devices for biosensing and biodetection," adds Demirel.
No squid was harmed in the making of this film
One of the main advantages of SRT-based materials over synthetic materials and plastics made from fossil fuels are its eco-credentials. SRT proteins are cheaply and easily produced from renewable resources and researchers have found a way of producing it without catching a squid. "We don't want to deplete natural squid resources and hence we produce these proteins in genetically modified bacteria. The process is based on fermentation and uses sugar, water, and oxygen to produce biopolymers," explains Demirel.
It is hoped that the SRT-based prototypes will soon become available more widely, but more development is needed.
Demirel explains, "Scaling up these materials requires additional work. We are now working on the processing technology of these materials so that we can make them available in industrial manufacturing processes."
abstract Production of repetitive polypeptides that comprise one or more tandem copies of a single unit with distinct amorphous and ordered regions have been an interest for the last couple of decades. Their molecular structure provides a rich architecture that can micro-phase-separate to form periodic nanostructures (e.g., lamellar and cylindrical repeating phases) with enhanced physicochemical properties via directed or natural evolution that often exceed those of conventional synthetic polymers. Here, we review programmable design, structure, and properties of functional fibers and films from squid-inspired tandem repeat proteins, with applications in soft photonics and advanced textiles among others.
nanoparticle-enabled phase control for arc welding of unweldable aluminum alloy 7075
maximilian sokoluk et al. 2019
doi.org/10.1038/s41467-018-07989-y
bacterially produced, nacre‐inspired composite materials
ewa m. spiesz et al. 2019
doi.org/10.1002/smll.201805312
One natural substance scientists have looked to in creating synthetic materials is nacre, also known as mother-of-pearl. An exceptionally tough, stiff material produced by some mollusks and serving as their inner shell layer, it also comprises the outer layer of pearls, giving them their lustrous shine.
But while nacre's unique properties make it an ideal inspiration in the creation of synthetic materials, most methods used to produce artificial nacre are complex and energy intensive.
Now, a biologist at the University of Rochester has invented an inexpensive and environmentally friendly method for making artificial nacre using an innovative component: bacteria. The artificial nacre created by Anne S. Meyer, an associate professor of biology at Rochester, and her colleagues is made of biologically produced materials and has the toughness of natural nacre, while also being stiff and, surprisingly, bendable.
The method used to create the novel material could lead to new applications in medicine, engineering -- and even constructing buildings on the moon.
IMPRESSIVE MECHANICAL PROPERTIES
The impressive mechanical properties of natural nacre arise from its hierarchical, layered structure, which allows energy to disperse evenly across the material. In a paper published in the journal Small, Meyer and her colleagues outline their method of using two strains of bacteria to replicate these layers. When they examined the samples under an electron microscope, the structure created by the bacteria was layered similarly to nacre produced naturally by mollusks.
Although nacre-inspired materials have been created synthetically before, the methods used to make them typically involve expensive equipment, extreme temperatures, high-pressure conditions, and toxic chemicals, Meyer says. "Many people creating artificial nacre use polymer layers that are only soluble in nonaqueous solutions, an organic solvent, and then they have this giant bucket of waste at the end of the procedure that has to be disposed of."
To produce nacre in Meyer's lab, however, all researchers have to do is grow bacteria and let it sit in a warm place.
FROM BACTERIA TO NACRE
In order to make the artificial nacre, Meyer and her team create alternating thin layers of crystalized calcium carbonate -- like cement -- and sticky polymer. They first take a glass or plastic slide and place it in a beaker containing the bacteria Sporosarcina pasteurii, a calcium source, and urea (in the human body, urea is the waste product excreted by the kidneys during urination). This combination triggers the crystallization of calcium carbonate. To make the polymer layer, they place the slide into a solution of the bacteria Bacillus licheniformis, then let the beaker sit in an incubator.
Right now it takes about a day to build up a layer, approximately five micrometers thick, of calcium carbonate and polymer. Meyer and her team are currently looking at coating other materials like metal with the nacre, and "we're trying new techniques to make thicker, nacre-like materials faster and that could be the entire material itself," Meyer says.
BUILDING HOUSES ON THE MOON
One of the most beneficial characteristics of the nacre produced in Meyer's lab is that it is biocompatible -- made of materials the human body produces or that humans can eat naturally anyway. This makes the nacre ideal for medical applications like artificial bones and implants, Meyer says. "If you break your arm, for example, you might put in a metal pin that has to be removed with a second surgery after your bone heals. A pin made out of our material would be stiff and tough, but you wouldn't have to remove it."
And, while the material is tougher and stiffer than most plastics, it is very lightweight, a quality that is especially valuable for transportation vehicles like airplanes, boats, or rockets, where every extra pound means extra fuel. Because the production of bacterial nacre doesn't require any complex instruments, and the nacre coating protects against chemical degradation and weathering, it holds promise for civil engineering applications like crack prevention, protective coatings for erosion control, or for conservation of cultural artifacts, and could be useful in the food industry, as a sustainable packaging material.
The nacre might also be an ideal material to build houses on the moon and other planets: the only necessary "ingredients" would be an astronaut and a small tube of bacteria, Meyer says. "The moon has a large amount of calcium in the moon dust, so the calcium's already there. The astronaut brings the bacteria, and the astronaut makes the urea, which is the only other thing you need to start making calcium carbonate layers."
Even beyond its qualities as an ideal structural material, nacre itself -- as any pearl jewelry owner knows -- is "very beautiful," Meyer says, owing to its stacked layers. Each stacked layer is approximately the same wavelength as visible light. When light hits the nacre, "the wavelengths of light interact with these layers of the same height so it bounces back off in the same wavelength as visible light." While the bacterial nacre does not interact with visible light because the layers are thicker than natural nacre, it could interact with infrared wavelengths and bounce infrared off itself, Meyer says, which "may offer unique optical properties."
abstract The impressive mechanical properties of natural composites, such as nacre, arise from their multiscale hierarchical structures, which span from nano‐ to macroscale and lead to effective energy dissipation. While some synthetic bioinspired materials have achieved the toughness of natural nacre, current production methods are complex and typically involve toxic chemicals, extreme temperatures, and/or high pressures. Here, the exclusive use of bacteria to produce nacre‐inspired layered calcium carbonate‐polyglutamate composite materials that reach and exceed the toughness of natural nacre, while additionally exhibiting high extensibility and maintaining high stiffness, is introduced. The extensive diversity of bacterial metabolic abilities and the possibility of genetic engineering allows for the creation of a library of bacterially produced, cost‐effective, and eco‐friendly composite materials.
piece by piece-electrochemical synthesis of individual nanoparticles and their performance in orr electrocatalysis
mathies v. evers et al. 2019
doi.org/10.1002/anie.201813993
Researchers at Ruhr-Universität Bochum and the Fritz Haber Institute Berlin have developed a new method of using rare and expensive catalysts as sparingly as possible. They enclosed a precious metal salt in outer shells, tiny micelles, and had them strike against a carbon electrode, thus coating the surface with nanoparticles of the precious metal contained in the micelles. At the same time, the team was able to precisely analyse how much of the metal was deposited. The researchers then showed that the electrode coated in this manner could efficiently catalyse the oxygen reduction, which is the limiting chemical process in fuel cells.
The team led by Professor Kristina Tschulik and Mathies Evers from the Bochum Research Group for Electrochemistry and Nanoscale Materials describes the process in the journal Angewandte Chemie, published online in advance on 11 April 2019.
Producing particles of the same size
The research group produced the gold nanoparticles with the help of micelles. The particles initially consisted of a precursor substance, chloroauric acid, which was wrapped in an outer polymer shell. The benefit: "When we produce gold nanoparticles using micelles, the nanoparticles are all of an almost identical size," says Kristina Tschulik, a Principal Investigator of the Cluster of Excellence Ruhr Explores Solvation (Resolv). Only a certain load of the precursor material, from which a single particle of a certain size is produced, fits inside the small micelles. "As particles of different sizes have different catalytic properties, it is important to control the particle size by means of the load quantity of the micelle," adds Tschulik.
Uniform coating, even on complex surfaces
To coat the cylindrical electrode, the researchers immersed it in a solution containing the loaded micelles and applied a voltage to the electrode. The random motion of the micelles in the solution caused them to strike against the electrode surface over time. There, the outer shell burst open and the gold ions from the chloroauric acid reacted to form elemental gold, which adhered to the electrode surface as a uniform layer of nanoparticles. "Only flat substrates can be coated uniformly with nanoparticles using standard methods," explains Tschulik. "Our process means that even complex surfaces can be loaded uniformly with a catalyst."
Separated quantity precisely controllable
While the gold ions from the chloroauric acid react to form elemental gold, electrons flow. By measuring the resulting current, the chemists can determine exactly how much material was used to coat the electrode. At the same time, the method registers the impact of each individual particle and its size.
