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Adding water to solids can make them stronger, providing engineers with exciting new material composites

Adding water to solids can make them stronger, providing engineers with exciting new material composites | Amazing Science | Scoop.it

Contrary to intuition, adding pockets of water to solids can actually make them stronger. This finding, the result of research by Yale scientists, offers “a new knob to turn” for engineers, the researchers say. Engineers will be able to add exciting new properties to composite materials–such as electromagnetism–by embedding droplets of liquid, and, on a purely scientific level, the research provides valuable insight into the nature of the material properties at small and large scales–how the relative strengths of a material at one size can be opposite to that at another size.


“This is a great example of how different types of physics emerge at different scales,” Dr. Eric Dufresne, associate professor of mechanical engineering and materials science at Yale and principle investigator of the study, told The Speaker. “Shrinking the scale of an object can really change how it behaves.”


“Surface tension is a force that tries to reduce the surface area of a material,” Dufresne told us. “It is familiar in fluids–it’s the force that pulls water into a sponge, makes wet hair clump together and lets insects walk on water. Solids have surface tension too, but usually the ‘elastic force’ of the solid is so strong that surface tension doesn’t have much of an effect. The ‘elastic force’ of a solid is what makes a solid spring back to its original shape after you stop pushing on it. “As the solid gets stiffer, the liquid droplets need to be smaller in order to have this stiffening or cloaking effect. By embedding the solid with droplets of different materials, one can give it new electrical, optical or mechanical properties.


“It turns out that the importance of surface tension is inversely proportional to the size,” Dufresne said of the study. “So what’s just a negligible force for big things becomes a strong force for very small things–which in turn can strongly affect the material as a whole.”

The report, “Stiffening solids with liquid inclusions,” was completed by Drs. W. Style, Rostislav Boltyanskiy, Benjamin Allen, Katharine E.Jensen, Henry P. Foote, John S. Wettlaufer, and Eric R. Dufresne, and was published in December’s Nature Physics.


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Can electrons split? New evidence of exotic behaviors in quasi 2D magnetic materials

Can electrons split? New evidence of exotic behaviors in quasi 2D magnetic materials | Amazing Science | Scoop.it
Electrons may be seen as small magnets that also carry a negative electrical charge. On a fundamental level, these two properties are indivisible. However, in certain materials where the electrons are constrained in a quasi one-dimensional world, they appear to split into a magnet and an electrical charge, which can move freely and independently of each other. A longstanding question has been whether or not similar phenomenon can happen in more than one dimension. A team lead by EPFL scientists now has uncovered new evidence showing that this can happen in quasi two-dimensional magnetic materials. Their work is published in Nature Physics.


A strange phenomenon occurs with electrons in materials that are so thin that they can be thought of as being one-dimensional, e.g. nanowires. Under certain conditions, the electrons in these materials can actually split into an electrical charge and a magnet, which are referred to as "fractional particles". An important but still unresolved question in fundamental particle physics is whether this phenomenon could arise and be observed in more dimensions, like two- or three-dimensional systems.


Under temperatures close to absolute zero, electrons bind together to form an exotic liquid that can flow with exactly no friction. While this was previously observed at near-absolute zero temperatures in other materials, this electron liquid can form in cuprates at much higher temperatures that can be reached using liquid nitrogen alone. Consequently, there is currently an effort to find new materials displaying high-temperature superconductivity at room temperature. But understanding how it arises on a fundamental level has proven challenging, which limits the development of materials that can be used in applications. The advances brought by the EPFL scientists now bring support for the theory of superconductivity as postulated by Anderson.


"This work marks a new level of understanding in one of the most fundamental models in physics," says Henrik M. Rønnow. "It also lends new support for Anderson's theory of high-temperature superconductivity, which, despite twenty-five years of intense research, remains one of the greatest mysteries in the discovery of modern materials."

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New 'high-entropy' alloy is as light as aluminum but as strong as titanium alloys

New 'high-entropy' alloy is as light as aluminum but as strong as titanium alloys | Amazing Science | Scoop.it

High-entropy alloys are materials that consist of five or more metals in approximately equal amounts. These alloys are currently the focus of significant attention in materials science and engineering because they can have desirable properties. The research team combined lithium, magnesium, titanium, aluminum and scandium to make a nanocrystalline high-entropy alloy that has low density, but very high strength.


"The density is comparable to aluminum, but it is stronger than titanium alloys," says Dr. Carl Koch, Kobe Steel Distinguished Professor of Materials Science and Engineering at NC State and senior author of a paper on the work. "It has a combination of high strength and low density that is, as far as we can tell, unmatched by any other metallic material. The strength-to-weight ratio is comparable to some ceramics, but we think it's tougher - less brittle - than ceramics."


There are a wide range of uses for strong, lightweight materials, such as in vehicles or prosthetic devices. "We still have a lot of research to do to fully characterize this material and explore the best processing methods for it," Koch says.


At this point, the primary problem with the alloy is that it is made of 20 percent scandium, which is extremely expensive.

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Graphene shows promise for body armor, 8 to 10 times stronger than steel

Graphene shows promise for body armor, 8 to 10 times stronger than steel | Amazing Science | Scoop.it

Graphene could be used to make bulletproof armor. US researchers carried out miniature ballistic tests by firing tiny silica spheres at sheets of graphene. In the Science magazine they report that atom-thick layers of this material can be stronger than steel when it comes to absorbing impacts. Graphene consists of a sheet of single atoms arranged in a honeycomb structure.


It is thin, strong, flexible and electrically conductive, and has the potential to transform electronics as well as other technologies.

Jae-Hwang Lee from the University of Massachusetts in Amherst and colleagues used lasers to observe the silica "microbullets" as they penetrated sheets of graphene between 10 and 100 layers thick.

They compared the kinetic energy of the spheres before and after they pierced the graphene sheets.


