Ready for an unscratchable phone screen? Sapphire is coming | Digital Trends

By Jeffrey Van Camp — February 27, 2013

Earlier this month, a study showed that 23 percent of iPhone users have screens that are currently broken, and the average person has put up with their broken screen for six months. We can argue about the numbers all day, but chances are almost all of you are afraid of breaking your device screen. Drop your phone from just a few feet and you’re done. It’s over. Your screen has broke. Can you fix it? How do you fix it? Who do you contact? How much will it cost? These are the kind of questions that can ruin your day, your week, your month, or even your year.

We all carry around a smartphone and they’re all covered in highly breakable glass. Sometimes its soda-lime glass and sometimes its made of fancy Gorilla Glass, but even the best screens are still very easy to crack, break, and shatter. It’s no fun, but it may soon be a thing of the past. At Mobile World Congress, I stumbled upon one of the coolest new tech innovations in a very long time. And guess what? It’s as old as the earth itself.

GT Advanced Technologies is a company that manufacturers furnaces that melt down sapphire, and is at MWC this year to tell everyone that the sapphire industry is getting into the gadget screen business in a big way. Your next iPhone or Android device may very well have a sapphire screen. And it could save you a trip to some shady guy’s basement to fix your screen.

“Gorilla Glass is still glass, so the way that you break glass is that you score it, and then it breaks. So when you scratch your mobile phone, that’s why when you drop your mobile phone it breaks – because there are scratches in it,” Dan Squiller of GT Advanced told us as he let us scratch up a Gorilla Glass screen with a rock. “So, with sapphire, because you cannot scratch it, it doesn’t break. So if you drop your phone, or abuse it, it won’t break. It’s very very rugged. It won’t scratch; it won’t break … You could throw this phone against a cement wall and it won’t break … well, the phone might break, but the screen will stay intact.”

I was easily able to scratch the Gorilla Glass, and shatter it, but couldn’t make a mark on the sapphire. GT Advanced claims that its sapphire is about three times stronger than most chemically strengthened aluminosilicate glass, including Gorilla Glass, Dragontrail glass, soda-lime glass, and Xensation glass.

(I found Corning, maker of Gorilla Glass, at the show this week, but it had no representatives available for comment on how its glass compares to sapphire.)

GT Advanced demonstrations were compelling, and the science seems to back it up. Sapphire is a naturally growing crystal and is the second hardest substance on earth. It’s so hard, only diamond-tipped saws can cut it. GT Advanced grows sapphire and then melts and hardens them into ‘boules,’ which are 115 kilogram, or 254 lb. clear cylinders. Those cylinders are then cut into cubes, which are then chopped up into slices and shapes as thin and wild as you can imagine.

Sapphire can be made as clear as glass and as thin as you desire, and is the perfect material for a phone or tablet screen because almost nothing can scratch it. The crystal is regularly used in things like jewelry, watches, military windshields, LED TVs, and LED light bulbs, but the sapphire industry is a few years late to the game when it comes to mobile touchscreens.

“We’ve only just mounted the effort to sell it into the mobile space,” said Squiller. “We have won contracts with point-of-sale people like Motorola; they’ll be using it in their point-of-sale scanners. We didn’t realize what we had here, but the mobile industry has a huge problem with broken screens. You wouldn’t believe the number of people who come by the booth and take out their phone and show us their shattered phone.”

Right now, the only phone that uses a full sapphire screen is the Vertu TI, an $11,000 Android device . This is partially because of price: A sapphire screen costs a phone manufacturer about three times more than a Gorilla Glass screen, but GT Advanced doesn’t believe cost will be a barrier. Apple’s iPhone 5 uses a sapphire lens for its rear camera.

“Based on the conversations we’ve had with OEMS [Original Equipment Manufacturers], they’re willing to pay up to $15 or $20 for a better screen,” explained Squiller. “This will be $10 to $15 more expensive than Gorilla Glass. I think that [Gorilla Glass] display – that display that you just ruined – I think that was about $5 or $6 and we’re going to be at about $15 or so.”