The researchers successfully tested the oxygen reduction reaction of the electrodes coated using the new process. They achieved an activity as high as that of naked gold nanoparticles without an outer shell. Due to the uniform coating of the surface, they also observed a reaction rate almost as high as that of electrodes completely covered with gold and solid gold electrodes at just eleven percent coverage.
abstract The impact of individual HAuCl4 nanoreactors is measured electrochemically, which provides operando insights and precise control over the modification of electrodes with functional nanoparticles of well‐defined size. Uniformly sized micelles are loaded with a dissolved metal salt. These solution‐phase precursor entities are then reduced electrochemically—one by one—to form nanoparticles (NPs). The charge transferred during the reduction of each micelle is measured individually and allows operando sizing of each of the formed nanoparticles. Thus, particles of known number and sizes can be deposited homogenously even on nonplanar electrodes. This is demonstrated for the decoration of cylindrical carbon fibre electrodes with 25±7 nm sized Au particles from HAuCl4‐filled micelles. These Au NP‐decorated electrodes show great catalyst performance for ORR (oxygen reduction reaction) already at low catalyst loadings. Hence, collisions of individual precursor‐filled nanocontainers are presented as a new route to nanoparticle‐modified electrodes with high catalyst utilization.
ultrafast laser welding of ceramics
e. h. penilla et al. 2019
doi.org/10.1126/science.aaw6699
"Right now there is no way to encase or seal electronic components inside ceramics because you would have to put the entire assembly in a furnace, which would end up burning the electronics," Garay said.
Garay, Aguilar and colleagues' solution was to aim a series of short laser pulses along the interface between two ceramic parts so that heat builds up only at the interface and causes localized melting. They call their method ultrafast pulsed laser welding.
To make it work, the researchers had to optimize two aspects: the laser parameters (exposure time, number of laser pulses, and duration of pulses) and the transparency of the ceramic material. With the right combination, the laser energy couples strongly to the ceramic, allowing welds to be made using low laser power (less than 50 watts) at room temperature.
"The sweet spot of ultrafast pulses was two picoseconds at the high repetition rate of one megahertz, along with a moderate total number of pulses. This maximized the melt diameter, minimized material ablation, and timed cooling just right for the best weld possible," Aguilar said.
"By focusing the energy right where we want it, we avoid setting up temperature gradients throughout the ceramic, so we can encase temperature-sensitive materials without damaging them," Garay said.
As a proof of concept, the researchers welded a transparent cylindrical cap to the inside of a ceramic tube. Tests showed that the welds are strong enough to hold vacuum.
"The vacuum tests we used on our welds are the same tests that are used in industry to validate seals on electronic and optoelectronic devices," said first author Elias Penilla, who worked on the project as a postdoctoral researcher in Garay's research group at UC San Diego.
The process has so far only been used to weld small ceramic parts that are less than two centimeters in size. Future plans will involve optimizing the method for larger scales, as well as for different types of materials and geometries.
unconventional tissue engineering materials in disguise
nguyen and camci-unal 2019
doi.org/10.1016/j.tibtech.2019.07.014
turning to nature and trying to see what exists and how can we utilize them for tissue regeneration."
The scaffolds used in tissue engineering help position cells in a particular pattern, which in turn allows them to become functional in a tissue-specific manner. However, finding the perfect scaffold that is porous and biocompatible with mechanical strength is not easy. For that reason, scientists are now borrowing ready-made natural materials for a cost-efficient and sustainable approach.
"We're essentially trying to simplify the process and trying to use readily available materials that can fit in the tissue during the application," says Camci-Unal.
For example, a research team at Worcester Polytechnic Institute is now hacking into different plants' unique vein systems, such as spinach. Spinach's dense network of veins resembles the vasculature network of the human heart. By washing out the plant cells and leaving the plant wall matrix behind, the researchers can grow cardiac tissue on spinach skeletons.
Other researchers have explored a variety of other materials. Tofu is being utilized as a protein-rich scaffold to help wound healing through the promotion of cell adhesion. Incorporating calcium-rich eggshells to reinforce scaffolding materials can boost bone healing and nerve tissue regeneration. Some studies have drawn inspiration from origami to construct 3D paper scaffolds to grow bone tissue.
"People have been using paper for so many different applications for thousands of years," says Camci-Unal. "But it wasn't until 10 years ago that we started using them as tissue-engineering scaffolds for cell culture platforms. I think sometimes simple things are just overlooked."
Scientists' recent ventures into unconventional biomaterials show promising results but also need further investigation in vivo. While these biomaterials improve the functionality, scalability, and sustainability of current tissue engineering and potentially provide a novel approach to serve a broad spectrum of diseases, there is still more work that needs to be done.
Before clinical translation is possible, Camci-Unal says, standard protocols, biomaterial efficacy, and patient safety need to be established. This is particularly true because the field often overlooks and understudies many of these biomaterials. "We're not familiar to some of the materials because it hasn't been studied extensively yet," she says. "We're not aware of what the disadvantages may be, or there are other great advantages that we're not aware of yet."
One other benefit of these unconventional and naturally derived materials is that they can simplify tissue-engineering processes and lower the cost of study and environmental impacts, making this kind of research more globally accessible. "We want to make science available to anybody in the world, not just to highly equipped and highly resourced facilities," says Camci-Unal. "We're trying to develop biomaterials for all."
abstract Tissue engineering faces a recurring challenge in the transformation of biomaterials into 3D constructs that mimic the biological, chemical, and mechanical features of native tissues. Some of the conventional approaches can be sophisticated and involve extensive material processing and high-cost fabrication procedures. Despite tremendous strides in biomaterials discovery and characterization, the functional and manufacturing limitations have led to the innovation of novel biomimetic techniques that borrow from nature, human-made commodities, and other parts of life to overcome the challenges in tissue engineering and regenerative medicine. This review explores engineering strategies that involve unusual materials for improved functionality, scalability, sustainability, and cost-efficiency. The biomaterials discussed are globally accessible resources and can serve across a wide spectrum of biomedical research areas.
reversible adhesion to rough surfaces both in and out of water, inspired by the clingfish suction disc
jessica alexandra sandoval et al. 2019
doi.org/10.1088/1748-3190/ab47d1
Clingfish are small fish widespread in tropical and temperate regions. They are common in intertidal areas, where they use their powerful suction ability to adhere to rocks, algae, and seagrass. They can remain stuck to these surfaces even in powerful currents and when battered by waves. The clingfish used in this study were a species native to the West Coast, and were collected right off San Diego.
By studying the clingfish they collected, Sandoval and colleagues found that the secret mimicking the attachment mechanism that the animal uses was to incorporate a soft layer and slits in the artificial suction cups. The clingfish’s suction disc is lined with rows of hexagonal structures, called papillae, which are covered with microscopic fibers. Researchers mimicked this inside their prototypes with a soft layer made out of silicone. That layer dramatically improved adhesive performance on rough surfaces. The team also incorporated slits into the chamber of the suction cup, which insures better adhesion to irregular, concave surfaces.
“When first speaking with my engineering colleagues, I was sure the trick to optimize the suction cup would come from biology,” said study coauthor Dimitri Deheyn, a researcher in marine biology and biomimicry at the Scripps Institution of Oceanography at UC San Diego. “I also was sure a better suction cup would combine a unique design architecture and a 3D, versatile mechanism of some sort.”
Suction cup performance
The artificial suction discs researchers developed were able to stick to rough surfaces, such as coarse sand papers, and to highly variable surfaces, from rocks to vegetables, both in and out of water. Researchers also showed that their devices could pick up everything from cherries and strawberries without smashing them, to elaborate conch shells and vases.
“Many adhesive devices adhere well only to either a dry or a wet surface and have difficulties with rough surfaces,” said study coauthor Mike Tolley, a robotics expert and professor at the Jacobs School of Engineering at UC San Diego. “Our devices can do it all.”
The devices can hold onto a heavy object for over six hours, which researchers believe could be extended to longer periods of time. In addition, these clingfish-inspired suction discs have an impressive grip given their size: a suction disc can support up to 350 times its own weight while suspended in the air.
The researchers even equipped the arm of a Remotely Operated Vehicle (ROV) with one of their devices and showed it could manipulate a raw egg without breaking it.
“This specific ROV application is of particular interest to me,” said Sandoval, who is a deep sea ROV pilot in addition to being a Ph.D. student. “While piloting ROVs, I use subsea manipulators in order to recover delicate samples from the sea floor. I often wish I had a tool for delicate grip to complement the powerful hold of the metallic jaws of the manipulator. My work in the deep sea was a true motivation behind looking to nature for inspiration for adhesion.”
Experiments and analysis
The clingfish were collected at the tide pools just north of the Ellen Browning Scripps Pier. Part of the Scripps Coastal Marine Reserve, scientists at UC San Diego can acquire licenses to collect organisms for scientific purposes from this area, making it a unique asset for the university.