Observations using an electron microscope revealed that graphene dissipates energy by stretching into a cone shape and then cracking in various directions. The mini-ballistic tests showed that grapheme's extraordinary strength, elasticity and stiffness allowed it to absorb between eight and 10 times the impacts that steel can withstand.

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Human climbing with efficiently scaled gecko-inspired dry adhesive

Human climbing with efficiently scaled gecko-inspired dry adhesive | Amazing Science | Scoop.it

Geckos are, objectively, way better at climbing stuff than people. Our big sweaty meathooks are no match for the wall-scaling optimized toe pads of a small lizard. That's why a team at Stanford University is busy making gloves that simulate the sticky grip of the gecko.


The Stanford team's secret ingredient for truly adhesive gecko-inspired hand pads is a type of silicone material called polydimethylsiloxane, which they layer as microscopic wedges. These wedges use something called van der Waals force to keep the wearer upright, which is exactly how geckos manage to crawl across ceilings without falling to a splatter. Right now, the synthetic pads only work on smooth surfaces like plastic and glass, so would-be Spidermen still can't outperform the gecko if they try to climb something rougher.


DARPA is working on a similar make-people-climb-like-geckos project, with special gecko-inspired paddles that also let people sidle up walls like a lizard. The Stanford team collaborated with DARPA here, too, but published more details about their results. The researchers believe this material could be useful in helping astronauts grab space debris, so really, what we're talking about here is just trying to avoid any of the plot points in Gravitybecoming a horrible reality.


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Method for symmetry-breaking in feedback-driven self-assembly of optical metamaterials

Method for symmetry-breaking in feedback-driven self-assembly of optical metamaterials | Amazing Science | Scoop.it

If you can uniformly break the symmetry of nanorod pairs in a colloidal solution, you're a step ahead of the game toward achieving new and exciting metamaterial properties. But traditional thermodynamic -driven colloidal assembly of these metamaterials, which are materials defined by their non-naturally-occurring properties, often result in structures with high degree of symmetries in the bulk material. In this case, the energy requirement does not allow the structure to break its symmetry.


In a study led by Xiang Zhang, director of Berkeley Lab's Materials Sciences Division, he and his research group at the University of California (UC) Berkeley achieved symmetry-breaking in a bulk metamaterial solution for the first time. Zhang and his group demonstrated self-assembled optical metamaterials with tailored broken-symmetries and hence unique electromagnetic responses that can be achieved via their new method. The results have been published in Nature Nanotechnology. The paper is titled "Feedback-driven self-assembly of symmetry-breaking optical metamaterials in solution."


"We developed an innovative self-assembly route which could surpass the conventional thermodynamic limit in chemical synthetic systems" explains Sui Yang, lead author of the Nature Nanotechnology paper and member of Zhang's research group. "Specifically, we use the material's own property as a self-correction feedback mechanism to self-determine the final structure."


This led the group to produce nanostructures that have historically been considered impossible to assemble. The widely used method of metamaterial synthesis is top-down fabrication such as electron beam or focus ion beam lithography that often results in strongly anisotropic and small-scale metamaterials.


"People build metamaterials using top-down methods that include light exposure and electron beam exposure, which are inefficient and costly," says Xingjie Ni, another lead author on the paper. "If we want to use metamaterials, we need to develop a way to build them cheaply and efficiently."

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Biomedical Sensors That Dissolve in Your Body and Reduce Infection and Waste

Biomedical Sensors That Dissolve in Your Body and Reduce Infection and Waste | Amazing Science | Scoop.it

John Rogers, a professor of engineering at the University of Illinois at Urbana-Champaign, was the lead author on a recent study published in the journal Advanced Materials. This study tested biodegradable printed circuit boards, a very efficient type of sensor with a large surface area. In the study, Rogers and his team showed they had effectively created a sensor that both does its job and is fully dissolvable.


Rogers spearheads a lab that has been at the forefront of this technology since 2008. When they were first getting started in the field of biodegradable sensors, the researchers spent several years coming up with the materials and processes that worked, Rogers said in an email. “Our research now is focusing on systems and applications, in areas ranging from biomedicine to consumer electronics,” he added.


The semiconductor, the part of the device that does the sensing, is made of two materials. One is extremely thin silicon, which the researchers shave down to the nano scale. They combine the silicon with metals that are familiar components of food and vitamins, like magnesium, zinc, and iron. The sensor is encapsulated by and rests on a set of polymers that, Rogers said, “are already used, for other purposes, in the body.”


Rogers and his team are still perfecting the sensors, but they anticipate that they could even work wirelessly by transmitting information via radio waves back to doctors’ devices. Typically, the silicon dissolves in the body in a few weeks, Rogers said, but different substances could extend the device’s lifespan.


Devices like these have the potential to change medicine for the better. Currently, the infection rate for surgeries—including the procedure needed to implant a biomedical device—is 1 to 3 percent. Usually this happens because the wound gets contaminated.


The logic for Rogers’ devices is simple: when doctors have to cut a person open less often, there’s less chance of infection. And the devices could be used as more than sensors; they could administer programmed drug delivery for conditions that require daily injections, or reduce pain by stimulating stressed nerve endings.


There are also environmental implications. In an effort to decrease the chance of infection, the health industry has relied for years on disposable, one-use devices, from syringes to hospital gowns. The result is that medical facilities generate billions of tons of trash per year, although no one is sure exactly how much. And although much of this trash could be recycled with the proper treatment, almost all of it just ends up in landfills, where it biodegrades very slowly and could present potential health hazards if people are exposed to it. Dissolvable, biodegradable devices would mean less waste in a landfill, and if a device did end up there, it would decompose rapidly.


