Caterpillars Inspire New Movements in Soft Robots

Some caterpillars have the extraordinary ability to rapidly curl themselves into a wheel and propel themselves away from predators. This highly dynamic process, called ballistic rolling, is one of the fastest wheeling behaviours in nature.

Researchers from Tufts University, Massachusetts, saw this as an opportunity to design a robot that mimics this behaviour of caterpillars and to develop a better understanding of the mechanics behind ballistic rolling.

The study, published on April 27, in IOP Publishing's journalBioinspiration& Biomimetics, also includes a video of both the caterpillar and robot in action and can be found athttp://www.youtube.com/watch?v=wZe9qWi-LUo.

To simulate the movement of a caterpillar, the researchers designed a 10cm long soft-bodied robot, called GoQBot, made out of silicone rubber and actuated by embedded shape memory alloy coils. It was named GoQBot as it forms a"Q" shape before rolling away at over half a meter per second.

The GoQBot was designed to specifically replicate the functional morphologies of a caterpillar, and was fitted with 5 infrared emitters along its side to allow motion tracking using one of the latest high speed 3D tracking systems. Simultaneously, a force plate measured the detailed ground forces as the robot pushed off into a ballistic roll.

In order to change its body conformation so quickly, in less than 100 ms, GoQBot benefits from a significant degree of mechanical coordination in ballistic rolling. Researchers believe such coordination is mediated by the nonlinear muscle coupling in the animals.

The researchers were also able to explain why caterpillars don't use the ballistic roll more often as a default mode of transport; despite its impressive performance, ballistic rolling is only effective on smooth surfaces, demands a large amount of power, and often ends unpredictably.

Not only did the study provide an insight into the fascinating escape system of a caterpillar, it also put forward a new locomotor strategy which could be used in future robot development.

Many modern robots are modelled after snakes, worms and caterpillars for their talents in crawling and climbing into difficult spaces. However, the limbless bodies severely reduce the speeds of the robots in the opening. On the other hand, there are many robots that employ a rolling motion in order to travel with speed and efficiency, but they struggle to gain access to difficult spaces.

Lead author Huai-Ti Lin from the Department of Biology, Tufts University, said:"GoQBot demonstrates a solution by reconfiguring its body and could therefore enhance several robotic applications such as urban rescue, building inspection, and environmental monitoring."

"Due to the increased speed and range, limbless crawling robots with ballistic rolling capability could be deployed more generally at a disaster site such as a tsunami aftermath. The robot can wheel to a debris field and wiggle into the danger for us."

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NASA Technology Looks Inside Japan's Nuclear Reactor

The iRobot PackBot employs technologies used previously in the design of"Rocky-7," which served as a terrestrial test bed at JPL for the current twin Mars rovers, Spirit and Opportunity. PackBot's structural features are modeled after Rocky-7, including the lightweight, high-torque actuators that control the rover; and its strong, lightweight frame structure and sheet-metal chassis.

PackBot's other"ancestor," called Urbie, was an urban reconnaissance robot with military and disaster response applications. Urbie's lightweight structure and rugged features also made it useful in emergency response situations; for example, at sites contaminated with radiation and chemical spills, and at buildings damaged by earthquakes. Urbie's physical structure was designed by iRobot Corp., Bedford, Mass., while JPL was responsible for the intelligent robot's onboard sensors and vision algorithms, which helped the robot factor in obstacles and determine an appropriate driving path. Following the success of Urbie's milestones, the team at iRobot created its successor: PackBot.

Since 2002, iRobot has delivered variations of the PackBot model to the U.S. Army, U.S. Air Force and U.S. Navy. The tactical robot's first military deployment was to Afghanistan in July 2002, to assist soldiers by providing"eyes and ears" in the most dangerous or inaccessible areas. It was also used to search through debris at Ground Zero after the Sept. 11, 2001 attacks in New York.

Recently, iRobot provided two PackBots to help after the devastating March 11, 2011, earthquake and tsunami in Japan. The PackBot models, currently taking radioactivity readings in the damaged Fukushima Daiichi nuclear power plant buildings, are equipped with multiple cameras and hazard material sensors. The images and readings provided by the PackBots indicated radiation levels are still too high to allow human repair crews to safely enter the buildings.

Urbie was a joint effort of the Defense Advanced Research Project's Agency's (DARPA) Tactical Mobile Robot program, JPL, iRobot Corp., the Robotics Institute of Carnegie Mellon University, and the University of Southern California's Robotics Research Laboratory. JPL is managed for NASA by the California Institute of Technology in Pasadena.

For more information on the history of the partnership between iRobot and JPL, visit:http://www.sti.nasa.gov/tto/Spinoff2005/ps_1.html.

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Origami Not Just for Paper Anymore: DNA, Folded Into Complex Shapes, Could Have a Big Impact on Nanotechnology

Trying to build DNA structures on a large scale was once considered unthinkable. But about five years ago, Caltech computational bioengineer Paul Rothemund laid out a new design strategy called DNA origami: the construction of two-dimensional shapes from a DNA strand folded over on itself and secured by short"staple" strands. Several years later, William Shih's lab at Harvard Medical School translated this concept to three dimensions, allowing design of complex curved and bent structures that opened new avenues for synthetic biological design at the nanoscale.

A major hurdle to these increasingly complex designs has been automation of the design process. Now a team at MIT, led by biological engineer Mark Bathe, has developed software that makes it easier to predict the three-dimensional shape that will result from a given DNA template. While the software doesn't fully automate the design process, it makes it considerably easier for designers to create complex 3-D structures, controlling their flexibility and potentially their folding stability.

"We ultimately seek a design tool where you can start with a picture of the complex three-dimensional shape of interest, and the algorithm searches for optimal sequence combinations," says Bathe, the Samuel A. Goldblith Assistant Professor of Applied Biology."In order to make this technology for nanoassembly available to the broader community -- including biologists, chemists, and materials scientists without expertise in the DNA origami technique -- the computational tool needs to be fully automated, with a minimum of human input or intervention."

Bathe and his colleagues described their new software in the Feb. 25 issue ofNature Methods. In that paper, they also provide a primer on creating DNA origami with collaborator Hendrik Dietz at the Technische Universitaet Muenchen."One bottleneck for making the technology more broadly useful is that only a small group of specialized researchers are trained in scaffolded DNA origami design," Bathe says.

Programming DNA

DNA consists of a string of four nucleotide bases known as A, T, G and C, which make the molecule easy to program. According to nature's rules, A binds only with T, and G only with C."With DNA, at the small scale, you can program these sequences to self-assemble and fold into a very specific final structure, with separate strands brought together to make larger-scale objects," Bathe says.

