3D-printed composite is lighter than wood and stiffer than concrete

Reseachers at Harvard University have developed a way to 3D-print a cellular composite with record lightness and stiffness using an epoxy resin. This marks the first time that epoxy is used for 3D-printing, and the advance could lead to the development of new lightweight architectures for more efficient wind turbines, faster cars, and lighter airplanes.

If you take all of the materials known to man, whether natural or man-made, and observe their relative properties, you’ll soon find a very clear pattern: density and strength always seem to go hand-in-hand. The very light foams are generally extremely weak, and on the other end of the spectrum, the heavy materials like steels and other metals are among the strongest we know.

There are, however, a few outliers. One such example is balsa wood, which has a density as low as 40 kg per cubic meter (2.5 lb per cubic foot) but is still very strong, thanks to a microscopic structure that features a highly effective mix of cellulose and lignin fibers. Balsa wood is therefore used in applications where light but strong structures are critical, from the blades in wind turbines to the chassis of model airplanes and helicopters. There is however a serious supply problem, in that over 95 percent of the world reserves of balsa wood comes from a single country – Ecuador.

Scientists at Harvard have now come up with a way to manufacture a cellular composite that’s even better than balsa wood, doing away with the occasional structural defects in the wood that can make it less reliable as a building material.

The researchers took inspiration from the microscopic structure of balsa, which is mostly hollow and in which only the cell walls are carrying the load. Their built their new composite using an epoxy-based resin containing nanoclay platelets to increase viscosity, as well as two types of fillers – silicon carbide “whiskers” and discrete carbon fibers.One very interesting feature is the fact that the researchers can control the exact stiffness of the material by changing the orientation of the fillers as needed. Orienting the silicon carbide whiskers perpendicularly to the direction which will face the most load makes the material stronger – for the same reason that it’s easier to chop wood longitudinally and not perpendicularly to its fibers.

This tunable property means that designers can digitally integrate into the composition the stiffness and toughness of an object from the very beginning, and have it comply with the desired specifications.

According to principal investigator Prof. Jennifer A. Lewis, their research is a significant step because it paves the way for 3D-printing using materials, such as epoxies, which can be used for structural applications, as opposed to the thermoplastics that your standard 3D printer uses. Using this resin, Lewis and colleagues obtained composites that are as stiff as wood, up to 20 times stiffer than commercial 3D-printed polymers, and twice as strong as the strongest printed polymer composites up to that point.

Applications for this technology could include more efficient wind turbines and perhaps innovative architecture for building lighter but safe cars that increase mileage.

A paper describing the advance appears in the journal Advanced Materials.

Below, you can watch a short clip of the composite being printed.

Source: Harvard University

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Smart morphing surfaces minimize drag at all speeds

Researchers at MIT have developed a smart curved surface that can morph at will to reduce drag, generating a series of small, evenly spaced dimples that make it resemble the outside of a golf ball. This technology could be used to reduce hurricane damage on some public buildings, as well as increase the aerodynamic and fuel efficiency in cars.

Scientists and golfers alike have long known that the dimples on the surface of a golf ball allow it to drastically reduce drag and travel much farther than would otherwise be possible. This happens because the small dents hold the airflow near the surface of ball for a longer time, and this reduces the size of the wake, or zone of turbulence, as the ball takes off.

In reality, though, things are a bit more complicated than that. In recent years, in-depth aerodynamic studies have shown that the dimples reduce drag only at lower speeds. As you move toward faster speeds, the advantage of irregularities disappears and a smooth surface becomes the best way to minimize the wake. That’s the reason why the Brazuca ball in use in this World Cup has dimples on its surface, but F1 cars don’t.

Now, researchers at MIT have married the best of both worlds by developing “smorphs,” smart morphing surfaces that can tune their smoothness on the fly to maximize aerodynamic efficiency at all speeds.

These new surfaces can change their configuration in real time because they’re made using a multilayer material with a stiff skin and a soft interior. When air is extracted from the interior of a small spherical object made out of this material, the surface shrinks slightly and its surface wrinkles, creating dimples at regular intervals that resemble, and have the same aerodynamic benefits as, golf balls.

The configuration of the material is controlled by adjusting the pressure inside the ball, and this means that the researchers can not only turn the dimples on and off, but also tune their size precisely to minimize drag for all speeds.

“Smorphs” could be especially useful in building structures that won’t collapse or incur significant damage when facing very high winds. One example could be the so-called radomes, the spherical, weatherproof domes that enclose radar antennas. The researchers say that the materials could also be used to minimize drag in cars in order to maximize fuel efficiency.