While building clingfish-inspired suction discs, the team also experimented with mimicking the microscopic fibers of the clingfish by coating the footprint of the artificial suction disc with a layer of microscopic pillars made of silicone. Interestingly, they found that the simpler designs that consisted of just a thick layer of silicone performed better than designs with microscopic pillars.
The interdisciplinary team analyzed the performance of the clingfish-inspired artificial suction discs. The researchers characterized the surface contact of the footprint of the discs to see how they interact with a surface. They sought to understand the underlying energetics by using Finite Element Analysis to model the process of deformation of the suction discs. They also performed tests of adhesive strength on different surface curvatures and different surface roughness, ranging from smooth acrylic to coarse sand paper. They tested the amount of force needed to attach the disc to a surface, depending on surface roughness. They found that very little force was needed to attach the discs to a surface which explains the devices’ ability to handle delicate objects.
abstract Adhesion is difficult to achieve on rough surfaces both in air and underwater. In nature, the northern clingfish (Gobiesox maeandricus) has evolved the impressive ability to adhere onto substrates of various shapes and roughnesses, while subject to strong intertidal surges. The suction disc of the clingfish relies on suction and friction to achieve and maintain adhesion. Inspired by this mechanism of attachment, we designed an artificial suction disc and evaluated its adhesive stress on rough surfaces and non-planar geometries. The artificial suction disc achieved adhesion strengths of 10.1±0.3 kPa in air on surfaces of moderate roughness (grain size, 68 μm), and 14.3±1.5 kPa underwater on coarse surfaces (grain size, 269 μm). By comparison, a commercially available suction cup failed to exhibit any significant adhesion in both scenarios. The roughly 2 g heavy clingfish-inspired suction discs gripped concave surfaces with small radii of curvature (12.5 mm) and supported payloads up to 0.7 kg. We correlated the effect of key bioinspired features (i.e. slits, a soft outer layer, and body geometry) to adhesion performance using contact visualization techniques and Finite Element Analysis. The suction discs were then tested on a Remotely Operated Vehicle (ROV) to demonstrate their utility in the soft manipulation of fragile objects.
capturing bubbles and preventing foam using aerophilic surfaces
leonid rapoport et al. 2020
doi.org/10.1002/admi.201901599
enabling rapid charging lithium metal batteries via surface acoustic wave‐driven electrolyte flow
an huang et al. 2020
doi.org/10.1002/adma.201907516
developed is an integral part of the battery and works by emitting ultrasound waves to create a circulating current in the electrolyte liquid found between the anode and cathode. This prevents the formation of lithium metal growths, called dendrites, during charging that lead to decreased performance and short circuits in LMBs.
The device is made from off-the-shelf smartphone components, which generate sound waves at extremely high frequencies — ranging from 100 million to 10 billion hertz. In phones, these devices are used mainly to filter the wireless cellular signal and identify and filter voice calls and data. Researchers used them instead to generate a flow within the battery’s electrolyte.
“Advances in smartphone technology are truly what allowed us to use ultrasound to improve battery technology,” said James Friend, a professor of mechanical and aerospace engineering at the Jacobs School of Engineering at UC San Diego and the study’s corresponding author.
Currently, LMBs have not been considered a viable option to power everything from electric vehicles to electronics because their lifespan is too short. But these batteries also have twice the capacity of today’s best lithium ion batteries. For example, lithium metal-powered electric vehicles would have twice the range of lithium ion powered vehicles, for the same battery weight.
Researchers showed that a lithium metal battery equipped with the device could be charged and discharged for 250 cycles and a lithium ion battery for more than 2000 cycles. The batteries were charged from zero to 100 percent in 10 minutes for each cycle.
“This work allows for fast-charging and high energy batteries all in one,” said Ping Liu, professor of nanoengineering at the Jacobs School and the paper’s other senior author. “It is exciting and effective.”
The team details their work in the journal Advanced Materials.
Most battery research efforts focus on finding the perfect chemistry to develop batteries that last longer and charge faster, Liu said. By contrast, the UC San Diego team sought to solve a fundamental issue: the fact that in traditional metal batteries, the electrolyte liquid between the cathode and anode is static. As a result, when the battery charges, the lithium ion in the electrolyte is depleted, making it more likely that lithium will deposit unevenly on the anode. This in turn causes the development of needle-like structures called dendrites that can grow unchecked from the anode towards the cathode, causing the battery to short circuit and even catch fire. Rapid charging speeds this phenomenon up.
By propagating ultrasound waves through the battery, the device causes the electrolyte to flow, replenishing the lithium in the electrolyte and making it more likely that the lithium will form uniform, dense deposits on the anode during charging.
The most difficult part of the process was designing the device, said An Huang, the paper’s first author and a Ph.D. student in materials science at UC San Diego. The challenge was working at extremely small scales, understanding the physical phenomena involved and finding an effective way to integrate the device inside the battery.
abstract Both powerful and unstable, practical lithium metal batteries have remained a difficult challenge for over 50 years. With severe ion depletion gradients in the electrolyte during charging, they rapidly develop porosity, dendrites, and dead Li that cause poor performance and, all too often, spectacular failure. Remarkably, incorporating a small, 100 MHz surface acoustic wave device (SAW) solves this problem. Providing acoustic streaming electrolyte flow during charging, the device enables dense Li plating and avoids porosity and dendrites. SAW‐integrated Li cells can operate up to 6 mA cm−2 in a commercial carbonate‐based electrolyte; omitting the SAW leads to short circuiting at 2 mA cm−2. The Li deposition is morphologically dendrite‐free and close to theoretical density when cycling with the SAW. With a 245 µm thick Li anode in a full Li||LFP (LiFePO4) cell, introducing the SAW increases the uncycled Li from 145 to 225 µm, decreasing Li consumption from 41% to only 8%. A closed‐form model is provided to explain the phenomena and serve as a design tool for integrating this chemistry‐agnostic approach into batteries whatever the chemistry within.
exploiting supramolecular interactions from polymeric colloids for strong anisotropic adhesion between solid surfaces
blaise l. tardy et al. 2020
doi.org/10.1002/adma.201906886
Unlike Superglue, the new eco glue develops its full strength in a preferred direction, similar to “Peel and Stick” adhesives. When trying to separate the glued components along the principal plane of the bond, the strength is more than 70 times higher when compared to the direction perpendicular to that plane. All of this means that just a single drop of the “eco” glue has enough strength to hold up to 90kg weight, but can still be easily removed by the touch of a finger, as needed. As Dr Blaise Tardy from the Aalto Department of Bioproducts and Biosystems puts it, ‘The ability to hold this amount of weight with just a few drops is huge, especially from a natural plant-based solution’.
These kind of properties are useful in protecting fragile components in machines that can undergo sudden physical shock such as high-value components in microelectronics, to increase the reusability of valuable structural and decorative elements, in new solutions for packaging applications, and — in general — for the development of greener adhesive solutions.
Producing a comparable product to a market leader at low cost and with new properties
Furthermore, compared to the current approach of making high-strength glues that can involve complex and expensive routes, the team has demonstrated that their solution is just taking biobased particles sources from plants (with a comparatively negligible cost) and just adding water. Since curing time is associated with evaporation of the water phase (~2 hours, currently), it can be controlled, for instance, with heat.
Aalto Professor Orlando Rojas says, ‘Reaching a deep understanding on how the cellulose nanoparticles, mixed with water, to form such an outstanding adhesive is a result of the work between myself, Dr Tardy, Luiz Greca, Professor Hirotaka Ejima, Dr Joseph J. Richardson and Professor Junling Guo and it highlights the fantastic collaboration and integration of knowledge towards the development of an extremely appealing, low-cost and safe application’.
‘Good, green packaging with bad glue still renders the packaging bad’ — Dr Blaise Tardy
Moreover, the prospects for worldwide utilisation (in a 40B€ industry) is quite attractive given the ever-increasing production of cellulose nanocrystals seen across the globe, as supported by incentives in the framework of the circular bioeconomy.