Rothemund's origami design strategy is based on the idea of getting a long strand of DNA to fold in two dimensions, as if laid on a flat surface. In his first paper outlining the method, he used a viral genome consisting of approximately 8,000 nucleotides to create 2-D stars, triangles and smiley faces.

That single strand of DNA serves as a"scaffold" for the rest of the structure. Hundreds of shorter strands, each about 20 to 40 bases in length, combine with the scaffold to hold it in its final, folded shape.

"DNA is in many ways better suited to self-assembly than proteins, whose physical properties are both difficult to control and sensitive to their environment," Bathe says.

Bathe's new software program interfaces with a software program from Shih's lab called caDNAno, which allows users to manually create scaffolded DNA origami from a two-dimensional layout. The new program, dubbed CanDo, takes caDNAno's 2-D blueprint and predicts the ultimate 3-D shape of the design. This resulting shape is often unintuitive, Bathe says, because DNA is a flexible object that twists, bends and stretches as it folds to form a complex 3-D shape.

According to Rothemund, the CanDo program should allow DNA origami designers to more thoroughly test their DNA structures and tweak them to fold correctly."While we have been able to design the shape of things, we have had no tools to easily design and analyze the stresses and strains in those shapes or to design them for specific purposes," he says.

At the molecular-level, stress in the double helix of DNA decreases the folding stability of the structure and introduces local defects, both of which have hampered progress in the scaffolded DNA origami field.

Postdoctoral researcher Do-Nyun Kim and graduate student Matthew Adendorff, both of the Bathe lab, are now furthering CanDo's capabilities and optimizing the scaffolded DNA origami design process.

Building nanoscale tools

Once scientists have a reliable way to assemble DNA structures, the next question is what to do with them. One application scientists are excited about is a"DNA carrier" that can transport drugs to specific destinations in the body such as tumors, where the carrier would release the cargo based on a specific chemical signal from the target cancer cell.

Another possible application of scaffolded DNA origami could help reproduce part of the light-harvesting apparatus of photosynthetic plant cells. Researchers hope to recreate that complex series of about 20 protein subunits, but to do that, components must be held together in specific positions and orientations. That's where DNA origami could come in.

"DNA origami enables the nanoscale construction of very precise architectural arrangements. Researchers are exploiting this unique property to pursue a number of applications at the nanoscale, including a synthetic photocell," Bathe says."While applications such as this are still quite far off on the horizon, we believe that predictive engineering software tools are essential for progress in this direction."

Novel applications may also grow out of a new competition being held at Harvard this summer, called BIOMOD. Undergraduate teams from about a dozen schools, including MIT, Harvard and Caltech, will try to design nanoscale biomolecules for robotics, computing and other applications.

In the meantime, Bathe is focusing on further developing CanDo to enable automated DNA origami design."Once you have an automated computational tool that allows you to design complex shapes in a precise way, I think we're in a much better position to exploit this technology for interesting applications," he says.

For DNA origami to have a broad impact, it needs to become routine to simply order up DNA parts to build any configuration you can dream up, Bathe says. He notes:"Once non-specialists can design arbitrary 3-D nanostructures using DNA origami, their imaginations can run free."

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Neurorobotics Reveals Brain Mechanisms of Self-Consciousness

Recent theories of self-consciousness highlight the importance of integrating many different sensory and motor signals, but it is not clear how this type of integration induces subjective states such as self-location ("Where am I in space?") and the first-person perspective ("From where do I perceive the world?"). Studies of neurological patients reporting out-of-body experiences have provided some evidence that brain damage interfering with the integration of multisensory body information may lead to pathological changes of the first-person perspective and self-location. However, it is still not known how to examine brain mechanisms associated with self-consciousness.

"Recent behavioral and physiological work, using video-projection and various visuo-tactile conflicts showed that self-location can be manipulated in healthy participants," explains senior study author, Dr. Olaf Blanke, from the Ecole Polytechnique Fédérale de Lausanne in Switzerland."However, so far these experimental findings and techniques do not allow for the induction of changes in the first-person perspective and have not been integrated with neuroimaging, probably because the experimental set-ups require participants to sit, stand, or move. This makes it very difficult to apply and film the visuo-tactile conflicts on the participant's body during standard brain imaging techniques."

Making use of inventive neuroimaging-compatible robotic technology that was developed by Dr. Gassert's group at the Swiss Federal Institute of Technology in Zurich, Dr. Blanke and colleagues studied healthy subjects and employed specific bodily conflicts that induced changes in self-location and first-person perspective while simultaneously monitoring brain activity with functional magnetic resonance imaging. They observed that TPJ activity reflected experimental changes in self-location and first-person perspective. The researchers also completed a large study of neurological patients with out-of-body experiences and found that brain damage was localized to the TPJ.

"Our results illustrate the power of merging technologies from engineering with those of neuroimaging and cognitive science for the understanding of the nature of one of the greatest mysteries of the human mind: self-consciousness and its neural mechanisms," concludes Dr. Blanke."Our findings on experimentally and pathologically induced altered states of self-consciousness present a powerful new research technology and reveal that TPJ activity reflects one of the most fundamental subjective feelings of humans: the feeling that 'I' am an entity that is localized at a position in space and that 'I' perceive the world from here."

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Fat Turns Into Soap in Sewers, Contributes to Overflows

"We found that FOG deposits in sewage collection systems are created by chemical reactions that turn the fatty acids from FOG into, basically, a huge lump of soap," says Dr. Joel Ducoste, a professor of civil, construction and environmental engineering at NC State and co-author of a paper describing the research. Collection systems are the pipes and pumping stations that carry wastewater from homes and businesses to sewage-treatment facilities.

These hardened FOG deposits reduce the flow of wastewater in the pipes, contributing to sewer overflows -- which can cause environmental and public-health problems and lead to costly fines and repairs.

The research team used a technique called Fourier Transform Infrared (FTIR) spectroscopy to determine what the FOG deposits were made of at the molecular level. FTIR spectroscopy shoots a sample material with infrared light at various wavelengths. Different molecular bonds vibrate in response to different wavelengths. By measuring which infrared wavelengths created vibrations in their FOG samples, researchers were able to determine each sample's molecular composition.

Using this technique, researchers confirmed that the hardened deposits were made of calcium-based fatty acid salts -- or soap.

"FOG itself cannot create these deposits," Ducoste says."The FOG must first be broken down into its constituent parts: glycerol and free fatty acids. These free fatty acids -- specifically, saturated fatty acids -- can react with calcium in the sewage collection system to form the hardened deposits.

"Until this point we did not know how these deposits were forming -- it was just a hypothesis," Ducoste says."Now we know what's going on with these really hard deposits."