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New 'smart' material improves removal of arsenic from drinking water

New 'smart' material improves removal of arsenic from drinking water | Amazing Science | Scoop.it

Scientists have created a new material that can remove double the amount of arsenic from water than the leading material for water treatment. Arsenic is a toxic element found naturally in groundwater. Long-term exposure over a number of years to elevated concentrations of arsenate, the chemical form of arsenic in water, is associated with debilitating, and potentially fatal, illnesses including cancer, heart and lung disease, gastrointestinal problems and neurological disorders.


Arsenic-contaminated drinking water has been identified in many countries across the globe, including Bangladesh, Chile, Mexico, Argentina, Australia, USA and parts of the UK. Recent estimates suggest that more than 200 million people are unknowingly exposed to unsafe levels of arsenic in their drinking water.  


In a new study published inChemistry - A European Journal, scientists at Imperial College London have designed, tested and patented a new zinc-based material that can selectively bind to arsenate with strong affinity. The scientists hope this material could ultimately be used to improve quality of domestic water filters and reduce the amount of arsenic that people are exposed to, in areas with known or suspected high arsenic content.


In 2006 the World Health Organization issued guidelines defining safe concentration levels of arsenic as 10 parts per billion but several countries affected by arsenic-contaminated groundwater have legal concentration limits above this guideline and recent evidence suggests that long-term exposure to smaller concentrations can be harmful.


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New Omnidirectional Broadband 2D Crystal Efficiently Absorbs 85% Of Photon Energy

New Omnidirectional Broadband 2D Crystal Efficiently Absorbs 85% Of Photon Energy | Amazing Science | Scoop.it

Research engineers at MIT have developed a novel solar material in the form of a 2D metallic, dielectric photonic crystal.  The material has remarkable properties of broadband absorption of sunlight, from visible to near infrared portions of the spectrum, with little dependence on the angle of the incident light.  Efficiencies in these bands were measured to be 85% absorption of photons.

The material also withstands temperatures up to 1000 degrees Celsius, making it suitable to act as the material for a collector of concentrated sunlight.  Experiments show that the absorption is governed by the nanocavities.  Tuning the absorption bands is accomplished simply by varying the radii and depths of the cavities.


The new material works as a part of the solar-thermophotovoltaic (STPV) device in which incident solar radiation is converted to infrared, heat energy, causing the material to emit light that is in turn converted to electrical energy.   Earlier STPV devices contained nanocavities but were hollow and not filled with a dielectric.  According to the primary author, “They were empty, there was air inside.  No one had tried putting a dielectric material inside, so we tried that and saw some interesting properties.”  A dielectric is a material which responds to electric fields by shielding or attenuating it via non-mobile charges, in contrast to a conductor which shields by rearrangement of electrons.


The cavities are sized in the right way such that there is a rich and complex absorption mode structure perfect for relevant wavelengths.  “You can tune the absorption just by changing the size of the nanocavities,” said Dr. Chou.


Importantly, the new material is compatible with many kinds of existing manufacturing technologies.  The lead author Dr. Chou said “This is the first-ever device of this kind that can be fabricated with a method based on current techniques, which means it’s able to be manufactured on silicon wafer scales.”


Prior work on similar materials were restricted in size to making devices that span only a few inches.  The new cavity material is both cheaper and easier to process.

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Bioinspired coating for medical devices repels blood and bacteria

Bioinspired coating for medical devices repels blood and bacteria | Amazing Science | Scoop.it
From joint replacements to cardiac implants and dialysis machines, medical devices enhance or save lives on a daily basis. However, any device implanted in the body or in contact with flowing blood faces two critical challenges that can threaten the life of the patient the device is meant to help: blood clotting and bacterial infection.

A team of Harvard scientists and engineers may have a solution. They developed a new surface coating for medical devices using materials already approved by the Food and Drug Administration (FDA). The coating repelled blood from more than 20 medically relevant substrates the team tested — made of plastic to glass and metal — and also suppressed biofilm formation in a study reported in Nature Biotechnology. But that's not all.

The team implanted medical–grade tubing and catheters coated with the material in large blood vessels in pigs, and it prevented blood from clotting for at least eight hours without the use of blood thinners such as heparin. Heparin is notorious for causing potentially lethal side–effects like excessive bleeding but is often a necessary evil in medical treatments where clotting is a risk.

"Devising a way to prevent blood clotting without using anticoagulants is one of the holy grails in medicine," said Don Ingber, M.D., Ph.D., Founding Director of Harvard's Wyss Institute for Biologically Inspired Engineering and senior author of the study. Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Boston Children's Hospital, as well as professor of bioengineering at Harvard School of Engineering and Applied Sciences (SEAS).
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Hybrid materials could smash the solar efficiency ceiling by extracting electrons from dark triplet excitons

Hybrid materials could smash the solar efficiency ceiling by extracting electrons from dark triplet excitons | Amazing Science | Scoop.it
Researchers have developed a new method for harvesting the energy carried by particles known as ‘dark’ spin-triplet excitons with close to 100% efficiency, clearing the way for hybrid solar cells which could far surpass current efficiency limits.


The team, from the University of Cambridge, have successfully harvested the energy of triplet excitons, an excited electron state whose energy in harvested in solar cells, and transferred it from organic to inorganic semiconductors. To date, this type of energy transfer had only been shown for spin-singlet excitons. The results are published in the journal Nature Materials.


In the natural world, excitons are a key part of photosynthesis: light photons are absorbed by pigments and generate excitons, which then carry the associated energy throughout the plant. The same process is at work in a solar cell.


In conventional semiconductors such as silicon, when one photon is absorbed it leads to the formation of one free electron that can be extracted as current. However, in pentacene, a type of organic semiconductor, the absorption of a photon leads to the formation of two electrons. But these electrons are not free and they are difficult to pin down, as they are bound up within ‘dark’ triplet exciton states.