A paper published on the journal Advanced Materials describes the advance.

You can see a demonstration of a “smorph” surface in action in the video below.

Source: MIT

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Australian researchers simulate a time-traveling photon

Researchers at the University of Queensland, Australia claim to have simulated the behavior of a single photon traveling back in time and interacting with an older version of itself, in an effort to investigate how such a particle would behave. Their results suggest that, under such circumstances, the laws of quantum mechanics would stretch to become even more bizarre than they already are.

“General relativity seems to allow for so-called closed timelike curves (CTCs), paths in space-time that return to same point in space at an earlier time,” PhD student and lead author of the study Martin Ringbauer told Gizmag. “No CTC has been observed so far, but they appear in many solutions of Einstein’s field equations, which makes them an interesting object of study because traversing such a CTC would imply traveling backwards in time.”

The possibility of traveling back in time would open the door to inconsistencies in the classical world, such as the grandfather paradox: namely, if a time traveler were to prevent his own grandparents from meeting, he would also be preventing his own birth, which means he couldn’t have traveled back in time in the first place.

However, British physicist David Deutsch showed back in 1991 that while the grandfather paradox may be inescapable for macroscopic objects, the uncertainty principle that governs quantum particles such as photons leaves enough “wiggle room” to avoid such inconsistencies.

“An important aspect of classical objects is that they can only exist in a well defined state,” Ringbauer explained. “For the time traveler this means they either exist or don’t exist, which is at the heart of the grandfather paradox.”

“For quantum systems this is different, since they can exist in superpositions and mixtures of states,” he continued. “For the grandfather paradox, the corresponding quantum state of the time-traveler (now a photon) would be a mixture of existing and non-existing, which resolves the paradox and leads to a consistent evolution.”

The Australian researchers set out to study the consequences that Deutsch’s theory would have on the way quantum particles behave in a CTC. Specifically, the team studied how single photons would behave as they traversed a simulated CTC, traveled back in time, and then interacted with their older self. (The time-travel was simulated by using a second photon to play the part of the past incarnation of the time traveling photon.)

Such a system doesn’t give rise to time-traveling paradoxes. But the researchers did conclude that, in the presence of a closed time-like curve, the laws of quantum mechanics might change, giving rise to peculiar behaviors that are different to what standard quantum mechanics would predict.

In particular, such a quantum system might violate Heisenberg’s uncertainty principle, as it would be possible to perfectly distinguish the different states of a quantum system (which are usually only partially detectable).

This would make it possible to break quantum cryptography and perfectly clone quantum states. This, in turn, would lead to very dramatic speed increases in quantum computations – even beyond what they already promise compared to a classical computer.

The results do not have any implications for time-travel in the macroscopic case, and don’t answer the question of whether, how or why time travel might be possible in the quantum regime. However, they could help us understand the consequences of the existence of CTCs and provide insight into where and how nature might behave differently from what our theories currently predict.

The study appears in a recent issue of the journal Nature Communications.

Source: University of Queensland

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Conductive graphene yarn is lighter and stretchier than copper wire

Copper electrical wiring may soon be facing some stiff competition – or actually, some very stretchy competition. Scientists at Pennsylvania State University and Japan’s Shinshu University recently created a “super-stretchable” conductive yarn made from graphene.

The researchers started by chemically exfoliating flakes of graphene from a block of graphite. Those flakes were then mixed with water, and that mixture was concentrated into a slurry using a centrifuge. That slurry was then spread across a plate and allowed to dry, forming into a thin transparent film of graphene oxide.

The film was subsequently peeled off the plate and cut into narrow strips, those strips in turn getting wound together using an automatic fiber scroller.

The resulting yarn can be knotted and stretched without fracturing, and is said to be much stronger than other types of carbon fibers – this quality could be due to the presence of tiny air pockets within it.

Removing oxygen from the material boosts its electrical conductivity, and adding silver nanorods to it in the film-fabricating stage could reportedly boost that conductivity further, to the point of matching that of copper. Its stretchability and lighter weight, however, could make it a better alternative in many applications.

A paper on the research was recently published in the journal ACS Nano.

Source: Penn State

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New materials developed that are as light as aerogel, yet 10,000 times stronger

Imagine materials strong enough to use in building airplanes or motor cars, yet are literally lighter than air. Soon, that may not be so hard to do because a team of researchers from MIT and Lawrence Livermore National Laboratory (LLNL) have developed new ultra-lightweight materials that are as light as aerogel, but 10,000 times stiffer, and may one day revolutionize aerospace and automotive designs.