Dr Tardy adds, ‘The truly exciting aspect of this is that although our new adhesive can be sourced directly from residual biomass, such as that from the agro-industry or recycled paper; it outperforms currently available commercial synthetic products by a great many measures’.
abstract Adhesion occurs by covalent bonding, as in reactive structural adhesives, or through noncovalent interactions, which are nearly ubiquitous in nature. A classic example of the latter is gecko feet, where hierarchical features enhance friction across the contact area. Biomimicry of such structured adhesion is regularly achieved by top‐down lithography, which allows for direction‐dependent detachment. However, bottom‐up approaches remain elusive given the scarcity of building blocks that yield strong, cohesive, self‐assembly across multiple length scales. Herein, an exception is introduced, namely, aqueous dispersions of cellulose nanocrystals (CNCs) that form superstructured, adherent layers between solid surfaces upon confined evaporation‐induced self‐assembly (C‐EISA). The inherently strong CNCs (EA > 140 GPa) align into rigid, nematically ordered lamellae across multiple length scales as a result of the stresses associated with confined evaporation. This long‐range order produces remarkable anisotropic adhesive strength when comparing in‐plane (≈7 MPa) and out‐of‐plane (≤0.08 MPa) directions. These adhesive attributes, resulting from self‐assembly, substantially outperform previous biomimetic adhesives obtained by top‐down microfabrication (dry adhesives, friction driven), and represent a unique fluid (aqueous)‐based system with significant anisotropy of adhesion. By using C‐EISA, new emergent properties will be closely tied with the nature of colloids and their hierarchical assemblies.
vertical fibrous morphology and structure-function relationship in natural and biomimetic suction-based adhesion discs
siwei su et al. 2020
doi.org/10.1016/j.matt.2020.01.018
abstract •The lip tissue of remora’s suction disc contains well-aligned collagen fibers
•The structure in natural adhesion disc is remodeled as vertical fibers in matrix
•Electrostatic flocking creates vertical nylon fiber morphology in silicone matrix
•Vertical fibrous morphology is demonstrated to enhance soft adhesion and actuation
Recent years have seen rapid development in bio-inspired materials for adhesion. However, it remains challenging to realize robust adhesion on rough aquatic surfaces. An inspiring natural model is the remora fish, which has evolved to retain powerful adhesion to hosts using a dorsal suction disc. We find that the remora suction disc has a unique fibrous architecture of vertically oriented collagen fibers that enable anisotropic mechanical properties and enhanced adhesion performance. In the engineered prototype, vertically oriented nylon fibers are embedded into the soft silicone matrix using electrostatic flocking. The anisotropic mechanical properties are validated in both natural and biomimetic suction discs. Furthermore, the biomimetic suction disc demonstrates an enhanced adhesion function with a maximum 62.5% increase in pull-off force and a 340% increase in attachment time compared with the silicone control. This work can shed light on natural adhesion mechanisms and inspire novel designs for aquatic soft adhesives and actuators.
The suction disc of the remora — also known as the suckerfish or sharksucker — is so powerful that the fish can even stay attached to leaping dolphins. To understand the underlying mechanism, the researchers looked into the tissue on the soft lip of the suction disc. Between the surface and under-skin layer, they discovered a unique structure: vertically oriented collagen fibers. The fibrous structure provides elasticity for maximizing contact with substrates and decreases the deformation of the lip to maintain its adhesive force. This is the first paper to reveal the detailed morphology structure of the lip disc tissue in remora fish.
“Our research about remoras started with our co-senior author Li Wen’s study on sharks’ skin structure,” said corresponding author Juan Guan of Beihang University. “We were fascinated by the fact that remoras’ suction disc can adhere to surfaces as rough as sharkskin. Sharks swim very fast, yet remoras can hold on to the sharks’ skin very tightly.”
Inspired by the fish, researchers engineered a biomimetic disc infused with vertical nylon fibers with electrostatic flocking, a technique that utilizes an electric charge to align fibers. Compared to pure silicon discs, the biomimetic discs demonstrate an adhesion enhancement of 62.5% and show 3.4 times increment in attachment time. Moreover, the fiber-reinforced biomimetic sucker can hang onto objects that are heavy, irregular, rough, and even under aquatic conditions.
“There are some limitations in controlling the fiber density,” says Guan. “Although nylon and collagen are similar to some extent, we can’t fully mimic their morphological and chemical composition. But we proved a simple concept: by adding vertical fibers to your sucker, you can improve the sucker’s functionality significantly. We’re doing work that can be applied in real life.”
The next step for the team is to improve the current biomimetic sucker by studying and mimicking the structure on the surface skin and under-skin layer. Other improvements include introducing environmentally friendly and biodegradable materials such as silk. The development of vertical fibers could also be applied in soft robotics to achieve intricate movements through controlling deformation.
an ultra-high strength martensitic steel fabricated using selective laser melting additive manufacturing: densification, microstructure, and mechanical properties
raiyan seede et al. 2020
doi.org/10.1016/j.actamat.2019.12.037
"Strong and tough steels have tremendous applications but the strongest ones are usually expensive -- the one exception being martensitic steels that are relatively inexpensive, costing less than a dollar per pound," said Dr. Ibrahim Karaman, Chevron Professor I and head of the Department of Materials Science and Engineering. "We have developed a framework so that 3D printing of these hard steels is possible into any desired geometry and the final object will be virtually defect-free."
Although the procedure developed was initially for martensitic steels, researchers from the Texas A&M said they have made their guidelines general enough so that the same 3D printing pipeline can be used to build intricate objects from other metals and alloys as well.
The findings of the study were reported in the December issue of the journal Acta Materialia.
Steels are made of iron and a small quantity of other elements, including carbon. Martensite steels are formed when steels are heated to extremely high temperatures and then rapidly cooled. The sudden cooling unnaturally confines carbon atoms within iron crystals, giving martensitic steel its signature strength.
To have diverse applications, martensitic steels, particularly a type called low-alloy martensitic steels, need to be assembled into objects of different shapes and sizes depending on a particular application. That's when additive manufacturing, more commonly known as 3D printing, provides a practical solution. Using this technology, complex items can be built layer by layer by heating and melting a single layer of metal powder along a pattern with a sharp laser beam. Each of these layers joined and stacked creates the final 3D-printed object.
However, 3D printing martensitic steels using lasers can introduce unintended defects in the form of pores within the material.
"Porosities are tiny holes that can sharply reduce the strength of the final 3D-printed object, even if the raw material used for the 3D printing is very strong," said Karaman. "To find practical applications for the new martensitic steel, we needed to go back to the drawing board and investigate which laser settings could prevent these defects."
For their experiments, Karaman and the Texas A&M team first chose an existing mathematical model inspired from welding to predict how a single layer of martensitic steel powder would melt for different settings for laser speed and power. By comparing the type and number of defects they observed in a single track of melted powder with the model's predictions, they were able to change their existing framework slightly so that subsequent predictions improved.
After a few such iterations, their framework could correctly forecast, without needing additional experiments, if a new, untested set of laser settings would lead to defects in the martensitic steel. The researchers said this procedure is more time-efficient.
"Testing the entire range of laser setting possibilities to evaluate which ones may lead to defects is extremely time-consuming, and at times, even impractical," said Raiyan Seede, a graduate student in the College of Engineering and the primary author of the study. "By combining experiments and modeling, we were able to develop a simple, quick, step-by-step procedure that can be used to determine which setting would work best for 3D printing of martensitic steels."
Seede also noted that although their guidelines were developed to ensure that martensitic steels can be printed devoid of deformities, their framework can be used to print with any other metal. He said this expanded application is because their framework can be adapted to match the observations from single-track experiments for any given metal.
"Although we started with a focus on 3D printing of martensitic steels, we have since created a more universal printing pipeline," said Karaman. "Also, our guidelines simplify the art of 3D printing metals so that the final product is without porosities, which is an important development for all type of metal additive manufacturing industries that make parts as simple as screws to more complex ones like landing gears, gearboxes or turbines."
abstract Martensitic steels have gained renewed interest recently for their use in automotive, aerospace, and defense applications due to their ultra-high yield strengths and reasonable ductility. A recently discovered low alloy martensitic steel, AF9628, has been shown to exhibit strengths greater than 1.5 GPa with more than 10% tensile ductility, due to the formation of ε-carbide phase. In an effort to produce high strength parts with a high degree of control over geometry, the work herein presents the effects of selective laser melting (SLM) parameters on the microstructure and mechanical properties of this new steel. An optimization framework to determine the process parameters for building porosity-free parts is introduced. This framework utilizes the computationally inexpensive Eagar-Tsai model, calibrated with single track experiments, to predict the melt pool geometry. A geometric criterion for determining maximum allowable hatch spacing is also developed in order to avoid lack of fusion induced porosity in the as-printed parts. Using this framework, fully dense samples were successfully fabricated over a wide range of process parameters, allowing the construction of an SLM processing map for AF9628. The as-printed samples displayed tensile strengths of up to 1.4 GPa, the highest reported to date for any 3D printed alloy, with up to 11% elongation. The demonstrated flexibility in process parameter selection, while maintaining full density, opens up the possibility of local microstructural refinement and parameter optimization for improved mechanical properties in as-printed parts. The process optimization framework introduced here is expected to allow successful printing of new materials in an accelerated fashion.
redox reactions of small organic molecules using ball milling and piezoelectric materials
koji kubota et al. 2019
doi.org/10.1126/science.aay8224
biotechnological mass production of dna origami
florian praetorius et al. 2017
doi.org/10.1038/nature24650
directing the outcome of co2 reduction at bismuth cathodes using varied ionic liquid promoters
abderrahman atifi et al. 2018
doi.org/10.1021/acscatal.7b03433
observation of giant conductance fluctuations in a protein
stuart lindsay et al. 2017
doi.org/10.1088/2399-1984/aa8f91
room-temperature operation of low-voltage, non-volatile, compound-semiconductor memory cells
ofogh tizno et al. 2019
doi.org/10.1038/s41598-019-45370-1
large-scale generation of functional mrna-encapsulating exosomes via cellular nanoporation
zhaogang yang et al. 2019
doi.org/10.1038/s41551-019-0485-1
The scientists placed about 1 million donated cells (such as mesenchymal cells collected from human fat) on a nano-engineered silicon wafer and used an electrical stimulus to inject synthetic DNA into the donor cells. As a result of this DNA force-feeding, as Lee described it, the cells need to eject unwanted material as part of DNA transcribed messenger RNA and repair holes that have been poked in their membranes.