The researchers are now focused on determining where the calcium in the collection system is coming from, and how quickly these deposits actually form. Once they've resolved those questions, Ducoste says, they will be able to create numerical models to predict where a sewage system may have"hot spots" that are particularly susceptible to these blockages.

Ultimately, Ducoste says,"if we know how -- and how quickly -- these deposits form, it may provide scientific data to support policy decisions related to preventing sewer overflows."

The research was funded by the Water Resources Research Institute and the U.S. Environmental Protection Agency.

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Development in Fog Harvesting Process May Make Water Available to the World’s Poor

What nature has developed, Shreerang Chhatre wants to refine, to help the world's poor. Chhatre is an engineer and aspiring entrepreneur at MIT who works on fog harvesting, the deployment of devices that, like the beetle, attract water droplets and corral the runoff. This way, poor villagers could collect clean water near their homes, instead of spending hours carrying water from distant wells or streams. In pursuing the technical and financial sides of his project, Chhatre is simultaneously a doctoral candidate in chemical engineering at MIT; an MBA student at the MIT Sloan School of Management; and a fellow at MIT's Legatum Center for Development and Entrepreneurship.

Access to water is a pressing global issue: the World Health Organization and UNICEF estimate that nearly 900 million people worldwide live without safe drinking water. The burden of finding and transporting that water falls heavily on women and children."As a middle-class person, I think it's terrible that the poor have to spend hours a day walking just to obtain a basic necessity," Chhatre says.

A fog-harvesting device consists of a fence-like mesh panel, which attracts droplets, connected to receptacles into which water drips. Chhatre has co-authored published papers on the materials used in these devices, and believes he has improved their efficacy."The technical component of my research is done," Chhatre says. He is pursuing his work at MIT Sloan and the Legatum Center in order to develop a workable business plan for implementing fog-harvesting devices.

Interest in fog harvesting dates to the 1990s, and increased when new research on Stenocara gracilipes made a splash in 2001. A few technologists saw potential in the concept for people. One Canadian charitable organization, FogQuest, has tested projects in Chile and Guatemala.

Chhatre's training as a chemical engineer has focused on the wettability of materials, their tendency to either absorb or repel liquids (think of a duck's feathers, which repel water). A number of MIT faculty have made advances in this area, including Robert Cohen of the Department of Chemical Engineering; Gareth McKinley of the Department of Mechanical Engineering; and Michael Rubner of the Department of Materials Science and Engineering. Chhatre, who also received his master's degree in chemical engineering from MIT in 2009, is co-author, with Cohen and McKinley among other researchers, of three published papers on the kinds of fabrics and coatings that affect wettability.

One basic principle of a good fog-harvesting device is that it must have a combination of surfaces that attract and repel water. For instance, the shell of Stenocara gracilipes has bumps that attract water and troughs that repel it; this way, drops collects on the bumps, then run off through the troughs without being absorbed, so that the water reaches the beetle's mouth.

To build fog-harvesting devices that work on a human scale, Chhatre says,"The idea is to use the design principles we developed and extend them to this problem."

To build larger fog harvesters, researchers generally use mesh, rather than a solid surface like a beetle's shell, because a completely impermeable object creates wind currents that will drag water droplets away from it. In this sense, the beetle's physiology is an inspiration for human fog harvesting, not a template."We tried to replicate what the beetle has, but found this kind of open permeable surface is better," Chhatre says."The beetle only needs to drink a few micro-liters of water. We want to capture as large a quantity as possible."

In some field tests, fog harvesters have captured one liter of water (roughly a quart) per one square meter of mesh, per day. Chhatre and his colleagues are conducting laboratory tests to improve the water collection ability of existing meshes.

FogQuest workers say there is more to fog harvesting than technology, however."You have to get the local community to participate from the beginning," says Melissa Rosato, who served as project manager for a FogQuest program that has installed 36 mesh nets in the mountaintop village of Tojquia, Guatemala, and supplies water for 150 people."They're the ones who are going to be managing and maintaining the equipment." Because women usually collect water for households, Rosato adds,"If women are not involved, chances of a long-term sustainable project are slim."

Whatever Chhatre's success in the laboratory, he agrees it will not be easy to turn fog-harvesting technology into a viable enterprise."My consumer has little monetary power," he notes. As part of his Legatum fellowship and Sloan studies, Chhatre is analyzing which groups might use his potential product. Chhatre believes the technology could also work on the rural west coast of India, north of Mumbai, where he grew up.

Another possibility is that environmentally aware communities, schools or businesses in developed countries might try fog harvesting to reduce the amount of energy needed to obtain water."As the number of people and businesses in the world increases and rainfall stays the same, more people will be looking for alternatives," says Robert Schemenauer, the executive director of FogQuest.

Indeed, the importance of water-supply issues globally is one reason Chhatre was selected for his Legatum fellowship.

"We welcomed Shreerang as a Legatum fellow because it is an important problem to solve," notes Iqbal Z. Quadir, director of the Legatum Center."About one-third of the planet's water that is not saline happens to be in the air. Collecting water from thin air solves several problems, including transportation. If people do not spend time fetching water, they can be productively employed in other things which gives rise to an ability to pay. Thus, if this technology is sufficiently advanced and a meaningful amount of water can be captured, it could be commercially viable some day."

Quadir also feels that if Chhatre manages to sell a sufficient number of collection devices in the developed world, it could contribute to a reduction in price, making it more viable in poor countries."The aviation industry in its infancy struggled with balloons, but eventually became a viable global industry," Quadir adds."Shreerang's project addresses multiple problems at the same time and, after all, the water that fills our rivers and lakes comes from air."

That said, fog harvesting remains in its infancy, technologically and commercially, as Chhatre readily recognizes."This is still a very open problem," he says."It's a work in progress."

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Starting a New Metabolic Path: New Technique Will Help Metabolic Engineering

"Metabolic engineers and synthetic biologists can use our directed proteomic technique to get useful information about protein levels in their organisms, which in turn can be used to direct valuable followup experiments," says Christopher Petzold, chemist and deputy director for proteomics at JBEI, who led this research."We believe that targeted proteomics is a useful tool that fills a much needed gap in efforts to engineer new metabolic pathways for microbes."

Petzold, who also holds an appointment with the Lawrence Berkeley National Laboratory (Berkeley Lab)'s Physical Biosciences Division, is the corresponding author on a paper describing this research that was published in the journalMetabolic Engineering.