But even if it takes a while to get phone and tablet makers like Apple and Samsung onboard, you won’t have to wait too long. Squiller already showed us prototype sapphire iPhone 5 screen protectors and replacement screens that will add next to no bulk to your device, and be available for anyone to buy “next year at this time,” or early 2014.

There are plenty of ways phones need to improve their durability in the years to come, but if sapphire screens take off, we might be able to scratch broken screens off the list. Or, then again, if today’s demonstration was any indication, maybe we won’t.

(Photos by Ben Nelson, Envision Studio )

Stanford University Researchers Make Complex Carbon Nanotube Circuits | MIT Technology Review

Carbon nanotubes could help make computers faster and more efficient—if they can be incorporated into complex circuits.

Carbon complexity: This wafer is patterned with a complex carbon nanotube circuit that serves as a sensor interface.

Researchers at Stanford University have built one of the most complex circuits from carbon nanotubes yet. They showed off a simple hand-shaking robot with a sensor-interface circuit last week at the International Solid-State Circuits Conference in San Francisco.

As the silicon transistors inside today’s computers reach their physical limits, the semiconductor industry is eyeing alternatives, and one of the most promising is carbon nanotubes. Tiny transistors made from these nanomaterials are faster and more energy efficient than silicon ones, and computer models predict that carbon nanotube processors could be an order of magnitude less power hungry. But it’s proved difficult to turn individual transistors into complex working circuits (see “How to Build a Nano-Computer ”).

The demonstration carbon nanotube circuit converts an analog signal from a capacitor—the same type of sensor found in many touch screens—into a digital signal that’s comprehensible by a microprocessor. The Stanford researchers rigged a wooden mannequin hand with the capacitive switch in its palm. When someone graspsed the hand, turning on the switch, the nanotube circuit sent its signal to the computer, which activated a motor on the robot hand, moving it up and down to shake the person’s hand.

Other researchers have demonstrated simple nanotube circuits before, but this is the most complex made so far, and it also demonstrates that nanotube transistors can be made at high yields, says Subhasish Mitra , an associate professor of electrical engineering and computer science, who led the work with Philip Wong , a professor of electrical engineering at Stanford.

The nanotube circuit is still relatively slow—its transistors are large and far apart compared to the latest silicon circuits. But the work is an important experimental demonstration of the potential of carbon nanotube computing technology.

“This shows that carbon nanotube transistors can be integrated into logic circuits that perform at low voltage,” says Aaron Franklin , who is developing nanotube electronics at the IBM Watson Research Center. This feat has been demonstrated by Franklin’s group at the single-transistor level, and been shown to be theoretically possible by others, but seeing it in a complex circuit is important, says Franklin.

Working with carbon nanotubes presents many challenges—as many as 30 percent of them are metallic, rather than semiconducting, with the potential to burn out a circuit. Nanotubes also tend to grow in a spaghetti-like tangle, which can cause circuits to switch unpredictably. The approach taken by the Stanford group is to work with their imperfections, coming up with error-tolerant circuit design techniques that allow them to build circuits that work even when the starting materials are flawed. “We want to build up the circuit complexity, then go back to improving the building methods, then make more complex circuits,” says Wong.

“This is no different from the early days in silicon,” says Ashraf Alam , professor of electrical and computer engineering at Purdue University. Compared to the electronics in today’s silicon-based smartphones and supercomputers, the first silicon transistors were poor quality, as were the first integrated circuits. But silicon got through its growing pains, and the semiconductor industry perfected building ever-denser arrays of integrated circuits made up of ever-smaller transistors.

“Variation and imperfection are going to be the air we breathe in semiconductor technology,” says Wong, not just for those working with new materials, but for conventional silicon technology, too. Today’s state-of-the-art chips use 22-nanometer transistors—billions on each chip—and there is very little variation in their performance; the semiconductor industry has mastered making these tiny devices at tremendous scales, and with very high yields.