Excitons come in two ‘flavours’: spin-singlet and spin-triplet. Spin-singlet excitons are ‘bright’ and their energy is relatively straightforward to harvest in solar cells. Triplet-spin excitons, in contrast, are ‘dark’, and the way in which the electrons spin makes it difficult to harvest the energy they carry.


“The key to making a better solar cell is to be able to extract the electrons from these dark triplet excitons,” said Maxim Tabachnyk, a Gates Cambridge Scholar at the University’s Cavendish Laboratory, and the paper’s lead author. “If we can combine materials like pentacene with conventional semiconductors like silicon, it would allow us to break through the fundamental ceiling on the efficiency of solar cells.”

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World's first "solar battery" runs on light and air and stores its own power

World's first "solar battery" runs on light and air and stores its own power | Amazing Science | Scoop.it

Researchers at The Ohio State University have invented a solar battery -- a combination solar cell and battery -- which recharges itself using air and light. The design required a solar panel which captured light, but admitted air to the battery. Here, scanning electron microscope images show the solution: nanometer-sized rods of titanium dioxide (larger image) which cover the surface of a piece of titanium gauze (inset). The holes in the gauze are approximately 200 micrometers across, allowing air to enter the battery while the rods gather light. Image courtesy of Yiying Wu, The Ohio State University.


When the battery discharges, it chemically consumes oxygen from the air to re-form the lithium peroxide. An iodide additive in the electrolyte acts as a “shuttle” that carries electrons, and transports them between the battery electrode and the mesh solar panel. The use of the additive represents a distinct approach on improving the battery performance and efficiency, the team said.


The mesh belongs to a class of devices called dye-sensitized solar cells, because the researchers used a red dye to tune the wavelength of light it captures.


In tests, they charged and discharged the battery repeatedly, while doctoral student Lu Ma used X-ray photoelectron spectroscopy to analyze how well the electrode materials survived—an indication of battery life.


First they used a ruthenium compound as the red dye, but since the dye was consumed in the light capture, the battery ran out of dye after eight hours of charging and discharging—too short a lifetime. So they turned to a dark red semiconductor that wouldn’t be consumed: hematite, or iron oxide—more commonly called rust.


Coating the mesh with rust enabled the battery to charge from sunlight while retaining its red color. Based on early tests, Wu and his team think that the solar battery’s lifetime will be comparable to rechargeable batteries already on the market.


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Platinum meets its match in quantum dots from coal

Platinum meets its match in quantum dots from coal | Amazing Science | Scoop.it

Graphene quantum dots created at Rice University grab onto graphene platelets like barnacles attach themselves to the hull of a boat. But these dots enhance the properties of the mothership, making them better than platinum catalysts for certain reactions within fuel cells.


The Rice lab of chemist James Tour created dots known as GQDs from coal last year and have now combined these nanoscale dots with microscopic sheets of graphene, the one-atom-thick form of carbon, to create a hybrid that could greatly cut the cost of generating energy with fuel cells. - See more at: f


The research is the subject of a new paper in the American Chemical Society journal ACS Nano.


The lab discovered boiling down a solution of GQDs and graphene oxide sheets (exfoliated from common graphite) combined them into self-assembling nanoscale platelets that could then be treated with nitrogen and boron. The hybrid material combined the advantages of each component: an abundance of edges where chemical reactions take place and excellent conductivity between GQDs provided by the graphene base. The boron and nitrogen collectively add more catalytically active sites to the material than either element would add alone.


“The GQDs add to the system an enormous amount of edge, which permits the chemistry of oxygen reduction, one of the two needed reactions for operation in a fuel cell,” Tour said. “The graphene provides the conductive matrix required. So it’s a superb hybridization.”

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Switching to Spintronics: Berkeley Researchers Used Electric Field to Reverse Magnetization in Multiferroic

Switching to Spintronics: Berkeley Researchers Used Electric Field to Reverse Magnetization in Multiferroic | Amazing Science | Scoop.it

In a development that holds promise for future magnetic memory and logic devices, researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Cornell University successfully used an electric field to reverse the magnetization direction in a multiferroic spintronic device at room temperature. This demonstration, which runs counter to conventional scientific wisdom, points a new way towards spintronics and smaller, faster and cheaper ways of storing and processing data.


“Our work shows that 180-degree magnetization switching in the multiferroic bismuth ferrite can be achieved at room temperature with an external electric field when the kinetics of the switching involves a two-step process,” says Ramamoorthy Ramesh, Berkeley Lab’s Associate Laboratory Director for Energy Technologies, who led this research. “We exploited this multi-step switching process to demonstrate energy-efficient control of a spintronic device.”


Ramesh, who also holds the Purnendu Chatterjee Endowed Chair in Energy Technologies at the University of California (UC) Berkeley, is the senior author of a paper describing this research in Nature. The paper is titled “Deterministic switching of ferromagnetism at room temperature using an electric field.” John Heron, now with Cornell University, is the lead and corresponding author.


“The electrical currents that today’s memory and logic devices rely on to generate a magnetic field are the primary source of power consumption and heating in these devices,” he says. “This has triggered significant interest in multiferroics for their potential to reduce energy consumption while also adding functionality to devices.” To demonstrate the potential technological applicability of their technique, Ramesh, Heron and their co-authors used heterostructures of bismuth ferrite and cobalt iron to fabricate a spin-valve, a spintronic device consisting of a non-magnetic material sandwiched between two ferromagnets whose electrical resistance can be readily changed. X-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) images showed a clear correlation between magnetization switching and the switching from high-to-low electrical resistance in the spin-valve. The XMCD-PEEM measurements were completed at PEEM-3, an aberration corrected photoemission electron microscope at beamline 11.0.1 of Berkeley Lab’s Advanced Light Source.