Aerogels are incredibly light, so light that the record holder, aerographene, boasts a density of just 0.16 mg/cm³. Currently, aerogels are used for insulation, tennis racquets, as a means of controlling oil spills, and were used on the NASA Stardust mission to collect samples from a comet’s tail. Unfortunately, despite its seemingly ephemeral nature, its very much a solid and will shatter if pressed hard enough, so its use is limited.

The new materials developed by the MIT/LLNL team aren’t aerogels, but are metamaterials. That is, artificial materials with properties that aren’t found in nature. The idea is to structure it, so that it has the lightness of aerogel, but is much stronger. The strength of the new materials comes from their geometric structure, not their chemical composition.

The new materials were made using projection micro-stereolithography, a form of desktop 3D printing that works on a microscopic level and can create highly complex, three-dimensional microstructures layer by layer very quickly for easy prototyping. It involves projecting a beam of ultraviolet light into a tank of polymers, responsive hydrogels, shape memory polymers, or bio-materials using the digital stereolithography technique in the form of masks, similar to those used to create microchips, to shape the layers.

Projection micro-stereolithography operates on a very small scale that allows the formation of “microlattices,” which are much like trusses and girders. Materials can even be switched during fabrication. According to the team, it can be applied to many different materials, including polymers, metals and ceramics, which is exactly what the team did using a variety of constituent materials.

Firstly, the LLNL/MIT team made a polymer template coated with a metal film 200 to 500 nanometers thick, then the polymer base was melted away, leaving behind the metal in the form of thin-film tubes.

The team then used the same technique but replaced the metal with ceramic to create ceramic tubes about 50 nanometers thick, which produced a material with the properties of an extremely stiff aerogel, four orders of magnitude stiffer than conventional aerogel, but with the same density.

The next step was to create a ceramic-polymer hybrid, which is a polymer with ceramic nanoparticles embedded into it. This relied on a slightly different process, with the polymer removed thermally, allowing the ceramic particles to densify into a solid. When the polymer was removed, the result was a stiff, ultralight ceramic solid instead of hollow tubes.

“These lightweight materials can withstand a load of at least 160,000 times their own weight,” said LLNL Engineer Xiaoyu “Rayne” Zheng. “The key to this ultrahigh stiffness is that all the micro-structural elements in this material are designed to be over constrained and do not bend under applied load.”

The team sees the materials as one day being used to develop parts and components for aircraft, motor cars, and space vehicles, and that in practical use, the material could end up being 100 times stronger than the experimental versions.

The research team’s results were published in the journal Science.

Sources: LNLL, MIT

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Three-dimensional light-sensitive retinal tissue grown in lab

The eye is often compared to a camera, but although its basic design is as simple as an old-fashioned box Brownie, its detailed structure is more complex than the most advanced electronics. This means that, unlike simpler organs, studies of retinal disease rely heavily on animal studies, and treating such illnesses is extremely difficult. One ray of hope in the field comes from researchers at Johns Hopkins, who have constructed a functioning segment of a human retina out of stem cells that is able to respond to light.

The retina is the complex lining of the human eye that acts like the the film (or the imaging sensor, for the younger crowd) in a camera. It’s made of some 10 layers of tissue, including structural membranes, nerve ganglia, and photoreceptor cells; the rods that detect black and white images and work best in low light, and the cones, which detect color. If scientists could recreate this structure in the laboratory, it would be a major breakthrough in treating eye diseases.

The Johns Hopkins researchers’ approach was to use human-induced pluripotent stem cells (iPS). In other words, adult cells were induced to revert to stem cells, from which any of the 200 specialized cells in the human body can be derived. The Johns Hopkins team programmed the stem cells to grow into retinal progenitor cells in a culture dish.

These cells developed into retina cells, much in the same way and at the same rate as in a human embryo. As they did so, the cells differentiated into the some of the seven different kinds of cells that make up the retina and organized themselves into the three-dimensional outer segment structures necessary for the photoreceptors to work.

“We knew that a 3D cellular structure was necessary if we wanted to reproduce functional characteristics of the retina,” says M Valeria Canto-Soler, an assistant professor of ophthalmology at the Johns Hopkins University School of Medicine, “but when we began this work, we didn’t think stem cells would be able to build up a retina almost on their own. In our system, somehow the cells knew what to do.”