Metabolic engineering is the practice of altering genes and chemical pathways within a cell or microorganism to increase production of a specific chemical substance. It is fast becoming one of the principal techniques of modern biotechnology for the microbial production of chemicals that are currently derived from non-renewable resources or from natural resources that are limited. Critical to the success of metabolic engineering efforts are techniques that enable researchers to assemble and optimize novel metabolic pathways in microbes. Given that such pathways often involve multiple different factors, performance- hampering problems, such as the abundance of proteins and messenger RNA, or the activity of enzymes, are not always evident simply by measuring the amount of final product obtained.

"Synthetic biologists and metabolic engineers will utilize a variety of analytical methods to identify the parts of a metabolic pathway that limit production," Petzold says."At the metabolite level, for example, monitoring all pathway intermediates helps identify bottlenecks where further engineering could improve the final product titer. However, pathways that divert intermediates to native processes at the cost of final product formation may disguise the actual location of a bottleneck."

Researchers have tried developing assays to evaluate every intermediate in a given metabolic pathway but this has been a major challenge because intermediates often degrade rapidly or are isomers, and because there are few available standards for such evaluations.

"Engineers are often left to guess at the metabolite levels in parts of the pathway," Petzold says.

Targeted proteomics is based on a variation of mass spectrometry called selected-reaction monitoring (SRM) that can be used to rapidly detect and quantify multiple target proteins within complex protein mixtures, such as those found in cells or microbes. When coupled to liquid chro­matography (LC),SRM mass spectrometry analysis provides high selectivity and sensitivity through the elimination of background signal and noise even in the most complex mix of proteins. This is made possible by selecting only two points of mass for monitoring -- a peptide mass and a specific fragment mass -- rather than scanning the entire mass range.

"Carrying out targeted proteomics through SRM mass spectrometry analysis is most useful when quantification of multiple proteins in a single sample is desired," Petzold says."Working with protein-specific peptides, you can analyze 20 or more targeted proteins in an hour, and entire engineered metabolic pathways can be quantified in a single experiment, something that isn't practical with conventional immunoblot analysis."

Petzold and his co-authors demonstrated the effectiveness of their targeted proteomics technique when they used it to measure protein levels inEscherichia colithat were engineered with yeast proteins to produce amorpha-4,11-diene, a member of the family of plant chemicals known as sesquiterpenes. Strains ofE. colicontaining a high flux mevalonate pathway have the potential to provide a vast range of high value sesquiterpenes and other isoprenoid-based chemical compounds, which today are typically obtained from petrochemical or plant sources.

Our analysis identified two mevalonate pathway proteins, mevalonate kinase and phosphomevalonate kinase, both from yeast, as potential bottlenecks," Petzold says."Codon-optimization of the genes encoding mevalonate kinase and phosphomevalonate kinase, and expression from a stronger promoter led to significantly improved levels of these two proteins and a more than three-fold improvement in the final amorpha-4,11-diene titer, greater than 500 milligrams per liter."

Petzold and his JBEI colleagues are now in the process of implementing"scheduled-SRM," a variation of the SRM mass spectrometry analysis that would allow them to easily detect and quantify 100 proteins in a single experiment that can be completed in less than two hours.

This research was supported by JBEI through the DOE Office of Science. JBEI is one of three Bioenergy Research Centers funded by the U.S. Department of Energy to advance the development of the next generation of biofuels.

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Scientists Engineer Nanoscale Vaults to Encapsulate 'Nanodisks' for Drug Delivery

The development of new methods that use engineered nanomaterials to transport drugs and release them directly into cells holds great potential in this area. And while several such drug-delivery systems -- including some that use dendrimers, liposomes or polyethylene glycol -- have won approval for clinical use, they have been hampered by size limitations and ineffectiveness in accurately targeting tissues.

Now, researchers at UCLA have developed a new and potentially far more effective means of targeted drug delivery using nanotechnology.

In a study to be published in the May 23 print issue of the journalSmall, they demonstrate the ability to package drug-loaded"nanodisks" into vault nanoparticles, naturally occurring nanoscale capsules that have been engineered for therapeutic drug delivery. The study represents the first example of using vaults toward this goal.

The UCLA research team was led by Leonard H. Rome and included his colleagues Daniel C. Buehler and Valerie Kickhoefer from the UCLA Department of Biological Chemistry; Daniel B. Toso and Z. Hong Zhou from the UCLA Department of Microbiology, Immunology and Molecular Genetics; and the California NanoSystems Institute (CNSI) at UCLA.

Vault nanoparticles are found in the cytoplasm of all mammalian cells and are one of the largest known ribonucleoprotein complexes in the sub-100-nanometer range. A vault is essentially barrel-shaped nanocapsule with a large, hollow interior -- properties that make them ripe for engineering into a drug-delivery vehicles. The ability to encapsulate small-molecule therapeutic compounds into vaults is critical to their development for drug delivery.

Recombinant vaults are nonimmunogenic and have undergone significant engineering, including cell-surface receptor targeting and the encapsulation of a wide variety of proteins.

"A vault is a naturally occurring protein particle and so it causes no harm to the body," said Rome, CNSI associate director and a professor of biological chemistry."These vaults release therapeutics slowly, like a strainer, through tiny, tiny holes, which provides great flexibility for drug delivery."

The internal cavity of the recombinant vault nanoparticle is large enough to hold hundreds of drugs, and because vaults are the size of small microbes, a vault particle containing drugs can easily be taken up into targeted cells.

With the goal of creating a vault capable of encapsulating therapeutic compounds for drug delivery, UCLA doctoral student Daniel Buhler designed a strategy to package another nanoparticle, known as a nanodisk (ND), into the vault's inner cavity, or lumen.

"By packaging drug-loaded NDs into the vault lumen, the ND and its contents would be shielded from the external medium," Buehler said."Moreover, given the large vault interior, it is conceivable that multiple NDs could be packaged, which would considerably increase the localized drug concentration."

According to researcher Zhou, a professor of microbiology, immunology and molecular genetics and director of the CNSI's Electron Imaging Center for NanoMachines, electron microscopy and X-ray crystallography studies have revealed that both endogenous and recombinant vaults have a thin protein shell enclosing a large internal volume of about 100,000 cubic nanometers, which could potentially hold hundreds to thousands of small-molecular-weight compounds.

"These features make recombinant vaults an attractive target for engineering as a platform for drug delivery," Zhou said."Our study represents the first example of using vaults toward this goal."

"Vaults can have a broad nanosystems application as malleable nanocapsules," Rome added.

The recombinant vaults are engineered to encapsulate the highly insoluble and toxic hydrophobic compound all-trans retinoic acid (ATRA) using a vault-binding lipoprotein complex that forms a lipid bilayer nanodisk.

The research was supported by the UC Discovery Grant Program, in collaboration with the research team's corporate sponsor, Abraxis Biosciences Inc., and by the Mather's Charitable Foundation and an NIH/NIBIB Award.