The drive to continually miniaturize transistors while maintaining scrupulous quality control has enabled technologies ranging from smartphones and supercomputers. But unavoidable flaws, at the level of single atoms, will soon lead to variation in performance that will have to be accounted for in circuit design. “Error-tolerant design has to be part of the way forward, because we will never get the materials completely perfect,” says Wong.

Scientists develop a whole new way of harvesting energy from the sun

Feb. 24, 2013 — A new method of harvesting the Sun’s energy is emerging, thanks to scientists at UC Santa Barbara’s Departments of Chemistry, Chemical Engineering, and Materials. Though still in its infancy, the research promises to convert sunlight into energy using a process based on metals that are more robust than many of the semiconductors used in conventional methods.

The researchers’ findings are published in the latest issue of the journal Nature Nanotechnology.

“It is the first radically new and potentially workable alternative to semiconductor-based solar conversion devices to be developed in the past 70 years or so,” said Martin Moskovits, professor of chemistry at UCSB.

In conventional photoprocesses, a technology developed and used over the last century, sunlight hits the surface of semiconductor material, one side of which is electron-rich, while the other side is not. The photon, or light particle, excites the electrons, causing them to leave their postions, and create positively-charged “holes.” The result is a current of charged particles that can be captured and delivered for various uses, including powering lightbulbs, charging batteries, or facilitating chemical reactions.

“For example, the electrons might cause hydrogen ions in water to be converted into hydrogen, a fuel, while the holes produce oxygen,” said Moskovits.

In the technology developed by Moskovits and his team, it is not semiconductor materials that provide the electrons and venue for the conversion of solar energy, but nanostructured metals — a “forest” of gold nanorods, to be specific.

For this experiment, gold nanorods were capped with a layer of crystalline titanium dioxide decorated with platinum nanoparticles, and set in water. A cobalt-based oxidation catalyst was deposited on the lower portion of the array.

“When nanostructures, such as nanorods, of certain metals are exposed to visible light, the conduction electrons of the metal can be caused to oscillate collectively, absorbing a great deal of the light,” said Moskovits. “This excitation is called a surface plasmon.”

As the “hot” electrons in these plasmonic waves are excited by light particles, some travel up the nanorod, through a filter layer of crystalline titanium dioxide, and are captured by platinum particles. This causes the reaction that splits hydrogen ions from the bond that forms water. Meanwhile, the holes left behind by the excited electrons head toward the cobalt-based catalyst on the lower part of the rod to form oxygen.

According to the study, hydrogen production was clearly observable after about two hours. Additionally, the nanorods were not subject to the photocorrosion that often causes traditional semiconductor material to fail in minutes.

“The device operated with no hint of failure for many weeks,” Moskovits said.

The plasmonic method of splitting water is currently less efficient and more costly than conventional photoprocesses, but if the last century of photovoltaic technology has shown anything, it is that continued research will improve on the cost and efficiency of this new method — and likely in far less time than it took for the semiconductor-based technology, said Moskovits.

“Despite the recentness of the discovery, we have already attained ‘respectable’ efficiencies. More importantly, we can imagine achievable strategies for improving the efficiencies radically,” he said.

Research in this study was also performed by postdoctoral researchers Syed Mubeen and Joun Lee; grad student Nirala Singh; materials engineer Stephan Kraemer; and chemistry professor Galen Stucky.

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Scientists find weird new property of matter that breaks all the rules | The Verge

Similar eureka moments have brought us maglev trains — what’s next?

By Arikia Millikan on February 18, 2013 06:55 pm Email 156Comments

Don’t miss any stories Follow The Verge

When physicists discover new properties of matter, it usually means better technologies for the rest of us. Superconductors, liquid crystal displays like the ones found in most TVs now, medical imaging technologies that allow doctors to peer inside the human body, and magnetic levitation — which was used to create the Shanghai Maglev train — are all examples of how discoveries of new properties of matter have resulted in revolutionary products.