“They kill two birds with one stone: They fix the leakage to the cell membrane and dump the garbage out,” Lee said. “The garbage bag they throw out is the exosome. What’s expelled from the cell is our drug.”
The electrical stimulation had a bonus effect of a thousand-fold increase of therapeutic genes in a large number of exosomes released by the cells, a sign that the technology is scalable to produce enough nanoparticles for use in humans.
Essential to any gene therapy, of course, is knowing what genes need to be delivered to fix a medical problem. For this work, the researchers chose to test the results on glioma brain tumors by delivering a gene called PTEN, a cancer-suppressor gene. Mutations of PTEN that turn off that suppression role can allow cancer cells to grow unchecked.
For Lee, founder of Ohio State’s Center for Affordable Nanoengineering of Polymeric Biomedical Devices, producing the gene is the easy part. The synthetic DNA force-fed to donor cells is copied into a new molecule consisting of messenger RNA, which contains the instructions needed to produce a specific protein. Each exosome bubble containing messenger RNA is transformed into a nanoparticle ready for transport, with no blood-brain barrier to worry about.
“The advantage of this is there is no toxicity, nothing to provoke an immune response,” said Lee, also a member of Ohio State’s Comprehensive Cancer Center. “Exosomes go almost everywhere in the body, including passing the blood-brain barrier. Most drugs can’t go to the brain.
“We don’t want the exosomes to go to the wrong place. They’re programmed not only to kill cancer cells, but to know where to go to find the cancer cells. You don’t want to kill the good guys.”
The testing in mice showed the labeled exosomes were far more likely to travel to the brain tumors and slow their growth compared to substances used as controls.
Because of exosomes’ safe access to the brain, Lee said, this drug-delivery system has promise for future applications in neurological diseases such as Alzheimer’s and Parkinson’s disease.
“Hopefully, one day this can be used for medical needs,” Lee said. “We’ve provided the method. If somebody knows what kind of gene combination can cure a certain disease but they need a therapy, here it is.”
abstract Exosomes are attractive as nucleic-acid carriers because of their favourable pharmacokinetic and immunological properties and their ability to penetrate physiological barriers that are impermeable to synthetic drug-delivery vehicles. However, inserting exogenous nucleic acids, especially large messenger RNAs, into cell-secreted exosomes leads to low yields. Here we report a cellular-nanoporation method for the production of large quantities of exosomes containing therapeutic mRNAs and targeting peptides. We transfected various source cells with plasmid DNAs and stimulated the cells with a focal and transient electrical stimulus that promotes the release of exosomes carrying transcribed mRNAs and targeting peptides. Compared with bulk electroporation and other exosome-production strategies, cellular nanoporation produced up to 50-fold more exosomes and a more than 103-fold increase in exosomal mRNA transcripts, even from cells with low basal levels of exosome secretion. In orthotopic phosphatase and tensin homologue (PTEN)-deficient glioma mouse models, mRNA-containing exosomes restored tumour-suppressor function, enhanced inhibition of tumour growth and increased survival. Cellular nanoporation may enable the use of exosomes as a universal nucleic-acid carrier for applications requiring transcriptional manipulation.
plant gene editing through de novo induction of meristems
michael f. maher et al. 2019
doi.org/10.1038/s41587-019-0337-2
Despite dramatic advances in scientists’ ability to edit plant genomes using gene-editing tools such as CRISPR and TALENs, researchers were stuck using an antiquated approach — tissue culture. It has been in use for decades and is costly, labor intensive and requires precise work in a sterile environment. Researchers use tissue culture to deliver genes and gene editing reagents, or chemicals that drive the reaction, to plants.
“A handful of years ago the National Academy of Sciences convened a meeting of plant scientists, calling on the community to solve the tissue culture bottleneck and help realize the potential of gene editing in plants,” said Dan Voytas, professor in Genetics, Cell Biology and Development in the College of Biological Sciences and senior author on the paper. “We have advanced genome editing technology but we needed a novel way to efficiently deliver gene editing reagents to plants. The methods in this paper present a whole new way of doing business.”
The new methods will:
• drastically reduce the time needed to edit plant genes from as long as nine months to as short as a few weeks;
• work in more plant species than was possible using tissue culture, which is limited to specific species and varieties;
• allow researchers to produce genetically edited plants without the need of a sterile lab, making it a viable approach for small labs and companies to utilize.
To eliminate the arduous work that goes into gene-editing through tissue culture, co-first authors Ryan Nasti and Michael Maher developed new methods that leverage important plant growth regulators responsible for plant development.
Using growth regulators and gene editing reagents, researchers trigger seedlings to develop new shoots that contain edited genes. Researchers collect seeds from these gene-edited shoots and continue experiments. No cell cultures needed.
The approaches differ in how the growth regulators are applied and at what scale. The approach developed by Nasti allows small-scale rapid testing — with results in weeks instead of months or years — of different combinations of growth regulators. “This approach allows for rapid testing so that researchers can optimize combinations of growth regulators and increase their efficacy,” he said.
Maher used the same basic principles to make the process more accessible by eliminating the need for a sterile lab environment. “With this method, you don’t need sterile technique. You could do this in your garage,” he said. He added that this technique opens up the possibility that smaller research groups with less resources can gene edit plants and test how well they do.
“Nasti and Maher have democratized plant gene editing. It will no longer take months in a sterile lab with dozens of people in tissue culture hoods,” Voytas said.
The researchers used a tobacco species as their model, but have already demonstrated the method works in grape, tomato and potato plants. They believe the findings will likely transfer across many species. Plant geneticists and agricultural biotechnologists aim to ensure stable food sources for a growing global population in a warming climate, where pest outbreaks and extreme weather events are commonplace. These new methods will allow them to work more efficiently.
abstract Plant gene editing is typically performed by delivering reagents such as Cas9 and single guide RNAs to explants in culture. Edited cells are then induced to differentiate into whole plants by exposure to various hormones. The creation of edited plants through tissue culture is often inefficient, time-consuming, works for only limited species and genotypes, and causes unintended changes to the genome and epigenome. Here we report two methods to generate gene-edited dicotyledonous plants through de novo meristem induction. Developmental regulators and gene-editing reagents are delivered to somatic cells of whole plants. This induces meristems that produce shoots with targeted DNA modifications, and gene edits are transmitted to the next generation. The de novo induction of gene-edited meristems sidesteps the need for tissue culture and promises to overcome a bottleneck in plant gene editing.
the protein tyrosine phosphatase 1b inhibitor msi-1436 stimulates regeneration of heart and multiple other tissues
ashley m. smith et al. 2017
doi.org/10.1038/s41536-017-0008-1
biomimetic tooth repair: amelogenin-derived peptide enables in vitro remineralization of human enamel
sami dogan et al. 2018
https://doi.org/10.1021/acsbiomaterials.7b00959
thermoresponsive gel embedded with adipose stem-cell-derived extracellular vesicles promotes esophageal fistula healing in a thermo-actuated delivery strategy
amanda k. a. silva et al. 2018
doi.org/10.1021/acsnano.8b00117
repair of critical sized cranial defects with bmp9-transduced calvarial cells delivered in a thermoresponsive scaffold
zari p. dumanian et al. 2017
doi.org/10.1371/journal.pone.0172327
extreme anoxia tolerance in crucian carp and goldfish through neofunctionalization of duplicated genes creating a new ethanol-producing pyruvate decarboxylase pathway
cathrine e. fagernes et al. 2017
doi.org/10.1038/s41598-017-07385-4
forceful manipulation with micro air vehicles
matthew a. estrada et al. 2018
doi.org/10.1126/scirobotics.aau6903
polymagnet
directional magnets
polymagnet.com
transparent “wood”
delignified polymer
optically transparent wood from a nanoporous cellulosic template: combining functional and structural performance
li et al 2016
http://doi.org/10.1021/acs.biomac.6b00145
Link: doi.org/10.1021/acs.biomac.6b00145
highly anisotropic, highly transparent wood composites
zhu et al 2016
http://doi.org/10.1002/adma.201600427
Link: doi.org/10.1002/adma.201600427
hempcrete
lime and hemp shiv
accurate genomic prediction of human height
louis lello et al. 2018
doi.org/10.1534/genetics.118.301267
engineering a highly elastic human protein–based sealant for surgical applications
nasim annabi et al. 2017
doi.org/10.1126/scitranslmed.aai7466
bioinspired functional gradients for toughness augmentation in synthetic polymer systems
kayetan chorazewicz et al. 2018
doi.org/10.1002/macp.201800134
creating nanoscale emulsions using condensation
ingrid f. guha et al. 2017
doi.org/10.1038/s41467-017-01420-8
carbothermal shock synthesis of high-entropy-alloy nanoparticles
yonggang yao et al. 2018
doi.org/10.1126/science.aan5412
origami, kirigami
rational design of reconfigurable prismatic architected materials
overvelde et al. 2017
doi.org/10.1038/nature20824
geometric mechanics of origami patterns exhibiting poisson’s ratio switch by breaking mountain/valley assignment
phanisri p. pratapa et al. 2019
doi.org/10.1103/physrevlett.122.155501
new type of origami that can morph from one pattern into a different one, or even a hybrid of two patterns, instantly altering many of its structural characteristics.