Growing retina segments has been achieved before, but where Johns Hopkins’ work stands out is that these mini-retinas actually function. When the mini-retinas reached the equivalent of 28-weeks of development, the researchers hooked the photoreceptor cells up to electrodes and flashed pulses of light at them. According to the scientists, the cells displayed the same photochemical reactions as in a normal retina – especially in regard to the rods that make up the majority of the photoreceptors.

The result of the Johns Hopkins research is a mini-retina that responds to light, but doesn’t have the ability to form images. The structure is nowhere near complete and there’s no way to connect the artificial retina to the brain’s visual cortex. However, being able to produce retinal structures of such complexity holds the promise of developing new ways of studying eye diseases and developing new ways to treat them.

According to Cano-Soler, the technique will allow doctors to grow hundreds of mini-retina from a patient’s own cells, allowing for advanced testing and individualized drug treatments. In addition, it will allow scientists to study eye diseases without animal tests. Eventually, it may even lead to a means of restoring vision in patients with retinal diseases with transplants of lab-grown retinas.

The team’s results were published in the journal Nature Communications.

Source: Johns Hopkins

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LLNL improving the efficiency of 3D metal printing

To paraphrase Samuel Johnson, there was a time when 3D metal printing was like a dog walking on his hind legs – it wasn’t done well; but you were surprised to find it done at all. Now that laser sintering or Selective Laser Melting (SLM) is used for everything from printing rocket engine components to semi-automatic pistols, the time for surprise may b long past, but the technology still has plenty of room for improvement. That’s why researchers at the Lawrence Livermore National Laboratory (LLNL) are working on simulations to improve the speed of 3D laser printing and the quality of the final product by using higher-powered lasers.

SLM is a form of additive printing where, instead of squirting melted plastic out like cake icing, an object is built up layer by layer using metal powder that’s melted into a pool by a high-power laser. As each layer is fused into the desired shape, the printer adds another layer of powder and the process repeats until the printing is completed. Then, you remove the excess powder, give the printed object a polish, and you’re done.

The problem is that 3D printing is rapidly developing from a novelty into a mainstream manufacturing technique. That means that processes like SLM need to improve quickly in terms of predictability, quality, and speed of output. In the case of SLM, a key question is how to get the resulting metal as close as possible to full density in as short a time as possible.

This is where the LLNL study has concentrated its efforts. Currently, laser printing works best when the laser is kept below 225 W. The researchers wanted to figure out how to get the same results with lasers in the 400 W range, but that meant dealing with a wide range of factors, such as laser power, laser speed, the distance between laser scan lines, the scanning strategy, and powder layer thickness.

Since SLM works by melting powders, porosity was a major problem. If the grains of powder don’t melt properly, the metal, in this case 315L stainless steel, becomes porous, and therefore weaker. For many applications, engineers require porosity of less than 1 percent, but that means balancing the various factors.

To achieve this balance, LLNL is developing computer models that predict the optimum balance of the various parameters for the fastest and most cost-effective way of carrying out a particular high-density printing process.

“We mine the simulation output to identify important SLM parameters and their values such that the resulting melt pools are just deep enough to melt through the powder into the substrate below,” says Chandrika Kamath, an LLNL researcher. “By using the simulations to guide a small number of single-track experiments, we can quickly arrive at parameter values that will likely result in high-density parts.”

“We found that the metal density reduces if the speed is too low, due to voids created as a result of keyhole mode laser melting, where the laser drills into the material,” added Kamath. “At the same time, too high a speed results in insufficient melting. The key is to find the right parameters where the melting is just enough.”

One result that’s of particular interest is that the team learned that using higher power provided a more consistently high density material for a wide range of metal powders, while lower powers had a greater range of porosity. According to the team, the simulations will be helpful in understanding the process parameters and certifying the properties of printed metal parts.

The teams results were published in the International Journal of Advanced Manufacturing Technology.

Source: Lawrence Livermore National Laboratory

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The Milky Way may host over 100 million planets supporting complex life

A survey conducted by astronomers at Cornell University has taken into account the characteristics of 637 known exoplanets and elaborated a Biological Complexity Index (BCI) to assess the relative probability of finding complex life on them. Their data supports the view that as many as one hundred million planets scattered around the Milky Way, and perhaps more, could support life beyond the microbial stage.