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Functioning Synapse Created Using Carbon Nanotubes: Devices Might Be Used in Brain Prostheses or Synthetic Brains

The team, which was led by Professor Alice Parker and Professor Chongwu Zhou in the USC Viterbi School of Engineering Ming Hsieh Department of Electrical Engineering, used an interdisciplinary approach combining circuit design with nanotechnology to address the complex problem of capturing brain function.

In a paper published in the proceedings of the IEEE/NIH 2011 Life Science Systems and Applications Workshop in April 2011, the Viterbi team detailed how they were able to use carbon nanotubes to create a synapse.

Carbon nanotubes are molecular carbon structures that are extremely small, with a diameter a million times smaller than a pencil point. These nanotubes can be used in electronic circuits, acting as metallic conductors or semiconductors.

"This is a necessary first step in the process," said Parker, who began the looking at the possibility of developing a synthetic brain in 2006."We wanted to answer the question: Can you build a circuit that would act like a neuron? The next step is even more complex. How can we build structures out of these circuits that mimic the function of the brain, which has 100 billion neurons and 10,000 synapses per neuron?"

Parker emphasized that the actual development of a synthetic brain, or even a functional brain area is decades away, and she said the next hurdle for the research centers on reproducing brain plasticity in the circuits.

The human brain continually produces new neurons, makes new connections and adapts throughout life, and creating this process through analog circuits will be a monumental task, according to Parker.

She believes the ongoing research of understanding the process of human intelligence could have long-term implications for everything from developing prosthetic nanotechnology that would heal traumatic brain injuries to developing intelligent, safe cars that would protect drivers in bold new ways.

For Jonathan Joshi, a USC Viterbi Ph.D. student who is a co-author of the paper, the interdisciplinary approach to the problem was key to the initial progress. Joshi said that working with Zhou and his group of nanotechnology researchers provided the ideal dynamic of circuit technology and nanotechnology.

"The interdisciplinary approach is the only approach that will lead to a solution. We need more than one type of engineer working on this solution," said Joshi."We should constantly be in search of new technologies to solve this problem."

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RNA Nanoparticles Constructed to Safely Deliver Long-Lasting Therapy to Cells

In two new publications in the journal Molecular Therapy, University of Cincinnati (UC) biomedical engineering professor Peixuan Guo, PhD, details successful methods of producing large RNA nanoparticles and testing their safety in the delivery of therapeutics to targeted cells.

The articles, in advance online publication, represent"two very important milestones in RNA nanotherapy," says Guo.

"One problem in RNA therapy is the requirement for the generation of relatively large quantities of RNA," he says."In this research, we focused on solving the most challenging problem of industry-scale production of large RNA molecules by a bipartite approach, finding that pRNA can be assembled from two pieces of smaller RNA modules."

Guo, Dane and Mary Louise Miller Endowed Chair of biomedical engineering, serves as director of the National Cancer Institute (NCI) Alliance for Nanotechnology in Cancer Platform Partnership Program at UC. He has focused his research on RNA for decades, pioneering its use as a versatile building block for nanotechnology, or for the engineering of functional systems at the molecular scale. In 1987, he discovered a packaging RNA (pRNA) in the bacteriophage phi29 virus which can gear a motor to package DNA into the viral protein shell. In 1998, his lab discovered that pRNA can self-assemble or be engineered into nanoparticles to gear the motor.

In his most recent research, Guo and colleagues detail multiple approaches for the construction of a functional 117-base pRNA molecule containing small interfering RNA (siRNA). siRNA has already been shown to be an efficient tool for silencing genes in cells, but previous attempts have produced chemically modified siRNA lasting only 15-45 minutes in the body and often inducing undesired immune responses.

"The pRNA particles we constructed to harbor siRNA have a half life of between five and 10 hours in animal models, are non-toxic and produce no immune response," says Guo."The tenfold increase of circulation time in the body is important in drug development and paves the way towards clinical trials of RNA nanoparticles as therapeutic drugs."

Guo says the size of the constructed pRNA molecule is crucial for the effective delivery of therapeutics to diseased tissues.

"RNA nanoparticles must be within the range of 15 to 50 nanometers," he says,"large enough to be retained by the body and not enter cells randomly, causing toxicity, but small enough to enter the targeted cells with the aid of cell surface receptions.

In the paper,"Assembly of Therapeutic pRNA-siRNA Nanoparticles Using Bipartite Approach," Guo and his colleagues used two synthetic RNA fragments to create the 117-base pRNA, which was able to further assemble with other pRNA molecules and function in the bacteriophage phi29 viral motor to package DNA.

"The two-piece approach in pRNA synthesis overcame challenges of size limitations in chemical synthesis of RNA nanoparticles," Guo wrote."The resulting nanoparticles were competent in delivering and releasing therapeutics to cells and silencing the genes within them. The ability to chemically synthesize these nanoparticles allows for further chemical modification of RNA for stability and specific targeting."

The second publication,"Pharmacological Characterization of Chemically Synthesized Monomeric phi29 pRNA Nanoparticles for Systemic Delivery," builds on that research, demonstrating that modified three-dimensional pRNA nanoparticles were readily manufactured through the two-piece approach. The modified nanoparticles were resistant to common enzymes that can attack and degrade RNA and remained chemically and metabolically stable.

Furthermore, when delivered to target cells in an animal model, the nanoparticles were non-toxic and did not induce an immune response, enabling the nanoparticles to bind to cancer cells in vivo.

Previous studies have encased therapeutic siRNA in a polymer coating or liposome for delivery to cells.

"To our knowledge, this is the first naked RNA nanoparticles to have been comprehensively examined pharmacologically in vivo and demonstrated to be safe, as well as deliver itself to tumor tissues by a specific targeting mechanism," he says."It suggests that the pRNA nanoparticles without coating have all the preferred pharmacological features to serve as an efficient nanodelivery platform for broad medical applications."

Co-authors of"Assembly of Therapeutic pRNA-siRNA Nanoparticles Using Bipartite Approach" include Yi Shu, Mathieu Cinier, Sejal Fox and Nira Ben-Johnathan of the University of Cincinnati.

Co-authors of"Pharmacological Characterization of Chemically Synthesized Monomeric phi29 pRNA Nanoparticles for Systemic Delivery" include Sherine Abdelmawla and Songchuan Guo of Kylin Therapeutics and Purdue University, Limin Zhang, Sai M Pulukuri, Prithviraj Patankar, Patrick Conley, Joseph Trebley and Qi-Xiang Li of Kylin Therapeutics.

This study was funded by National Cancer Institute, National Institute of Biomedical Imaging and Bioengineering, National Institute of General Medical Sciences and Kylin Therapeutics Inc. Guo is co-founder of Kylin Therapuetics.