The research, which was supported by the National Science Foundation and is to be published April 19 in the journal Physical Review Letters, could unlock new types of origami-based structures or metamaterials that leverage the characteristics of two types of origami.
“This hybrid origami allows for reprogrammable mechanical properties and the ability to change those properties while the material is in service,” said Glaucio Paulino, a professor in the Georgia Tech School of Civil and Environmental Engineering.
The researchers started with two types of origami patterns: the Miura-ori and the eggbox, both of which can be formed into sheets of repeating patterns. The Miura-ori looks like rows of folded zig-zags, while the eggbox pattern resembles a mountain range with repeating peaks and valleys.
Both are capable of being compressed into a very small space, but when expanded they behave differently from one another in how they respond to bending. The eggbox pattern resembles a dome when bent, and the Miura-ori takes the shape of a saddle.
“Traditionally, if you have an eggbox pattern, you are locked into the characteristics of that particular pattern,” said Paulino, who is also the Raymond Allen Jones Chair of Engineering in the School of Civil and Environmental Engineering. “With this new pattern, which we are calling morph, that’s no longer the case.”
The new origami pattern achieves its morphing ability by a redesign of the geometry of two of the four planes that comprise one section of the origami. By shrinking those two planes on one side, it enables their creases to shift from a mountain to a valley, or in other words, to fold in the opposite direction.
And importantly, the transition from peak to valley can occur whether the origami is formed from a flexible material such as paper or a rigid material such as metal.
That means, for example, that origami-based structures used for acoustic systems — which already are capable of expanding and contracting to increase or decrease the volume of the sound response — could go one step further, changing how they bend to potentially offer an even greater range of resonant responses. In the example of the drone crash protection system, the new origami pattern could potentially offer other customization options or alter aspects of its impact resistance, Paulino said.
“NSF’s investments in fundamental research of architected materials has pushed the frontiers and created ‘shape-shifting’ structures for applications in space exploration, robotics and medicine,” said Robert B. Stone, NSF’s Civil, Mechanical and Manufacturing Innovation division director.
The new origami pattern is also capable of taking on a hybrid structure, where certain rows are folded into one configuration and others were folded in the other. In such a configuration, the structure would exhibit characteristics of both types.
“There are a large number of combinations in terms of how these could be configured, which offers a lot of customization possibilities for structures based on the morph pattern,” said Ke Liu, a former graduate student at Georgia Tech and now a postdoctoral scholar at the California Institute of Technology.
Another unique characteristic of the morph pattern is what happens when a Miura-ori row is situated between two eggbox rows. Typically, when tension is applied to pull apart either of the patterns, they respond by giving in and flattening their shape. However, in this new instance, the Miura-ori pattern locks into place.
“The locking is very strong, and there is no way to break that hold other than to tear the entire structure apart,” said Phanisri Pratapa, a former postdoctoral fellow at Georgia Tech and now an assistant professor of civil engineering at the Indian Institute of Technology Madras.
The locking could enable structures to limit the amount of expansion possible and change that limit on the fly, Pratapa said.
abstract Exploring the configurational space of specific origami patterns [e.g., Miura-ori (flat surface with parallelogram crease patterns), eggbox] has led to notable advances in science and technology. To augment the origami design space, we present a pattern, named “Morph,” which combines the features of its parent patterns. We introduce a four-vertex origami cell that morphs continuously between a Miura mode and an eggbox mode, forming an homotopy class of configurations. This is achieved by changing the mountain and valley assignment of one of the creases, leading to a smooth switch through a wide range of negative and positive Poisson’s ratios. We present elegant analytical expressions of Poisson’s ratios for both in-plane stretching and out-of-plane bending and find that they are equal in magnitude and opposite in sign. Further, we show that by combining compatible unit cells in each of the aforementioned modes through kinematic bifurcation, we can create hybrid origami patterns that display unique properties, such as topological mode locking and tunable switching of Poisson’s ratio.
nature-inspired, 3d origami solar steam generator toward near full utilization of solar energy
seunghyun hong et al. 2018
doi.org/10.1021/acsami.8b07150
kirigami-inspired nanoconfined polymer conducting nanosheets with 2000% stretchability
ying-shi guan et al. 2018
doi.org/10.1002/adma.201706390
kirigami–style slits in stretchy films
news.mit.edu/2018/paper-folding-art-inspires-better-bandages-0327
flexible and stretchable medical devices
kuniharu takei 2018 to read next
origami-based impact mitigation via rarefaction solitary wave creation
hiromi yasuda et al. 2019
doi.org/10.1126/sciadv.aau2835
a paper model of a metamaterial that uses "folding creases" to soften impact forces and instead promote forces that relax stresses in the chain. The team published its results May 24 in Science Advances.
"If you were wearing a football helmet made of this material and something hit the helmet, you'd never feel that hit on your head. By the time the energy reaches you, it's no longer pushing. It's pulling," said corresponding author Jinkyu Yang, a UW associate professor of aeronautics and astronautics.
Yang and his team designed this new metamaterial to have the properties they wanted.
"Metamaterials are like Legos. You can make all types of structures by repeating a single type of building block, or unit cell as we call it," he said. "Depending on how you design your unit cell, you can create a material with unique mechanical properties that are unprecedented in nature."
The researchers turned to the art of origami to create this particular unit cell.
"Origami is great for realizing the unit cell," said co-author Yasuhiro Miyazawa, a UW aeronautics and astronautics doctoral student. "By changing where we introduce creases into flat materials, we can design materials that exhibit different degrees of stiffness when they fold and unfold. Here we've created a unit cell that softens the force it feels when someone pushes on it, and it accentuates the tension that follows as the cell returns to its normal shape."
Just like origami, these unit cell prototypes are made out of paper. The researchers used a laser cutter to cut dotted lines into paper to designate where to fold. The team folded the paper along the lines to form a cylindrical structure, and then glued acrylic caps on either end to connect the cells into a long chain.
The researchers lined up 20 cells and connected one end to a device that pushed and set off a reaction throughout the chain. Using six GoPro cameras, the team tracked the initial compression wave and the following tension wave as the unit cells returned to normal.
The chain composed of the origami cells showed the counterintuitive wave motion: Even though the compressive pushing force from the device started the whole reaction, that force never made it to the other end of the chain. Instead, it was replaced by the tension force that started as the first unit cells returned to normal and propagated faster and faster down the chain. So the unit cells at the end of the chain only felt the tension force pulling them back.
"Impact is a problem we encounter on a daily basis, and our system provides a completely new approach to reducing its effects. For example, we'd like to use it to help both people and cars fare better in car accidents," Yang said. "Right now it's made out of paper, but we plan to make it out of a composite material. Ideally, we could optimize the material for each specific application."
abstract The principles underlying the art of origami paper folding can be applied to design sophisticated metamaterials with unique mechanical properties. By exploiting the flat crease patterns that determine the dynamic folding and unfolding motion of origami, we are able to design an origami-based metamaterial that can form rarefaction solitary waves. Our analytical, numerical, and experimental results demonstrate that this rarefaction solitary wave overtakes initial compressive strain waves, thereby causing the latter part of the origami structure to feel tension first instead of compression under impact. This counterintuitive dynamic mechanism can be used to create a highly efficient—yet reusable—impact mitigating system without relying on material damping, plasticity, or fracture.
transport
using the jet stream for sustainable airship and balloon transportation of cargo and hydrogen
julian david hunt et al. 2019
doi.org/10.1016/j.ecmx.2019.100016
Airships were introduced in the first half of the 20th century before conventional aircraft were used for the long-range transport of cargo and passengers. Their use in cargo and passenger transport was however quickly discontinued for a number of reasons, including the risk of a hydrogen explosion -- for which the Hindenburg disaster of 1937 served as a stark case in point; their lower speed compared to that of airplanes; and the lack of reliable weather forecasts. Since then, considerable advances in material sciences, our ability to forecast the weather, and the urgent need to reduce energy consumption and CO2 emissions, have steadily been bringing airships back into political, business, and scientific conversations as a possible transportation alternative.