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Chemists Fabricate Novel Rewritable Paper Using Color Switching Redox Dyes

Chemists Fabricate Novel Rewritable Paper Using Color Switching Redox Dyes | Amazing Science | Scoop.it

First developed in China in about the year A.D. 150, paper has many uses, the most common being for writing and printing upon.  Indeed, the development and spread of civilization owes much to paper’s use as writing material. According to surveys, 90 percent of all information in businesses used today is retained on paper, even though the bulk of this printed paper is discarded after just one-time use. This is such a waste of paper and ink cartridges — not to mention the accompanying environmental problems such as deforestation and chemical pollution to air, water and land—could be curtailed if the paper were “rewritable,” that is, capable of being written on and erased multiple times.


Chemists at the University of California, Riverside have now fabricated in the lab just such novel rewritable paper, one that is based on the color switching property of commercial chemicals called redox dyes.  The dye forms the imaging layer of the paper.  Printing is achieved by using ultraviolet light to photobleach the dye, except the portions that constitute the text on the paper.  The new rewritable paper can be erased and written on more than 20 times with no significant loss in contrast or resolution.


“This rewritable paper does not require additional inks for printing, making it both economically and environmentally viable,” said Yadong Yin, a professor of chemistry, whose lab led the research. “It represents an attractive alternative to regular paper in meeting the increasing global needs for sustainability and environmental conservation.”


The rewritable paper is essentially rewritable media in the form of glass or plastic film to which letters and patterns can be repeatedly printed, retained for days, and then erased by simple heating.


The paper comes in three primary colors: blue, red and green, produced by using the commercial redox dyes methylene blue, neutral red and acid green, respectively.  Included in the dye are titania nanocrystals (these serve as catalysts) and the thickening agent hydroxyethyl cellulose (HEC).  The combination of the dye, catalysts and HEC lends high reversibility and repeatability to the film.


During the writing phase, ultraviolet light reduces the dye to its colorless state.  During the erasing phase, re-oxidation of the reduced dye recovers the original color; that is, the imaging material recovers its original color by reacting with ambient oxygen.  Heating at 115 C can speed up the reaction so that the erasing process is often completed in less than 10 minutes. “The printed letters remain legible with high resolution at ambient conditions for more than three days – long enough for practical applications such as reading newspapers,” Yin said. “Better still, our rewritable paper is simple to make, has low production cost, low toxicity and low energy consumption.”

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Superconductivity without cooling - but only for a few picoseconds

Superconductivity without cooling - but only for a few picoseconds | Amazing Science | Scoop.it

Superconductivity is a remarkable phenomenon: superconductors can transport electric current without any resistance and thus without any losses whatsoever. It is already in use in some niche areas, for example as magnets for nuclear spin tomography or particle accelerators. However, the materials must be cooled to very low temperatures for this purpose. But during the past year, an experiment has provided some surprises.


With the aid of short infrared laser pulses, researchers have succeeded for the first time in making a ceramic superconducting at room temperature – albeit for only a few millionths of a microsecond. An international team, in which physicists from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg have made crucial contributions, has now been able to present a possible explanation of the effect in the journal Nature: The scientists believe that laser pulses cause individual atoms in the crystal lattice to shift briefly and thus enhance the superconductivity.


In the beginning, superconductivity was known only in a few metals at temperatures just above absolute zero at minus 273 degrees Celsius. Then, in the 1980s, physicists discovered a new class, based on ceramic materials. These already conduct electricity at temperatures of around minus 200 degrees Celsius without losses, and were therefore called high-temperature superconductors. One of these ceramics is the compound yttrium barium copper oxide (YBCO). It is one of the most promising materials for technical applications such as superconducting cables, motors and generators.


The YBCO crystal has a special structure: thin double layers of copper oxide alternate with thicker intermediate layers which contain barium as well as copper and oxygen. The superconductivity has its origins in the thin double layers of copper dioxide. This is where electrons can join up to form so-called Cooper pairs. These pairs can "tunnel" between the different layers, meaning they can pass through these layers like ghosts can pass through walls, figuratively speaking – a typical quantum effect. The crystal only becomes superconducting below a "critical temperature", however, as only then do the Cooper pairs tunnel not only within the double layers, but also "spirit" through the thicker layers to the next double layer. Above the critical temperature, this coupling between the double layers is missing, and the material becomes a poorly conducting metal.


In 2013, an international team working with Max Planck researcher Andrea Cavalleri discovered that when YBCO is irradiated with infrared laser pulses it briefly becomes superconducting at room temperature. The laser light had apparently modified the coupling between the double layers in the crystal. The precise mechanism remained unclear, however – until the physicists were able to solve the mystery with an experiment at the LCLS in the US, the world's most powerful X-ray laser. "We started by again sending an infrared pulse into the crystal, and this excited certain atoms to oscillate," explains Max Planck physicist Roman Mankowsky, lead author of the current Nature study. "A short time later, we followed it with a short X-ray pulse in order to measure the precise crystal structure of the excited crystal." The infrared pulse had not only excited the atoms to oscillate, but had also shifted their position in the crystal as well. This briefly made the copper dioxide double layers thicker - by two picometres, or one hundredth of an atomic diameter - and the layer between them became thinner by the same amount. This in turn increased the quantum coupling between the double layers to such an extent that the crystal became superconducting at room temperature for a few picoseconds.

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A time cloak that conceals events rather than objects

A time cloak that conceals events rather than objects | Amazing Science | Scoop.it

A "time cloak" that conceals events rather than objects can hide secret messages through a trick of light, making information invisible to all but the intended recipient. Like an invisibility cloak that makes something disappear in plain sight, a time cloak makes an event disappear in time. It works by manipulating light traveling along an optical fiber.


Imagine a row of cars speeding along a road slowing down in concert to create brief paths for pedestrians to safely cross. When the cars that let the pedestrians cross ahead of them speed up and re-join the rest of the traffic, no one can tell there was ever a gap in the flow – the pedestrians' presence has been cloaked. In the same way, photons' paths can be tweaked to create brief gaps where information can safely hide.