A quantum dot energy harvester

An array on nano energy harvesters in what the researchers call a “swiss cheese” arrangement. (Credit: Image courtesy of University of Rochester)

Feb. 14, 2013 — A new type of nanoscale engine has been proposed that would use quantum dots to generate electricity from waste heat, potentially making microcircuits more efficient.

“The system is really a simple one, which exploits certain properties of quantum dots to harvest heat,” Professor Andrew Jordan of the University of Rochester said. “Despite this simplicity, the power it could generate is still larger than any other nanoengine that has been considered until now.”

The engines would be microscopic in size, and have no moving parts. Each would only produce a tiny amount of power — a millionth or less of what a light bulb uses. But by combining millions of the engines in a layered structure, Jordan says a device that was a square inch in area could produce about a watt of power for every one degree difference in temperature. Enough of them could make a notable difference in the energy consumption of a computer.

A paper describing the new work is being published in Physical Review B by Jordan, a theoretical physics professor, and his collaborators, Björn Sothmann and Markus Buttiker from the University of Geneva, and Rafael Sánchez from the Material Sciences Institute in Madrid.

Jordan explained that each of the proposed nanoengines is based on two adjacent quantum dots, with current flowing through one and then the other. Quantum dots are manufactured systems that due to their small size act as quantum mechanical objects, or artificial atoms.

The path the electrons have to take across both quantum dots can be adjusted to have an uphill slope. To make it up this (electrical) hill, electrons need energy. They take the energy from the middle of the region, which is kept hot, and use this energy to come out the other side, higher up the hill. This removes heat from where it is being generated and converts it into electrical power with a high efficiency.

To do this, the system makes use of a quantum mechanical effect called resonant tunneling, which means the quantum dots act as perfect energy filters. When the system is in the resonant tunneling mode, electrons can only pass through the quantum dots when they have a specific energy that can be adjusted. All other electrons that do not have this energy are blocked.

Quantum dots can be grown in a self-assembling way out of semiconductor materials. This allows for a practical way to produce many of these tiny engines as part of a larger array, and in multiple layers, which the authors refer to as the Swiss Cheese Sandwich configuration (see image).

How much electrical power is produced depends on the temperature difference across the energy harvester — the higher the temperature difference, the higher the power that will be generated. This requires good insulation between the hot and cold regions, Jordan says.

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New order found in quantum electronic material: May lead to new materials, magnets and superconductors

High-speed train. Two Rutgers physics professors have proposed an explanation for a new type of order, or symmetry, in an exotic material made with uranium — a theory that may one day lead to enhanced computer displays and data storage systems and more powerful superconducting magnets for medical imaging and levitating high-speed trains. (Credit: © Daniel Loncarevic / Fotolia)

Jan. 30, 2013 — Two Rutgers physics professors have proposed an explanation for a new type of order, or symmetry, in an exotic material made with uranium — a theory that may one day lead to enhanced computer displays and data storage systems and more powerful superconducting magnets for medical imaging and levitating high-speed trains.

Their discovery, published in this week’s issue of the journal Nature, has piqued the interest of scientists worldwide. It is one of the rare theory-only papers that this selective publication accepts.

Collaborating with the Rutgers professors was a postdoctoral researcher at Massachusetts Institute of Technology (MIT) who earned her doctorate at Rutgers.

“Scientists have seen this behavior for 25 years, but it has eluded explanation.” said Piers Coleman, professor in the Department of Physics and Astronomy in the School of Arts and Sciences. When cooled to 17.5 degrees above absolute zero or lower (a bone-chilling minus 428 degrees Fahrenheit), the flow of electricity through this material changes subtly.

The material essentially acts like an electronic version of polarized sunglasses, he explains. Electrons behave like tiny magnets, and normally these magnets can point in any direction. But when they flow through this cooled material, they come out with their magnetic fields aligned with the material’s main crystal axis.