The Biological Complexity Index

We know that organic molecules are present in star-forming regions, protoplanetary disks, meteorites, comets, and even deep space; moreover, water is among the most common molecules in the Universe, and energy is available in many forms both on the surface and deep within a planet. These reasons lead us to believe that may be other forms of life even within our galaxy; however, the question of just how many might be there has been a topic of speculation for decades.

In 1961, American astronomer Frank Drake proposed a formula that could be used to roughly estimate of the number of intelligent and technologically advanced extraterrestrial civilizations in the Milky Way. However, we have so little data on the world outside our solar system that estimating the parameters of this formula accurately is next to impossible. Depending on your initial assumptions, the number of advanced civilizations in our galaxy according to Drake’s equation could range from virtually zero to a whopping 36.4 million.

Now, a group of scientists at Cornell University led by associate professor Alberto Fairén have proposed a formula that takes into account the characteristics of over 600 known exoplanets to help estimate how likely we are to find complex life on them. By “complex life,” the researchers don’t mean necessarily technologically advanced or even highly intelligent life, but rather life forms that are above the microbial level and form stable food chains like those found in ecosystems on Earth.

The researchers took into account the density, temperature, substrate, chemistry, distance from its star and age of a given exoplanet, combining these parameters into a unique metric that they call the Biological Complexity Index (BCI).

The BCI can use the limited information in our possession to assess the relative likelihood of different planets to host complex life (Image: Cornell University)

The index doesn’t represent an absolute statistical prediction of whether complex life could be present on a planet; rather, it can be used to estimate the relative likelihood of life having evolved there, based on the conditions that we know are compatible with the evolution of complex life forms on a planet, and assuming that no further information is available.

In essence, an outside observer could use the index to compare two planets or moons which are light-years away and with only limited, easily detectable information at his disposal, tell which one is the most likely to harbor life.

Life on other planets

Prof. Fairén and colleagues have used the BCI index to assess the habitability of 637 known exoplanets for which they had access to all the necessary parameters. According to their report, 11 of those exoplanets (1.7 percent of the sample) have a BCI above that of Europa, and five (0.8 percent of sample) have a score higher than Mars. Although that number might seem small, when extrapolating it to the entire galaxy this means there may be north of 100 million planets in our Milky Way alone on which complex life has plausibly evolved.

Of course, the accuracy of this estimation is constrained by the limited amount of data that we have on those planets. For instance, our instruments aren’t currently powerful enough to detect Earth-size planets that are very far away, and this might mean that the estimate is actually a conservative one. On the other hand, some planets that might look hospitable from light-years away may not look as good after a closer look.

According to some astronomers, worlds that are larger, warmer, and older than Earth, orbiting dwarf stars, are probably the most likely candidates for hosting complex life. The results from Fairén team’s survey are in accordance with this theory, as all five exoplanets detected with a BCI value higher than Mars have exactly these characteristics.

Curiously enough one of the planets, Gliese 581c, has an even higher BCI value than Earth. Again, this is not a comment on the absolute likelihood of finding complex life there; rather, it means that if an external observer (such as a technically advanced alien civilization) were to observe both Earth and Gliese 581c from light-years away, with only limited information at their disposal, they might be led to conclude that Gliese 581c is the more likely candidate for hosting life – at least, if they were using the same formula.

The Biological Complexity Index plotted against the Earth Similarity Index (Image: Cornell University)

We know quite well from looking at the fossil record that life appeared on Earth very soon after the environmental conditions were favorable on the surface. Therefore, a further refinement might be to combine the BCI with a second metric that takes into account how similar a planet is compared to Earth. The researchers have therefore proposed an “Earth Similarity Index” (ESI) rates the similarity of extrasolar planets to Earth on the basis of mass, size, and temperature.

Overall, the data produced by the researchers supports the idea that the evolution of complex life on other worlds is relatively rare across our galaxy, but still extremely large in terms of absolute numbers. So, even though they may very well be countless other advanced forms of life in the Milky Way, we are so far from one another that we are unlikely to make the trip there in the foreseeable future.

When the James Webb Space Telescope – an instrument so powerful that it could easily detect a firefly from a distance of 240 thousand miles (385,000 km) – launches in 2018, we will be able to gather much more accurate data on which to base our estimations.

The researchers describe their findings in an open-access paper published on the journal Challenges.

Source: Cornell University

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Biodegradable fibers as strong as steel made from wood cellulose

A team of researchers working at Stockholm’s KTH Royal Institute of Technology claim to have developed a way to make cellulose fibers stronger than steel on a strength-to-weight basis. In what is touted as a world first, the team from the institute’s Wallenberg Wood Science Center claim that the new fiber could be used as a biodegradable replacement for many filament materials made today from imperishable substances such as fiberglass, plastic, and metal. And all this from a substance that requires only water, wood cellulose, and common table salt to create it.