Last year, a team at Purdue University in Indiana built a cloak that could transfer hidden data at 1.5 gigabits a second, fast enough to make it theoretically useful for real communication. The only thing was, the message was hidden so well that no one could actually read it. That problem has now been solved.


"With this new device, we don't just limit ourselves to thinking about cloaks as a way of preventing somebody from getting information, but also as a way to enable communication," says Joseph Lukens, an electrical engineer at Purdue. "One guy sees nothing, the other guy sees everything."


Lukens and his colleagues created two different communications channels using lasers tuned to two different frequencies. One is a regular frequency and the other is a time-cloaked channel that remains hidden unless you know it's there. Photons from each laser traveled along the same fibre, but the intended recipient just needs to tune in to the right channel to reveal the secret information.


Not only could the cloak deliver the messages, it also successfully fended off outside attempts to scramble the information. A similar device could one day improve current communication systems, says Moti Fridman at Bar-Ilan University in Israel.

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Extreme Graphene and the Coming Super Materials' Gold Rush

Extreme Graphene and the Coming Super Materials' Gold Rush | Amazing Science | Scoop.it

In 2004, scientists Andre Geim and Kostya Novoselov from the University of Manchester, used adhesive tape to lift a thin layer of carbon from a block of graphite, and placed it on a silicone wafer. Graphite is the stuff commonly found in pencil lead. As simple as this sounds, what these two scientists had created was a 2-dimensional form of carbon known as graphene, and in 2010 they received the Nobel Prize in Physics for this discovery. But that’s only part of the story. What makes the discovery of graphene so important is all of its unusual properties. It is a pure form of carbon that is very thin, very strong and very expensive.


  • SUPER THIN – It is only one atom thick, so it is almost transparent.
  • SUPER STRONG – Graphene is the strongest material ever discovered, 100 times stronger than diamond, and 200 times stronger than steel, and yet flexible and even stretchable.
  • SUPER CONDUCTOR – It conducts heat and electricity faster at room temperature than any other known material. It also charges and discharges electrically up to 1000x faster than traditional batteries.
  • SUPER EXPENSIVE – Even using the most advanced processes for manufacturing it, graphene still runs around about $100,000 per square meter.


These unusual attributes have made graphene the most exciting new material in all of science.  Since its discovery, a total of 8,413 patents were granted by February 2013 in areas such as super computing, electronics, energy storage, telecommunications, renewable power, health care, and telecommunications. That said, we are about to embark on the golden age of material science with digitally modeled materials being fabricated and used in thousands of experimental applications before landing on their primary uses in the business arena.


  • Aerogels are a synthetic porous ultralight material created with a process that replaces the liquid component of a gel with gas. The result is solid matter, typically carbon, but with extremely low density and low thermal conductivity. Sometimes researchers refer to it as “frozen smoke.” Its current uses include insulation for skylights, chemical absorber for cleaning up spills, thickening agents in some paints and cosmetics, drug delivery agents, and water purification. But we are only scratching the surface of the thousands of other uses still to come.
  • Stanene (two-dimensional tin sheets) may be the next super material that competes with graphene. Even though it’s still only a theoretical substance that’s never actually been produced, it has lots of the thought leaders in material science world buzzing.
  • Shrilk is a material made from leftover shrimp shells and proteins derived from silk. Its dissolve-over-time biodegradable attributes will allow it to serve as sutures or scaffolds for growing new tissues that disappear when they are no longer needed.
  • Biomimetic nanomaterials are just now coming online. As an example, lotus leaves that are resistant to wetting and dirt due to their nanostructured surface are being used to develop waterproof paints and textiles.
  • Growable metals are still only in the backroom laboratory stage, but speculation has them being developed by adding metal salts to the irrigation water in plants, and using a secret process to sort the metals from the organic matter.
  • Spider silk is made from a biopolymer called an aquamelt, which can be spun at room temperature 1,000 times more efficiently than plastics. While spider silk itself will probably never be used, researchers are looking to make other materials that mimic spider silk’s tricks.
  • Carbon nanotubes are members of the fullerene structural family. Being carbon-based like graphene, carbon nanotubes compete on many levels with graphene in areas such as strength, conductivity, and stiffness. Even though the first paper describing carbon nanotubes appeared in 1991, no one has yet cracked the code for producing long strands inexpensively.


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Droplets made to order

Droplets made to order | Amazing Science | Scoop.it
New method allows microdroplets of any shape to form on a surface.


Understanding liquid dynamics on surfaces can provide insight into nature’s design and enable fine manipulation capability in biological, manufacturing, microfluidic and thermal management applications. Of particular interest is the ability to control the shape of the droplet contact area on the surface, which is typically circular on a smooth homogeneous surface. A research team now shows the ability to tailor various droplet contact area shapes ranging from squares, rectangles, hexagons, octagons, to dodecagons via the design of the structure or chemical heterogeneity on the surface. They simultaneously obtain the necessary physical insights to develop a universal model for the three-dimensional droplet shape by characterizing the droplet side and top profiles. Furthermore, arrays of droplets with controlled shapes and high spatial resolution can be achieved using this approach. This liquid-based patterning strategy promises low-cost fabrication of integrated circuits, conductive patterns and bio-microarrays for high-density information storage and miniaturized biochips and biosensors, among others.

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Acoustic Metamaterial Superenhances Current Weak Sound Detection Limits By More Than 10 Fold

Acoustic Metamaterial Superenhances Current Weak Sound Detection Limits By More Than 10 Fold | Amazing Science | Scoop.it

Metamaterials are composite materials with exacting, repetitive subwavelength structural patterns that have properties not found in nature.  Thus far, they have been used to create novel optical materials with negative index of refraction, thus permitting “superlenses” that have enhanced optical resolution beyond conventional lenses, and “invisibility cloaks” that bend at least a narrow band of radiation around a cloaked object.