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New Biosensor Microchip Could Speed Up Drug Development, Researchers Say

A single centimeter-sized array of the nanosensors can simultaneously and continuously monitor thousands of times more protein-binding events than any existing sensor. The new sensor is also able to detect interactions with greater sensitivity and deliver the results significantly faster than the present"gold standard" method.

"You can fit thousands, even tens of thousands, of different proteins of interest on the same chip and run the protein-binding experiments in one shot," said Shan Wang, a professor of materials science and engineering, and of electrical engineering, who led the research effort.

"In theory, in one test, you could look at a drug's affinity for every protein in the human body," said Richard Gaster, MD/PhD candidate in bioengineering and medicine, who is the first author of a paper describing the research that is in the current issue ofNature Nanotechnology,available online now.

The power of the nanosensor array lies in two advances. First, the use of magnetic nanotags attached to the protein being studied -- such as a medication -- greatly increases the sensitivity of the monitoring.

Second, an analytical model the researchers developed enables them to accurately predict the final outcome of an interaction based on only a few minutes of monitoring data. Current techniques typically monitor no more than four simultaneous interactions and the process can take hours.

"I think their technology has the potential to revolutionize how we do bioassays," said P.J. Utz, associate professor of medicine (immunology and rheumatology) at Stanford University Medical Center, who was not involved in the research.

A microchip with a nanosensor array (orange squares) is shown with a different protein (various colors) attached to each sensor. Four proteins of a potential medication (blue Y-shapes), with magnetic nanotags attached (grey spheres), have been added. One medication protein is shown binding with a protein on a nanosensor.

Members of Wang's research group developed the magnetic nanosensor technology several years ago and demonstrated its sensitivity in experiments in which they showed that it could detect a cancer-associated protein biomarker in mouse blood at a thousandth of the concentration that commercially available techniques could detect. That research was described in a 2009 paper inNature Medicine.

The researchers tailor the nanotags to attach to the particular protein being studied. When a nanotag-equipped protein binds with another protein that is attached to a nanosensor, the magnetic nanotag alters the ambient magnetic field around the nanosensor in a small but distinct way that is sensed by the detector.

"Let's say we are looking at a breast cancer drug," Gaster said."The goal of the drug is to bind to the target protein on the breast cancer cells as strongly as possible. But we also want to know: How strongly does that drug aberrantly bind to other proteins in the body?"

To determine that, the researchers would put breast cancer proteins on the nanosensor array, along with proteins from the liver, lungs, kidneys and any other kind of tissue that they are concerned about. Then they would add the medication with its magnetic nanotags attached and see which proteins the drug binds with -- and how strongly.

"We can see how strongly the drug binds to breast cancer cells and then also how strongly it binds to any other cells in the human body such as your liver, kidneys and brain," Gaster said."So we can start to predict the adverse affects to this drug without ever putting it in a human patient."

It is the increased sensitivity to detection that comes with the magnetic nanotags that enables Gaster and Wang to determine not only when a bond forms, but also its strength.

"The rate at which a protein binds and releases, tells how strong the bond is," Gaster said. That can be an important factor with numerous medications.

"I am surprised at the sensitivity they achieved," Utz said."They are detecting on the order of between 10 and 1,000 molecules and that to me is quite surprising."

The nanosensor is based on the same type of sensor used in computer hard drives, Wang said.

"Because our chip is completely based on existing microelectronics technology and procedures, the number of sensors per area is highly scalable with very little cost," he said.

Although the chips used in the work described in theNature Nanotechnologypaper had a little more than 1,000 sensors per square centimeter, Wang said it should be no problem to put tens of thousands of sensors on the same footprint.

"It can be scaled to over 100,000 sensors per centimeter, without even pushing the technology limits in microelectronics industry," he said.

Wang said he sees a bright future for increasingly powerful nanosensor arrays, as the technology infrastructure for making such nanosensor arrays is in place today.

"The next step is to marry this technology to a specific drug that is under development," Wang said."That will be the really killer application of this technology."

Other Stanford researchers who participated in the research and are coauthors of theNature Nanotechnologypaper are Liang Xu and Shu-Jen Han, both of whom were graduate students in materials science and engineering at the time the research was done; Robert Wilson, senior scientist in materials science and engineering; and Drew Hall, graduate student in electrical engineering. Other coauthors are Drs. Sebastian Osterfeld and Heng Yu from MagArray Inc. in Sunnyvale. Osterfeld and Yu are former alumni of the Wang Group.

Funding for the research came from the National Cancer Institute, the National Science Foundation, the Defense Advanced Research Projects Agency, the Gates Foundation and National Semiconductor Corporation.

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Miniature Invisibility 'Carpet Cloak' Hides More Than Its Small Size Implies

This places serious constraints on practical applications, particularly for the optoelectronics industry, where size is a premium and any cloaking device would need to be both tiny and delicate.

An international team of physicists from the Technical University of Denmark (DTU), the University of Birmingham, UK, and Imperial College London, however, may have overcome this size limitation by using a technology known as a"carpet cloaks," which can conceal a much larger area than other cloaking techniques of comparable size. The researchers achieved their result by using metamaterials, artificial materials engineered to have optical properties not found in nature. They describe their approach in the Optical Society's (OSA) open-access journalOptics Express.

Jingjing Zhang, a postdoctoral researcher at DTU's Fotonik Department of Photonics Engineering and Structured Electromagnetic Materials, and an author of the Optics Express paper, explains that the team's new carpet cloak, which is based on an alternating-layer structure on a silicon-on-insulator (SOI) platform, introduces a flexible way to address the size problem.

"This new cloak, consisting of metamaterials, was designed with a grating structure that is simpler than previous metamaterial structures for cloaks," she says.

Grating structures channel light of a particular wavelength around an object. A grating structure is simply a series of slits or openings that redirect a beam of light.

"The highly anisotropic material comprising the cloak is obtained by adopting semiconductor manufacturing techniques that involve patterning the top silicon layer of an SOI wafer with nanogratings of appropriate filling factor. This leads to a cloak only a few times larger than the cloaked object," says Zhang. In this case, filling factor simply refers to the size of the grating structure and determines the wavelengths of light that are affected by the cloak.

By precisely restoring the path of the reflecting wave from the surface, the cloak creates an illusion of a flat plane for a triangular bump on the surface -- hiding its presence over wavelengths ranging from 1480nm to 1580nm.

In less technical terms, the carpet cloaks work by essentially disguising an object from light, making it appear like a flat ground plane.