This effect, claims Coleman, comes from a new type of hidden order, or symmetry, in this material’s magnetic and electronic properties. Changes in order are what make liquid crystals, magnetic materials and superconductors work and perform useful functions.

“Our quest to understand new types of order is a vital part of understanding how materials can be developed to benefit the world around us,” he said.

Similar discoveries have led to technologies such as liquid crystal displays, which are now ubiquitous in flat-screen TVs, computers and smart phones, although the scientists are quick to acknowledge that their theoretical discovery won’t transform high-tech products overnight.

Coleman, along with Rutgers colleague Premala Chandra and MIT collaborator Rebecca Flint, describe what they call a “hidden order” in this compound of uranium, ruthenium and silicon. Uranium is commonly known for being nuclear reactor fuel or weapons material, but in this case physicists value it as a heavy metal with electrons that behave differently than those in common metals.

Recent experiments on the material at the National High Magnetic Field Laboratory at Los Alamos National Laboratory in New Mexico provided the three physicists with data to refine their discovery.

“We’ve dubbed our fundamental new order ‘hastatic’ order, named after the Greek word for spear,” said Chandra, also a professor in the Department of Physics and Astronomy. The name reflects the highly ordered properties of the material and its effect on aligning electrons that flow through it.

“This new category of order may open the world to new kinds of materials, magnets, superconductors and states of matter with properties yet unknown,” she said. The scientists have predicted other instances where hastatic order may show up, and physicists are beginning to test for it.

The scientists’ work was funded by the National Science Foundation and the Simons Foundation. Flint is a Simons Postdoctoral Fellow in physics at MIT.

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Mysteries of spider silk strength unraveled

Female Nephila clavipes on her web. The web was characterized using Brillouin spectroscopy to directly and non-invasively determine the mechanical properties. (Credit: Jeffery Yarger)

Jan. 27, 2013 — Scientists at ASU are celebrating their recent success on the path to understanding what makes the fiber that spiders spin — weight for weight — at least five times as strong as piano wire. They have found a way to obtain a wide variety of elastic properties of the silk of several intact spiders’ webs using a sophisticated but non-invasive laser light scattering technique.

“Spider silk has a unique combination of mechanical strength and elasticity that make it one of the toughest materials we know,” said Professor Jeffery Yarger of ASU’s Department of Chemistry and Biochemistry, and lead researcher of the study. “This work represents the most complete understanding we have of the underlying mechanical properties of spider silks.”

Spider silk is an exceptional biological polymer, related to collagen (the stuff of skin and bones) but much more complex in its structure. The ASU team of chemists is studying its molecular structure in an effort to produce materials ranging from bulletproof vests to artificial tendons.

The extensive array of elastic and mechanical properties of spider silks in situ, obtained by the ASU team, is the first of its kind and will greatly facilitate future modeling efforts aimed at understanding the interplay of the mechanical properties and the molecular structure of silk used to produce spider webs.

The team published their results in a recent issue of Nature materials and their paper is titled “Non-invasive determination of the complete elastic moduli of spider silks.”

“This information should help provide a blueprint for structural engineering of an abundant array of bio-inspired materials, such as precise materials engineering of synthetic fibers to create stronger, stretchier, and more elastic materials,” explained Yarger.

Other members of Yarger’s team, in ASU’s College of Liberal Arts and Sciences, included Kristie Koski, at the time a postdoctoral researcher and currently a postdoctoral fellow at Stanford University, and ASU undergraduate students Paul Akhenblit and Keri McKiernan.

The Brillouin light scattering technique used an extremely low power laser, less than 3.5 milliwatts, which is significantly less than the average laser pointer. Recording what happened to this laser beam as it passed through the intact spider webs enabled the researchers to spatially map the elastic stiffnesses of each web without deforming or disrupting it. This non-invasive, non-contact measurement produced findings showing variations among discrete fibers, junctions and glue spots.