The transport sector is responsible for around 25% of global CO2 emissions caused by humans. Of these emissions, 3% come from cargo ships, but this figure is expected to increase by between 50% and 250% until 2050. These projections necessitate finding new approaches to transporting cargo with a lower demand for energy and lower CO2 emissions. In their study published in the Springer journal Energy Conversion and Management, researchers from IIASA, Brazil, Germany, and Malaysia looked into how an airship-based industry could be developed using the jet stream as the energy medium to transport cargo around the world.
The jet stream is a core of strong winds that flows from west to east, around 8 to 12 kilometers above the Earth's surface. According to the researchers, airships flying in the jet stream could reduce CO2 emissions and fuel consumption, as the jet stream itself would contribute most of the energy required to move the airship between destinations, resulting in a round trip of 16 days in the northern hemisphere, and 14 days in the southern hemisphere. This is considerably less time compared to current maritime shipping routes, particularly in the southern hemisphere.
The researchers postulate that the reintroduction of airships into the transport sector could also offer an alternative for the transport of hydrogen. Hydrogen is a good energy carrier and a valuable energy storage alternative. Given that renewable electricity, for example, excess wind power, can be transformed into hydrogen, there is optimism that the hydrogen economy will form a fundamental part of a clean and sustainable future. One of the challenges to implementing a hydrogen-based economy is cooling the hydrogen to below -253°C to liquefy it. The process consumes almost 30% of the embodied energy, with further energy of around 3% required to transport the liquefied hydrogen. In their study, the authors however propose that instead of using energy in liquefaction, hydrogen in gaseous form could be carried inside the airship or balloon and transported by the jet stream with a lower fuel requirement. Once the airship or balloon reaches its destination, the cargo can be unloaded removing around 60% or 80% of the hydrogen used for lift, and leaving 40% or 20%, of the hydrogen inside the airship or balloon to provide enough buoyancy for the return trip without cargo. To address the risk of combustion of the hydrogen in the airship, the authors suggest automating the operation, loading, and unloading of hydrogen airships and designing flightpaths that avoid cities to reduce the risk of fatalities in the event of an accident.
According to study lead-author Julian Hunt, an IIASA post-doctoral fellow, a further interesting aspect unveiled in this study is the possibility that airships and balloons can also be used to improve the efficiency of liquefying hydrogen. As the temperature of the stratosphere (where the airships will be flying to utilize the jet stream) varies between -50°C to -80°C, it means that less energy will be required to meet the -253°C mark if the process happens onboard the airship. The energy required for the additional cooling needed can be generated using the hydrogen in the airship.
Hunt says that this process also presents a number of additional possibilities: The process of generating energy from hydrogen produces water -- one ton of hydrogen produces nine tons of water. This water could be used to increase the weight of the airship and further save energy in its descending trajectory. Another possible application for the water produced is rainmaking, which involves releasing the water produced from the stratosphere at a height where it will freeze before entering the troposphere where it would then melt again. This reduces the temperature and increases the relative humidity of the troposphere until it saturates and starts raining. The rain will in turn initiate a convection rain pattern, thus feeding even more humidity and rain into the system. This process could be used to alleviate water stress in regions suffering from shortages.
"Airships have been used in the past and provided great services to society. Due to current needs, airships should be reconsidered and returned to the skies. Our paper presents results and arguments in favor of this. The development of an airship industry will reduce the costs of fast delivery cargo shipping, particularly in regions far from the coast. The possibility to transport hydrogen without the need to liquefy it would reduce the costs for the development of a sustainable and hydrogen based economy, ultimately increasing the feasibility of a 100% renewable world," concludes Hunt.
abstract •Airships can use the jet stream for efficient cargo or hydrogen transportation.
•Around the world routes in the northern and southern hemisphere take 16 and 14 days.
•A 10-fold increase in airship dimensions increases 1000 fold its useful lift.
•Transposing hydrogen or cargo increases the flexibility of this alternative.
The maritime shipping sector is a major contributor to CO2 emissions and this figure is expected to rise in coming decades. With the intent of reducing emissions from this sector, this research proposes the utilization of the jet stream to transport a combination of cargo and hydrogen, using airships or balloons at altitudes of 10–20 km. The jet streams flow in the mid-latitudes predominantly in a west–east direction, reaching an average wind speed of 165 km/h. Using this combination of high wind speeds and reliable direction, hydrogen-filled airships or balloons could carry hydrogen with a lower fuel requirement and shorter travel time compared to conventional shipping. Jet streams at different altitudes in the atmosphere were used to identify the most appropriate circular routes for global airship travel. Round-the-world trips would take 16 days in the Northern Hemisphere and 14 in the Southern Hemisphere. Hydrogen transport via the jet stream, due to its lower energy consumption and shorter cargo delivery time, access to cities far from the coast, could be a competitive alternative to maritime shipping and liquefied hydrogen tankers in the development of a sustainable future hydrogen economy.
radiation
remote detection of radioactive material using mid-ir laser–driven electron avalanche
robert m. schwartz et al. 2019
doi.org/10.1126/sciadv.aav6804
"Traditional detection methods rely on a radioactive decay particle interacting directly with a detector. All of these methods decline in sensitivity with distance," said Robert Schwartz, a physics graduate student at UMD and the lead author of the research paper. "The benefit of our method is that it is inherently a remote process. With further development, it could detect radioactive material inside a box from the length of a football field."
As radioactive material emits decay particles, the particles strip electrons from -- or ionize -- nearby atoms in the air, creating a small number of free electrons that quickly attach to oxygen molecules. By focusing an infrared laser beam into this area, Schwartz and his colleagues easily detached these electrons from their oxygen molecules, seeding an avalanche-like rapid increase in free electrons that is relatively easy to detect.
"An electron avalanche can start with a single seed electron. Because the air near a radioactive source has some charged oxygen molecules -- even outside a shielded container -- it provides an opportunity to seed an avalanche by applying an intense laser field," said Howard Milchberg, a professor of physics and electrical and computer engineering at UMD and senior author of the research paper, who also has an appointment at IREAP. "Electron avalanches were among the first demonstrations after the laser was invented. This is not a new phenomenon, but we are the first to use an infrared laser to seed an avalanche breakdown for radiation detection. The laser's infrared wavelength is important, because it can easily and specifically detach electrons from oxygen ions."
Applying an intense, infrared laser field causes the free electrons caught in the beam to oscillate and collide with atoms nearby. When these collisions become energetic enough, they can rip more electrons away from the atoms.
"A simple view of avalanche is that after one collision, you have two electrons. Then, this happens again and you have four. Then the whole thing cascades until you have full ionization, where all atoms in the system have at least one electron removed," Milchberg explained.
As the air in the laser's path begins to ionize, it has a measurable effect on the infrared light reflected, or backscattered, toward a detector. By tracking these changes, Schwartz, Milchberg and their colleagues were able to determine when the air began to ionize and how long it took to reach full ionization.
The timing of the ionization process, or the electron avalanche breakdown, gives the researchers an indication of how many seed electrons were available to begin the avalanche. This estimate, in turn, can indicate how much radioactive material is present in the target.
"Timing of ionization is one of the most sensitive ways to detect initial electron density," said Daniel Woodbury, a physics graduate student at UMD and a co-author of the research paper. "We're using a relatively weak probe laser pulse, but it's 'chirped,' meaning that shorter wavelengths pass though the avalanching air first, then longer ones. By measuring the spectral components of the infrared light that passes through versus what is reflected, we can determine when ionization starts and reaches its endpoint."
The researchers note that their method is highly specific and sensitive to the detection of radioactive material. Without a laser pulse, radioactive material alone will not induce an electron avalanche. Similarly, a laser pulse alone will not induce an avalanche, without the seed electrons created by the radioactive material.
While the method remains a proof-of-concept exercise for now, the researchers envision further engineering developments that they hope will enable practical applications to enhance security at ports of entry across the globe.
"Right now we're working with a lab-sized laser, but in 10 years or so, engineers may be able to fit a system like this inside a van," Schwartz said. "Anywhere you can park a truck, you can deploy such a system. This would provide a very powerful tool to monitor activity at ports."
bioinspired mechanical device generates plasma in water via cavitation
xin tang, david staack 2019
doi.org/10.1126/sciadv.aau7765
3D printing technology to replicate not only the physical shape of a snapping shrimp's claw, but also the complex mechanism through which it generates plasma.
The team's research was published March 15 in the online journal Science Advances.
"Generally, when you look to nature, evolutionary pressure makes it so that nature is very efficient at doing things," Staack said. "I find it interesting that the shrimp has been doing intense shock waves, plasma chemistry and nanoparticle synthesis for millions of years."
When the snapping shrimp -- also known as the pistol shrimp -- snaps its claw, it shoots out a jet of water fast enough to generate a bubble which, when it collapses, creates a loud noise and emits light. The high pressures and temperatures produced in this process lead to plasma formation.