A group of researchers from the University of Maryland (UMD) have created, using a combination of theory, computation, and experimentation, a new acoustic metamaterial that dramatically amplifies acoustic signals, more than 10 times past the detection limit of conventional sensors.


The key property of the novel metamaterial is its “graded refractive index” or GRIN for short.  The ideal GRIN material has an increasing index of refraction along one axis, but constant along the other two axes. This is realized physically by a tapered slab made up of a regular stacked array of stainless steel plates, each one separated by a gap of air 1.4 mm wide.  The distance between plates is 3.4 mm. The height and thickness of the stainless steel plates are given by 40 mm and 2 mm respectively. The width of each increases from 0.5 to 50 mm with an increment of 0.5 mm.  Other ways of instantiating a GRIN material are possible.


Sounds waves projected along the axis perpendicular to the plates experience a compressive effect, causing an increase in the frequency of the sound and concentrating the energy into a smaller volume space mostly along the direction of travel.  The compression intensifies or amplifies the sound pressure wave, before reaching a sensor or detector at the end.  The sensor then detects the strongly amplified sound wave, which prior to its travel into the device may have been near or below the detection threshold with a signal-to-noise (SNR) ratio of less than or equal to 1.


The material has a number of other advantages.  In the electromagnetic domain it is immune to interference, possesses low intrinsic noise, and is highly sensitive.  In the acoustic domain it is amplifying in pressure waves and able to accept different frequencies in multiplex.  In an experiment the experimenters showed that a very weak signal, at only 27% the strength of ambient noise (SNR of 0.27), can be amplified substantially over 100-fold, bringing the SNR up to 32.7.  The metamaterial by virtue of its waveguide and pressure amplification overcomes the detection limit of conventional acoustic sensors.

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Noncovalent, Self-Assembled, Robust, Porous Material That Adsorbs Greenhouse Gas

Noncovalent, Self-Assembled, Robust, Porous Material That Adsorbs Greenhouse Gas | Amazing Science | Scoop.it

Researchers from the Department of Chemistry at the University of Houston have created noncovalent organic frameworks, a new type of porous material that overcomes some barriers in the development of porous material technologies.  The new wonder material is highly processable, self-assembled, possessing of a superstructure with large, 16 angstrom pores (Figure above).  The material has a high affinity for hydrocarbons suggesting applications for use as an energy storage substrate.  In addition, the material also captures CFCs and fluorocarbons, both potent greenhouse gas species.  The capture capacity is up to 75% of the original weight.


The field of porous materials has experienced two other, prior twin advances in the area of metal-organic and covalent organic frameworks though they are plagued by the problem of low processability as the extended crystalline structure makes them impossible to dissolve without decomposition.


Remarkably, the building block of the noncovalent porous material is a single molecule trispyrazole, which stack and self-assemble into a large, porous, crystal-like configuration.  The author characterizes the pores as “infinite one-dimensional channels protruding throughout the crystal along the crystallographic c axis”.  The interior “lining” of the channels is arrayed with fluorines.


The entire super structure is stabilized by noncovalent hydrogen bonds and “pi-pi” stacking – hallmarks of a “supramolecular” material.  H-bonds and pi-interactions  are considered “weak” associations between molecules, but by virtue of the sheer number and surface area of interactions, the material turns out to be thermally very stable (up to 250 degrees C) and resistant to solvents, acids and bases.  Engineers interested in manipulating the material would find most interesting that its solubility in DMSO can be tuned by temperature.


Of great interest in porous materials is measurement of the “effective surface area” in the pores, for a given weight of the porous material.  A common measure of the surface area is the Brunauer–Emmett–Teller surface area.  Using nitrogen adsorption measurements the surface area was determined to be 1,159 m2 g−1.  For comparison activated charcoal used in water filters has a surface area of about 500 m2 g−1.  The high surface area is the reason for the high capture weight proportion (75%).

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How to hide like an octopus: New materials to quickly change color and texture

How to hide like an octopus: New materials to quickly change color and texture | Amazing Science | Scoop.it
Researchers create materials that reproduce cephalopods’ ability to quickly change colors and textures.


Cephalopods, which include octopuses, squid, and cuttlefish, are among nature’s most skillful camouflage artists, able to change both the color and texture of their skin within seconds to blend into their surroundings — a capability that engineers have long struggled to duplicate in synthetic materials. Now a team of researchers has come closer than ever to achieving that goal, creating a flexible material that can change its color or fluorescence and its texture at the same time, on demand, by remote control.


The results of their research have been published in the journal Nature Communications, in a paper by a team led by MIT Assistant Professor of Mechanical Engineering Xuanhe Zhao and Duke University Professor of Chemistry Stephen Craig.


Zhao, who joined the MIT faculty from Duke this month and holds a joint appointment with the Department of Civil and Environmental Engineering, says the new material is essentially a layer of electro-active elastomer that could be quite easily adapted to standard manufacturing processes and uses readily available materials. This could make it a more economical dynamic camouflage material than others that are assembled from individually manufactured electronic modules.


While its most immediate applications are likely to be military, Zhao says the same basic approach could eventually lead to production of large, flexible display screens and anti-fouling coatings for ships.


In its initial proof-of-concept demonstrations, the material can be configured to respond with changes in both texture and fluorescence, or texture and color. In addition, while the present version can produce a limited range of colors, there is no reason that the range of the palette cannot be increased, Craig says.