"The cloak parameters can be tweaked by tuning the filling factor and the orientation of the layers," says Zhang."Therefore, layered materials bypass the limitation of natural materials at hand and give us extra freedom to design the devices as desired." In contrast to previous works based on nanostructures, the cloaking carpet used in this work also shows advantages of easier design and fabrication.

The cloak is made exclusively of dielectric materials that are highly transparent to infrared light, so the cloak itself is very efficient and absorbs a negligible fraction of energy.

Zhang and her colleagues are also looking at ways of improving the technology. They report in their Optics Express paper that even though the cloaking ensures that the beam shape is unaffected by the presence of the object, the beam intensity is slightly reduced. They attribute this to reflection at the cloak's surface, and partly by imperfections of the fabrication. They also determined that adding an additional layer of material around the cloak and improving uniformity of the grating would help eliminate reflection and scattering issues.

"Although our experiment was carried out at near-infrared frequencies, this design strategy is applicable in other frequency ranges," notes Zhang."We anticipate that with more precise fabrication, our technique should also yield a true invisibility carpet that works in the microwave and visible parts of the spectrum and at a larger size -- showing promise for many futuristic defense and other applications."

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Super-Small Transistor Created: Artificial Atom Powered by Single Electrons

The researchers report inNature Nanotechnologythat the transistor's central component -- an island only 1.5 nanometers in diameter -- operates with the addition of only one or two electrons. That capability would make the transistor important to a range of computational applications, from ultradense memories to quantum processors, powerful devices that promise to solve problems so complex that all of the world's computers working together for billions of years could not crack them.

In addition, the tiny central island could be used as an artificial atom for developing new classes of artificial electronic materials, such as exotic superconductors with properties not found in natural materials, explained lead researcher Jeremy Levy, a professor of physics and astronomy in Pitt's School of Arts and Sciences. Levy worked with lead author and Pitt physics and astronomy graduate student Guanglei Cheng, as well as with Pitt physics and astronomy researchers Feng Bi, Daniela Bogorin,and Cheng Cen. The Pitt researchers worked with a team from the University of Wisconsin at Madison led by materials science and engineering professor Chang-Beom Eom, including research associates Chung Wun Bark, Jae-Wan Park, and Chad Folkman. Also part of the team were Gilberto Medeiros-Ribeiro, of HP Labs, and Pablo F. Siles, a doctoral student at the State University of Campinas in Brazil.

Levy and his colleagues named their device SketchSET, or sketch-based single-electron transistor, after a technique developed in Levy's lab in 2008 that works like a microscopic Etch A Sketch^TM, the drawing toy that inspired the idea. Using the sharp conducting probe of an atomic force microscope, Levy can create such electronic devices as wires and transistors of nanometer dimensions at the interface of a crystal of strontium titanate and a 1.2 nanometer thick layer of lanthanum aluminate. The electronic devices can then be erased and the interface used anew.

The SketchSET -- which is the first single-electron transistor made entirely of oxide-based materials -- consists of an island formation that can house up to two electrons. The number of electrons on the island -- which can be only zero, one, or two -- results in distinct conductive properties. Wires extending from the transistor carry additional electrons across the island.

One virtue of a single-electron transistor is its extreme sensitivity to an electric charge, Levy explained. Another property of these oxide materials is ferroelectricity, which allows the transistor to act as a solid-state memory. The ferroelectric state can, in the absence of external power, control the number of electrons on the island, which in turn can be used to represent the 1 or 0 state of a memory element. A computer memory based on this property would be able to retain information even when the processor itself is powered down, Levy said. The ferroelectric state also is expected to be sensitive to small pressure changes at nanometer scales, making this device potentially useful as a nanoscale charge and force sensor.

The research inNature Nanotechnologyalso was supported in part by grants from the U.S. Defense Advanced Research Projects Agency (DARPA), the U.S. Army Research Office, the National Science Foundation, and the Fine Foundation.

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Carbon Fiber Used to Reinforce Buildings; Protect from Explosion

Sarah Orton, assistant professor of civil engineering in the MU College of Engineering, has focused on using carbon fiber reinforced polymer (CFRP), a fabric that can carry 143,000 pounds of force per square inch and has various applications to strengthen reinforced concrete buildings. CFRP has been used previously to strengthen buildings for earthquakes.

"CFRP has been used in places like California since the 1980s to protect buildings from earthquakes, but it has so many applications," Orton said."Now, we have to worry about damage caused by attacks. This fabric can be a great tool to protect people in threatened buildings."

To protect a building from an extreme event, CFRP can be used to increase the bending capacity of walls or columns. Previously, Orton invented an anchor that can be embedded in the column or joint to make CFRP more effective. In that work, Orton found that the anchors allow the CFRP to reach its full tension strength rather than separating from the concrete at only about half its strength.

CFRP can be used to protect an entire wall from an explosion. To study the effectiveness of different ways of applying CFRP, Orton worked with the U.S. Army Engineer Research and Development Center (ERDC) to detonate explosives near CFRP-reinforced concrete slabs. She found that CFRP, when layered and anchored, provided a significant amount of protection. However, she said that applying additional protection to the front of the concrete slab, such as a steel plate, would enhance the slab's performance.

Orton says the high costs of approximately$30 per square foot have kept CFRP from being widely implemented in non-earthquake prone areas.

"This is a really useful material," Orton said."I continue to be fascinated by the material's strength and applications. Retrofitting buildings with CFRP will help protect people from attacks and potentially collapse of the building."

The study,"Use of Carbon Fiber Anchors to Improve Performance of CFRP Strengthened Concrete Structures Subjected to Blast and Impact Loads," will be published in a special publication of the American Concrete Institute.

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NASA Announces New Homes for Shuttle Orbiters After Retirement

NASA Administrator Charles Bolden on April 12, 2011 announced the facilities where four shuttle orbiters will be displayed permanently at the conclusion of the Space Shuttle Program. Shuttle Enterprise, the first orbiter built, will move from the Smithsonian's National Air and Space Museum Steven F. Udvar-Hazy Center in Virginia to the Intrepid Sea, Air& Space Museum in New York. The Udvar-Hazy Center will become the new home for shuttle Discovery, which retired after completing its 39th mission in March. Shuttle Endeavour, which is preparing for its final flight at the end of the month, will go to the California Science Center in Los Angeles. Atlantis, which will fly the last planned shuttle mission in June, will be displayed at the Kennedy Space Center Visitor Complex in Florida.

"We want to thank all of the locations that expressed an interest in one of these national treasures," Bolden said."This was a very difficult decision, but one that was made with the American public in mind. In the end, these choices provide the greatest number of people with the best opportunity to share in the history and accomplishments of NASA's remarkable Space Shuttle Program. These facilities we've chosen have a noteworthy legacy of preserving space artifacts and providing outstanding access to U.S. and international visitors."