The project, led by Staack, began more than four years ago as an offshoot of a National Science Foundation (NSF)-funded project on electrical discharge plasma in liquids. In comparing the plasma-generation process of the snapping shrimp to their electrical plasma process, the researchers became curious if they could find a way to measure and replicate its properties.
The researchers set out to mimic the mechanics of the snapping shrimp's claw with initial support from the NSF, carefully studying how the sea creature creates a cavitation bubble that generates plasma at upwards of 3,000 degrees Fahrenheit.
"In our paper, we report the first direct imaging of the light emission induced by the same method the shrimp uses: the mechanically generated energy focusing on a collapsingcavitation and the following shockwave propagation," Staack said. "The bio-inspired mechanical design allowed us to carry out repetitive and consistent experiments on the plasma generation and indicate a significant increase in conversion efficiency compared to sonic, laser and electric induced cavitation."
Staack said the use of 3D printing was instrumental in the progression of this project, allowing the researchers to create an accurate, scaled-up model of the snapping shrimp's claw in a way that was impossible just a few years ago.
Previous attempts at replicating the shrimp's behavior focused on the two-dimensional geometry of the shrimp, ultimately missing some of the complex 3D processes that newer technology allowed the researchers to recreate the mechanism successfully.
Staack and Tang created a 3D model of a snapping shrimp's molted claw husk five-times larger than it appears in nature. To power the mechanism without the aid of the shrimp's muscles, the researchers implemented a mousetrap-like spring system.
In nature, shrimp use the cavitation bubble as a weapon to generate shocks and stun their prey. A scaled-up version of the shrimp's mechanism could be used for a broad range of disciplines including analytical chemistry, physics and material processing.
"Shrimp use the systems as a weapon and that is certainly one application," Staack said. "The pressure and shocks can stun small fish or break-up a kidney stone. The cavitation and dynamics can be used to modify boundary layer flow and reduce drag for a boat. Other applications take advantage of the chemistry of the plasma state. Nanoparticles can be synthesized with exotic phases due to the extreme conditions during synthesis. Water can be sterilized. Oil can be upgraded."
Drawing inspiration from the snapping shrimp's plasma and shockwave capabilities, Staack is working with a team of colleagues from the mechanical engineering department on a spin-off project to advance the drilling technology used to create geothermal wells that tap into the Earth's natural heat. By enabling electrodes on the tip of a drill bit to emit a microscopic plasma discharge, the technology will help break through hard rock and streamline the drilling process.
Moving forward, Staack said some of the goals for future research include determining the temperature of the plasma generated, finding out how large they can scale up the mechanism and testing some potential applications.
They are also working on refining the most efficient version of the mechanism, removing parts from the claw model that do not serve a purpose in the creation of plasma.
"What we've learned from this is that we don't need all of this shrimp biology," Staack said. "We need the little back plunger and we need the channel, but we don't need the part that the shrimp uses to hit with. There are some things which evolved for different reasons. Some of the things we're doing now are figuring out what the distilled version of this mechanism is."
abstract Nature can generate plasma in liquids more efficiently than human-designed devices using electricity, acoustics, or light. In the animal world, snapping shrimp can induce cavitation that collapses to produce high pressures and temperatures, leading to efficient plasma formation with photon and shock wave emission via energy focusing. Here, we report a bioinspired mechanical device that mimics the plasma generation technique of the snapping shrimp. This device was manufactured using additive manufacturing based on micro–x-ray computed tomography of a snapping shrimp claw molt. A spring fixture was designed to reliably actuate the claw with appropriate force and velocity to produce a high-speed water jet that matches the cavitation number and Reynolds number of the shrimp. Light emission and shocks were imaged, which indicate that our device reproduces the shrimp’s plasma generation technique and is more efficient than other plasma generation methods.
the macaque anterior cingulate cortex translates counterfactual choice value into actual behavioral change
elsa f. fouragnan et al. 2019
doi.org/10.1038/s41593-019-0375-6
low–intensity ultrasound affecting the brain
counterfactual thinking is causally related to a frontal part of the brain, called the anterior cingulate cortex. And scientists have proven that the process can be changed by targeting neurons (nerve cells) in this region using low-intensity ultrasound.
The study was led by Dr Elsa Fouragnan at the University of Plymouth and published Monday 15 April in Nature Neuroscience.
Counterfactual thinking is an important cognitive process by which humans and animals make decisions -- not only based on what they are currently experiencing, but by comparing their present experience with potential alternatives. In typical circumstances, should these alternatives become available in the near future, one would adaptively switch to them. For example, if the sun was shining while working, one would go out and enjoy the sun as soon as work is done.
If neurons in the anterior cingulate cortex are not working properly, then it would not be possible to switch to alternative options, even when these alternatives are the best available. Scientists believe that this is what happens in some psychiatric conditions where people are stuck in dysfunctional habits.
The study showed for the first time how low-intensity ultrasonic waves can be used to non-invasively, and with pinpoint accuracy, modulate normal brain function -- affecting counterfactual thinking and the ability to switch to better alternative.
The research, conducted in macaques monkeys, follows previous work highlighting the safeness of the non-invasive ultrasound technique and its effect on the brain.
In the study, the macaques were tasked with finding a treat from a variety of options. They quickly learned which one was best, but the 'best' option was not always available to choose. Thus, they had to keep it in mind for when it became available again.
After showing that the cingulate cortex was linked with remembering which option was best, researchers used low intensity ultrasound to modulate the activity in this brain region and see its effect on behaviours. When the neurons were stimulated, their counterfactual thinking was impaired.
Dr Fouragnan explained why the findings were so significant and what it could mean for future treatment: "This is a really exciting study for two main reasons -- firstly because we discovered that the cingulate cortex is crucial to help switch to better alternatives, and secondly because low-intensity ultrasound can be used to reversibly change brain activity in very precise part of the brain," she said.
Ultrasound is well known as an imaging tool -- in pregnancy, for example -- but it can also be used as a therapeutic method, particularly for safely modulating brain activity. This is possible because the mechanical vibrations caused by ultrasonic waves can cause the generation or suppression of electrical signals in the brain, which in turn can be used to restore normal brain function.
Dr Fouragnan continued: "Ultrasound neurostimulation is an early-stage, non-invasive therapeutic technology that has the potential to improve the lives of millions of patients with mental health conditions by stimulating brain tissues with millimetre accuracy. Presently, neuromodulation techniques do exist for humans, to help people with conditions such as major depression or Parkinson's. But there are no techniques that have this level of accuracy while remaining non-invasive.
…
abstract The neural mechanisms mediating sensory-guided decision-making have received considerable attention, but animals often pursue behaviors for which there is currently no sensory evidence. Such behaviors are guided by internal representations of choice values that have to be maintained even when these choices are unavailable. We investigated how four macaque monkeys maintained representations of the value of counterfactual choices—choices that could not be taken at the current moment but which could be taken in the future. Using functional magnetic resonance imaging, we found two different patterns of activity co-varying with values of counterfactual choices in a circuit spanning the hippocampus, the anterior lateral prefrontal cortex and the anterior cingulate cortex. Anterior cingulate cortex activity also reflected whether the internal value representations would be translated into actual behavioral change. To establish the causal importance of the anterior cingulate cortex for this translation process, we used a novel technique, transcranial focused ultrasound stimulation, to reversibly disrupt anterior cingulate cortex activity.
spine backpacks
vertepac.com/store/
kardiaband
alivecor-uk.myshopify.com/
temperature and humidity based projections of a rapid rise in global heat stress exposure during the 21st century
ethan david coffel et al. 2017
doi.org/10.1088/1748-9326/aaa00e
sonic weapons
“sonic weapons”
theguardian.com/world/2017/sep/14/mystery-of-sonic-weapon-attacks-at-us-embassy-in-cuba-deepens
microwave weapons are prime suspect in ills of u.s. embassy workers
william j. broad 2018
nytimes.com/2018/09/01/science/sonic-attack-cuba-microwave.html
the mysterious “sonic attacks” in cuba might have actually been caused by zika pesticides
dan vergano 2019 et al. 2019
buzzfeednews.com/article/danvergano/cuban-diplomats-sonic-attacks-zika-virus
a robust data-driven approach identifies four personality types across four large data sets
martin gerlach et al. 2018
doi.org/10.1038/s41562-018-0419-z
revolutionary wealth
alvin toffler 2006
solar electricity handbook: a simple, practical guide to solar energy, designing and installing solar photovoltaic systems
michael boxwell 2017
wtf
robert peston 2017 9781473661295 unread
how to let go of the world and love all the things climate can’t change
josh fox 2016
howtoletgomovie.com
soek.pro/how-to-let-go/news-815125/
the fall of the american empire—and then what?
johan galtung 2009 unread
stoic antifragilistas, optimise business as usual
rightwing deniers, business as usual
anarchist collapsniks, the end is nigh
leftwing environmentalists, drastic interventionists
combined effects: collapse, intervention, optimised business as usual