Four different types of spider’s webs were studied. They included Nephila clavipes (pictured), A. aurantia (“gilded silver face”-common to the contiguous United States), L. Hesperus the western black widow and P. viridans the green lynx spider, the only spider included that does not build a web for catching prey but has major silk elastic properties similar to those of the other species studied.

The group also investigated one of the most studied aspects of orb-weaving dragline spider silk, namely supercontraction, a property unique to silk. Spider silk takes up water when exposed to high humidity. Absorbed water leads to shrinkage in an unrestrained fiber up to 50 percent shrinkage with 100 percent humidity in N. clavipes silk.

Their results are consistent with the hypothesis that supercontraction helps the spider tailor the properties of the silk during spinning. This type of behavior, specifically adjusting mechanical properties by simply adjusting water content, is inspirational from a bio-inspired mechanical structure perspective.

“This study is unique in that we can extract all the elastic properties of spider silk that cannot and have not been measured with conventional testing,” concluded Yarger.

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Monster Wind Turbine Blades Could Help Offshore Wind Compete with Fossil Fuels | MIT Technology Review

Offshore wind is a huge resource, but it can’t yet compete with fossil fuels.

Big blade: The forms for the 80-meter turbine blades that Vestas is developing stretch into the distance.

Blade Dynamics, a six-year-old company that’s partly owned by American Semiconductor, a wind turbine designer and supplier of wind farm electronics, says that it has developed technology that will make possible the world’s largest wind turbine blades. It’s demonstrated the technology by manufacturing 49-meter blades, and now the Energy Technologies Institute, a partnership between the U.K. government and major corporations such as BP, Shell, and Caterpillar, has given the company nearly $25 million to build 100-meter blades. They could enable 250-meter-tall wind turbines that would tower over the Washington Monument, which stands a mere 169 meters tall. The largest wind turbine blades now are 75 meters long (see “A Mighty Wind Turbine ”).

The effort is no mere record-setting spectacle. Finding affordable ways to make the enormous wind turbine blades is one of the biggest challenges to making offshore wind competitive with fossil fuels, and leading wind power companies, including GE and Vestas, are developing technology to solve the problem.

Some of the best winds for generating power are found offshore, where wind can be steadier, faster, and less turbulent than on land. Wind turbines only make up about a third of the cost of offshore wind farms—installation costs are the major expense, as they involve enormous, specialized ships and are subject to delays from bad weather. Using larger wind turbines reduces the number of wind turbines needed, decreasing installation and maintenance costs (see “Building Bigger, Better Wind Turbines ” and “The Great German Energy Experiment ”).

One problem with building very large wind turbines is that the cost of making the blades is skyrocketing. As wind turbines get bigger, the loads on the blades, and therefore their weight, goes up exponentially. The conventional way for making blades involves forms that are as long as the blades themselves. The forms and other equipment needed to make them are becoming so big and specialized that there are few suppliers, which increases prices for manufacturing equipment. Making sure the blades are formed accurately also gets more and more difficult as blades get longer.

Some major wind turbine manufacturers are sticking with the large forms, but are adopting carbon-reinforced fiberglass blades and new blade designs to offset some of the manufacturing cost increase. They’re also counting on savings in installation and other costs to make the business case for larger wind turbines. Siemens, for example, is using large forms for its 75-meter blades, as is Vestas, which is developing 80-meter blades for a wind turbine that will be available next year.

While manufacturers like Vestas are using carbon-reinforced blades, Blade Dynamics is making blades entirely out of carbon fiber. The company has developed proprietary ways to make 12- to 20-meter sections of carbon fiber blade and then splice them together seamlessly—eliminating the need for large forms. Some previous attempts at modular blades involved bolting blade sections together, but this created stress points within the blades that make them too weak.