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Team's curator insight, October 16, 2014 10:47 AM

Philippe: le titre est interessant

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Casting Custom-Shaped Inorganic Structures with DNA Molds

Casting Custom-Shaped Inorganic Structures with DNA Molds | Amazing Science | Scoop.it
Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have unveiled a new method to form tiny 3D metal nanoparticles in prescribed shapes and dimensions using DNA, Nature's building block, as a construction mold.

The ability to mold inorganic nanoparticles out of materials such as gold and silver in precisely designed 3D shapes is a significant breakthrough that has the potential to advance laser technology, microscopy, solar cells, electronics, environmental testing, disease detection and more.

"We built tiny foundries made of stiff DNA to fabricate metal nanoparticles in exact three–dimensional shapes that we digitally planned and designed," said Peng Yin, senior author of the paper, Wyss Core Faculty member and Assistant Professor of Systems Biology at Harvard Medical School.


The Wyss team's findings, described in a paper titled "Casting Inorganic Structures with DNA Molds," were published today in Science. The work was done in collaboration with MIT's Laboratory for Computational Biology and Biophysics, led by Mark Bathe, senior co–author of the paper.


"The paper's findings describe a significant advance in DNA nanotechnology as well as in inorganic nanoparticle synthesis," Yin said. For the very first time, a general strategy to manufacture inorganic nanoparticles with user-specified 3D shapes has been achieved to produce particles as small as 25 nanometers or less, with remarkable precision (less than 5 nanometers). A sheet of paper is approximately 100,000 nanometers thick.


The 3D inorganic nanoparticles are first conceived and meticulously planned using computer design software. Using the software, the researchers design three–dimensional "frameworks" of the desired size and shape built from linear DNA sequences, which attract and bind to one another in a predictable manner.


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High Efficiency Achieved for Harvesting Hydrogen Fuel From the Sun using Earth-Abundant Materials

High Efficiency Achieved for Harvesting Hydrogen Fuel From the Sun using Earth-Abundant Materials | Amazing Science | Scoop.it

Today, the journal Science published the latest development in Michael Grätzel’s laboratory at EPFL: producing hydrogen fuel from sunlight and water. By combining a pair of solar cells made with a mineral called perovskite and low cost electrodes, scientists have obtained a 12.3 percent conversion efficiency from solar energy to hydrogen, a record using earth-abundant materials as opposed to rare metals.

The race is on to optimize solar energy’s performance. More efficient silicon photovoltaic panels, dye-sensitized solar cells, concentrated cells and thermodynamic solar plants all pursue the same goal: to produce a maximum amount of electrons from sunlight. Those electrons can then be converted into electricity to turn on lights and power your refrigerator.

At the Laboratory of Photonics and Interfaces at EPFL, led by Michael Grätzel, where scientists invented dye solar cells that mimic photosynthesis in plants, they have also developed methods for generating fuels such as hydrogen through solar water splitting. To do this, they either use photoelectrochemical cells that directly split water into hydrogen and oxygen when exposed to sunlight, or they combine electricity-generating cells with an electrolyzer that separates the water molecules.

By using the latter technique, Grätzel’s post-doctoral student Jingshan Luo and his colleagues were able to obtain a performance so spectacular that their achievement is being published today in the journal Science. Their device converts into hydrogen 12.3 percent of the energy diffused by the sun on perovskite absorbers – a compound that can be obtained in the laboratory from common materials, such as those used in conventional car batteries, eliminating the need for rare-earth metals in the production of usable hydrogen fuel.

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Russell R. Roberts, Jr.'s curator insight, October 7, 2014 3:23 AM

This development  could be a game changer when it comes to alternate energy. The Michael Gratzel Laboratory at EPFL has produced hydrogen from sunlight and water.  By connecting a pair of solar cells made from a common material known as perovskite and low-cost electrodes, scientists "have obtained a 12.3% conversion from solar energy to hydrogen...a record using earth-abundant materials as opposed to rare metals."  The day is coming when common metals, such as those used  in automobile batteries, will be joined with solar panels to produce the most abundant fuel in the universe--hydrogen.  Hydrogen-powered vehicles are in development now by several car manufacturers, including Ford, GM, Nissan, Toyota, Honda, Mercedes, and BMW.  Current hybrid vehicles require expensive Lithium-Ion batteries and exotic metals available in only a few countries.  Once easily produced hydrogen fuel is available, our dependence on unfriendly regimes for key metals will diminish.  Couple that with a reduced demand for foreign oil, this country may adopt a more realistic, objective foreign policy.  Aloha, Russ.

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A Spoonful of a New Crystalline Material Can Absorb a Whole Roomful of Oxygen

A Spoonful of a New Crystalline Material Can Absorb a Whole Roomful of Oxygen | Amazing Science | Scoop.it

A team of scientists at the Universiy of Southern Denmark just invented a crystalline material that can absorb oxygen with astounding efficiency. How astounding? Well, a single spoonful of the stuff can suck all of the oxygen out of a room. The best part is that it can release it again with just a little bit of heat. Say goodbye to bulky oxygen tanks.

"The material can absorb and release oxygen many times without losing the ability. It is like dipping a sponge in water, squeezing the water out of it and repeating the process over and over again," says Professor Christine McKenzie who led the research. "When the substance is saturated with oxygen, it can be compared to an oxygen tank, containing pure oxygen under pressure. The difference is that this material can hold three times as much oxygen."


In other words, a patient with lung trouble or a scuba diver wouldn't need to carry around heavy oxygen tanks. Instead, they could take advantage of this new cobalt-based material in a doubtlessly smaller container. Something as small as a mask could replace complex oxygen tank-and-pump setups. And yes, the scientists say that it will work underwater.


New ways to capture and store oxygen bear massive implications not only for medical technology but also for hydrogen fuel cells. The team in Denmark is now exploring the possibilities which extend all the way to artificial photosynthesis. That said, one can't help but wonder how this material might be weaponized. But let's just focus on the positive for now: Pocket-sized scuba kits here we come.

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