To produce the new material, the team took individual cellulose fibers and broke them down into their component strands or “fibrils.” They then separated and re-bound these fibrils in a technique that results in filaments much stronger than the original fiber. While fibrils have been separated in other studies – and even used in strengthening composite materials – it is the recombining of these fibrils into a super-strong filament that has never been achieved before and is asserted to be a considerable breakthrough in this type of research.

“We have taken out fibrils from natural cellulose fibers, then we have assembled fibrils again into very strong filament,” said Fredrik Lundell, one of the researchers. “It is about 10 to 20 microns thick, much like a strand of hair.”

The team constructed a “flow-focusing” device (similar to a small-scale extruder) to reassemble the fibrils after they had been mixed with water and sodium chloride. Controlling their reassembly by carefully adjusting the pressure at which they were injected, the researchers were able to produce continuous, consistent strands of fiber from the fibrils.

In this process, the way that they manipulate the angle at which the fibrils are brought together then determines the strength and stiffness of that fiber. For example, if the fibrils are aligned alongside each other, the material is rigid and inflexible, whereas if the fibrils are combined at angles to each other, the resulting material is more elastic and flexible.

The useful upshot of this is that the fibrils can be used to produce not only strong, steel-like fibers, but more fibrous ones as well. As a result, wood cellulose could be made to replace cotton in textiles, or even be used as a substitute for the glass filaments used in fiberglass used to construct boats and cars. And, as the new material retains its original cellulose, it is still biodegradable just like the wood it came from.

“Our research may lead to a new construction material that can be used anywhere where you have components based on glass fibers, and there are quite a few places,” said Lundell. “The challenge we face now is to scale up the production process. We must be able to make long strands, many threads in parallel – and all this much faster than today. Nevertheless, we have demonstrated that we know how this should be done, so we’ve come a long way.”

The work was carried out in cooperation with Deutsches Elektronen-Synchrotron elektronsynkrotronen (DESY) in Hamburg, Germany, with the research findings published in the scientific journal Nature Communications.

Photos: KTH

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Copper nanowire coating could lead to shatterproof smartphone screens

Chances are that the touchscreen on your smartphone or tablet incorporates a coating of indium tin oxide, also known as ITO or tin-doped indium oxide. Although it’s electrically conductive and optically transparent, it’s also brittle and thus easily-shattered. Scientists at Ohio’s University of Akron, however, are developing something that could ultimately replace the material. They’ve created an electrode coating that’s not only as transparent and more conductive than ITO, but is also far tougher.

The coating, developed by a team led by assistant professor of polymer science Yu Zhu, is comprised of a network of linked copper nanowires. It can be deposited on either rigid glass or flexible clear polymer sheets.

To make it, the researchers start by depositing a copper film on the transparent substrate. Nanofibers made from a polymer known as polyacrylonitrile (PAN) are then electrospun onto that film. In order to get those fibers good and flattened-down against the film, a solvent annealing (heating and cooling) process is subsequently conducted.

Next, the coated sheet is immersed in a metal-etching solution, which removes all of the copper not protectively masked by the PAN fibers. Finally, those fibers are themselves removed, using an organic solvent that doesn’t affect the copper. What’s left is the glass or polymer sheet, covered in a clear layer of interconnected copper nanowires where the nanofibers shielded the film.

Sheets of transparent polymer that received the treatment retained their conductive qualities after Scotch tape had been repeatedly applied to and peeled off of the coating, and after they were bent up to 1,000 times. Because of that flexibility, it should be possible to economically mass-produce polymer touchscreens treated with the coating, in roll form.

Although other institutions have developed graphene-based transparent electrode coatings that are likewise tougher than ITO, the U Akron coating is reportedly less costly to produce. Additionally, it is produced right on the substrate, whereas graphene has to be created separately and then painstakingly transferred across (although that might not be the case formuch longer).

Other nanowire-based electrode coatings have also previously been created. According to the university, however, those fall behind Zhu’s approach when it comes to adhesion, smoothness, and/or conductivity.

“We expect this film to emerge on the market as a true ITO competitor,” he said. “The annoying problem of cracked smartphone screens may be solved once and for all with this flexible touchscreen.”

A paper on the research was recently published in the journal ACS Nano.

Source: The University of Akron

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