Carbon fiber is more expensive than fiberglass, so for a given length, the blades will be more expensive. But David Cripps, senior technical manager at Blade Dynamics, says the use of carbon fiber can improve the overall economics of wind turbines in several ways. By making the blade in smaller sections, it’s possible to make more precise aerodynamic structures, improving performance, he says. Also, because the blades weigh much less than fiberglass ones, it’s possible to put longer blades on existing wind turbine designs. For example, the company’s 49-meter blade weighs no more than a conventional 45-meter blade specified by a wind turbine’s original design. Longer blades gather more wind, allowing the turbines to generate more power at lower wind speeds, increasing revenue.

The lighter blades also make it possible to design new wind turbines that have lighter and less expensive components, such as the drive shaft, tower, and foundation. “Instead of a 24-ton rotor, you might have a 15-ton rotor. That’s substantial weight to save on the end of a long cantilevered tower,” Cripps says.

The development effort is part of American Superconductor’s strategy of bringing 10-megawatt wind turbines to market (offshore wind farms typically use 3.6-megawatt turbines or, more rarely, six-megawatt ones). It’s reducing the weight of the wind turbine generator with the help of superconductor materials, and is developing a 10-megawatt turbines that it says will weigh about as much as five-megawatt ones, to keep installation costs down.

Controlled crumpling of graphene forms artificial muscle

Jan. 23, 2013 — Duke University engineers are layering atom-thick lattices of carbon with polymers to create unique materials with a broad range of applications, including artificial muscles.

The lattice, known as graphene, is made of pure carbon and appears under magnification like chicken wire. Because of its unique optical, electrical and mechanical properties, graphene is used in electronics, energy storage, composite materials and biomedicine.

However, graphene is extremely difficult to handle in that it easily “crumples,” which, depending on circumstances, can be a positive or negative characteristic. Unfortunately, scientists have been unable to control the crumpling and unfolding of large-area graphene to take advantage of its properties.

Duke engineer Xuanhe Zhao, assistant professor in Duke’s Pratt School of Engineering, likens the challenge of controlling graphene to the difference between unfolding paper and wet tissue.

“If you crumpled up normal paper, you can pretty easily flatten it out,” Zhao said. “However, graphene is more like wet tissue paper. It is extremely thin and sticky and difficult to unfold once crumpled. We have developed a method to solve this problem and control the crumpling and unfolding of large-area graphene films.”

The Duke engineers attached the graphene on a rubber film that had been pre-stretched multiple times of its original size. Once the pre-stretch in the rubber film was relaxed, part of the graphene detached from the rubber while other part kept adhering on the rubber, forming an attached-detached pattern with a size of a few nanometers. As the rubber was relaxed, the detached graphene was compressed to crumple. Once the rubber film was stretched back, the adhered graphene will pull on the crumpled graphene to unfold it.

“In this way, the crumpling and unfolding of large-area atomic-thick graphene can be controlled by simply stretching and relaxing a rubber film, even by hand,” Zhao said.

The results were published online in the journal Nature Materials.

“Our approach has opened avenues to exploit unprecedented properties and functions of graphene,” said Jianfeng Zang, a postdoctoral fellow in Zhao’s group and the first author of the paper. “For example, we can tune the graphene from being transparent to opaque by crumpling it, and tune it back by unfolding it.”

In addition, the Duke engineers layered the graphene with different polymer films to make a “soft” material that can act like muscle tissues by contracting and expanding on demand. When electricity is applied to the graphene, the artificial muscle expands in area; when the electricity is cut off, it relaxes. Varying the voltage controls the degree of contraction and relaxation, giving actuation strains over 100 percent.

“Indeed, the crumpling and unfolding of graphene allows large deformation of the artificial muscle.” Zang said.

“New artificial muscles are enabling diverse technologies ranging from robotics and drug delivery to energy harvesting and storage,” Zhao said. “In particular, they promise to greatly improve the quality of life for millions of disabled people by providing affordable devices such as lightweight prostheses and full-page Braille displays. The broad impact of new artificial muscles is potentially analogous to the impact of piezoelectric materials on the global society.”

Zhao’s work is supported by the National Science Foundation’s (NSF) Triangle Materials Research Science and Engineering Center, NSF Materials and Surface Engineering program, and National Institutes of Health (NIH). Other members of the team are Duke’s Qiming Wang and Qing Tu.

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New Supergel Has Strange Biological Properties | Wired Science | Wired.com

Single chains of synthetic polymers (a) form bundles (b) when heated, producing a stiff gel. Paul Kouwer/Nature

Using synthetic molecules, scientists have created a gel that behaves similarly to the proteins that form a cell’s internal, shape-controlling scaffold. Eventually, the gel might be able to help heal wounds, build artificial cells, and deliver drugs to targeted areas.

Clear and colorless, the gel becomes stiffer as it’s pulled or pressed on, almost as a rubber band becomes stiffer when stretched. But unlike that rubber band, the gel’s stiffness increases disproportionately with stretching — it rapidly becomes more and more rigid. This super-stiffening behavior mimics the stress response of cytoskeletal proteins, which form a support network inside the cell that helps with locomotion and organizing internal structures.

“I can’t think of another synthetic material that shows this specific behavior,” said physicist David Weitz of Harvard University, who was not on the team that developed the gel , described today in Nature. “This is a very unusual material property, but that seems to be what nature has adapted as a way of designing her materials.”

Study coauthor Paul Kouwer , a chemist at Radboud University in the Netherlands, suggests that the gel behaves most similarly to intermediate filaments — helical, tension-bearing proteins inside cells, that are about 10 nanometers thick. He estimates a length of gel could be pulled to twice its original length.

“In every aspect that we look at – shape, dimension, mechanical properties, this is the same as the intermediate filaments,” Kouwer said.

But unlike cellular proteins, the gel is liquid at cooler temperatures. Once heated, it becomes gel-like and viscous, a transformation that is the opposite of what happens with most familiar substances, such as gelatin used in cooking — thin and runny when hot, a gelatin-containing mixture becomes thicker and more rigid when cooled. And, the gelling temperature is modifiable, meaning that scientists can make a gel that becomes optimally thick at just the right temperature — such as body temperature, for example.

Kouwer and his colleagues had been busy developing polymers for electronics and non-biological systems when they discovered a way to make an existing polymer biologically interesting. At first the team was confounded by the material they’d produced, a compound that became gel-like even when it contained 99.995 percent water.

“We sometimes said we had a supergel,” Kouwer said. “We spent two years answering why.”

The team had mixed two molecules together; these then self-assembled into a structure capable of building larger networks. One of the ingredients is a polyisocyanopeptide, which forms very stiff, long helical polymers on its own. The other is polyethylene glycol, a nontoxic compound found in everything from laxatives to solid rocket fuel. Attaching polyethylene glycol tails to the polyisocyanopeptide backbones produced a self-assembling, water-soluble helix. When heated, the twisted structure grabs its neighbors and forms stiff, networked bundles.

Tacking on different numbers of polyethylene glycol tails acts as a tuning dial, modifying the temperature at which the gel gels.

The work represents “the first semi-flexible synthetic polymers to have tunable properties,” wrote Margaret Gardel of the University of Chicago, in an opinion published in Nature. “It will be exciting to see if the authors’ approach, or other approaches for making semi-flexible polymers, can be expanded to make synthetic mimics of DNA, actin filaments and microtubules.”

In the not-too-distant future, Kouwer hopes the gel might find its way into hospitals, where it could be used for everything from wound dressings to surgical implants. Initial experiments in rodents already suggest the gel is nontoxic, he says. Warming the gel to body temperature after injecting it cold could produce a localized drug delivery vehicle. And the gel itself could be used to grow cells, or as part of a synthetic cell.

Perhaps most immediately, one could use it to fashion an easily removable bandage. Applying some of the cooler, still-liquid gel to a burn, for example, and then letting it warm to body temperature would seal the wound. To remove it? No more dreaded ripping off of wound dressings. “Just put an ice pack on,” Kouwer said. “It’ll be just as fluid as water. You can just wash it off.”