NASA also announced that hundreds of shuttle artifacts have been allocated to museums and education institutions.

• Various shuttle simulators for the Adler Planetarium in Chicago, the Evergreen Aviation& Space Museum of McMinnville, Ore., and Texas A&M's Aerospace Engineering Department
• Full fuselage trainer for the Museum of Flight in Seattle
• Nose cap assembly and crew compartment trainer for the National Museum of the U.S. Air Force at Wright-Patterson Air Force Base in Ohio
• Flight deck pilot and commander seats for NASA's Johnson Space Center in Houston
• Orbital maneuvering system engines for the U.S. Space and Rocket Center of Huntsville, Ala., National Air and Space Museum in Washington, and Evergreen Aviation& Space Museum

For more information about NASA's placement of the space shuttle orbiters, visit:http://www.nasa.gov/transition

For information about the Space Shuttle Program, visit:http://www.nasa.gov/shuttle

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Lights and Flat-Panel Displays: Researchers 'Brighten' the Future of Organic Light-Emitting Diode Technology

In the case of Organic Light-Emitting Diode (OLED) devices, it most certainly can. Primary researchers Michael G. Helander (PhD Candidate and Vanier Canada Graduate Scholar), Zhibin Wang (PhD Candidate), and led by Professor Zheng-Hong Lu of the Department of Materials Science& Engineering at the University of Toronto, have found a simple method of using chlorine to drastically reduce traditional OLED device complexity and dramatically improve its efficiency all at the same time. By engineering a one-atom thick sheet of chlorine onto the surface of an existing industry-standard electrode material (indium tin oxide, ITO) found in today's flat-panel displays, these researchers have created a medium that allows for efficient electrical transport while eliminating the need for several costly layers found in traditional OLED devices.

"It turns out that it's remarkably easy to engineer this one-atom thick layer of chlorine onto the surface of ITO," says Helander."We developed a UV light assisted process to achieve chlorination, which negates the need for chlorine gas, making the entire procedure safe and reliable."

The team tested their green-emitting"Cl-OLED" against a conventional OLED and found that the efficiency was more than doubled at very high brightness."OLEDs are known for their high-efficiency," says Helander."However, the challenge in conventional OLEDs is that as you increase the brightness, the efficiency drops off rapidly."

Using their chlorinated ITO, this team of advanced materials researchers found that they were able to prevent this drop off and achieve a record efficiency of 50% at 10,000 cd/m2 (a standard florescent light has a brightness of approximately 8,000 cd/m2), which is at least two times more efficient than the conventional OLED.

"Our Cl-ITO eliminates the need for several stacked layers found in traditional OLEDs, reducing the number of manufacturing steps and equipment, which ultimately cuts down on the costs associated with setting up a production line," says Professor Zheng-Hong Lu.

"This effectively lowers barriers for mass production and thereby accelerates the adoption of OLED devices into mainstream flat-panel displays and other lighting technologies."

The results of this work are published online in the journalScienceon April 14, 2011.

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Rainbow-Trapping Scientist Now Strives to Slow Light Waves Even Further

In a paper published March 29 in theProceedings of the National Academy of Sciences, Qiaoqiang Gan (pronounced"Chow-Chung" and"Gone"), PhD, an assistant professor of electrical engineering at the University at Buffalo's School of Engineering and Applied Sciences, and his colleagues at Lehigh University, where he was a graduate student, described how they slowed broadband light waves using a type of material called nanoplasmonic structures.

Gan explains that the ultimate goal is to achieve a breakthrough in optical communications called multiplexed, multiwavelength communications, where optical data can potentially be tamed at different wavelengths, thus greatly increasing processing and transmission capacity.

He notes that it is widely recognized that if light could ever be stopped entirely, new possibilities would open up for data storage.

"At the moment, processing data with optical signals is limited by how quickly the signal can be interpreted," he says."If the signal can be slowed, more information could be processed without overloading the system."

Gan and his colleagues created nanoplasmonic structures by making nanoscale grooves in metallic surfaces at different depths, which alters the materials' optical properties.

These plasmonic chips provide the critical connection between nanoelectronics and photonics, Gan explains, allowing these different types of devices to be integrated, a prerequisite for realizing the potential of optical computing,"lab-on-a-chip" biosensors and more efficient, thin-film photovoltaic materials.

According to Gan, the optical properties of the nanoplasmonic structures allow different wavelengths of light to be trapped at different positions in the structure, potentially allowing for optical data storage and enhanced nonlinear optics.

The structures Gan developed slow light down so much that they are able to trap multiple wavelengths of light on a single chip, whereas conventional methods can only trap a single wavelength in a narrow band.

"Light is usually very fast, but the structures I created can slow broadband light significantly," says Gan."It's as though I can hold the light in my hand."

That, Gan explains, is because of the structures' engineered surface"plasmon resonances," where light excites the waves of electrons that oscillate back and forth on metal surfaces.

In this case, he says, light can be slowed down and trapped in the vicinity of resonances in this novel, dispersive structural material.

Gan and his colleagues also found that because the nanoplasmonic structures they developed can trap very slow resonances of light, they can do so at room temperature, instead of at the ultracold temperatures that are required in conventional slow-light technologies.

"In the PNAS paper, we showed that we trapped red to green," explains Gan."Now we are working on trapping a broader wavelength, from red to blue. We want to trap the entire rainbow."

Gan, who was hired at UB under the UB 2020 strategic strength in Integrated Nanostructured Systems, will be working toward that goal, using the ultrafast light source in UB's Department of Electrical Engineering in the laboratory of UB professor and vice president for research Alexander N. Cartwright.

"This ultrafast light source will allow us to measure experimentally just how slow is the light that we have trapped in our nanoplasmonic structures," Gan explains."Once we know that, we will be able to demonstrate our capability to manipulate light through experiments and optimize the structure to slow the light further."

Co-authors with Gan on the study are Filbert Bertoli, Yongkang Gao, Yujie Ding, Kyle Wagner and Dmitri Vezenov, all of Lehigh University.

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New Fracture Resistance Mechanisms Provided by Graphene

The research, lead by Assistant Professor Erica L. Corral from the Materials Science and Engineering Department at the University of Arizona in Tucson, and Professor Nikhil Koratkar from the Department of Mechanical, Aerospace and Nuclear Engineering at Rensselaer Polytechnic Institute in Troy, New York, was recently published inACS Nano, the monthly journal of the American Chemical Society.

"Our work on graphene ceramic composites is the first of its kind in the open literature and shows mechanisms for toughening using two-dimensional graphene sheets that have yet to be seen in ceramic composites," said Corral."We have significantly increased the toughness of a ceramic and made the first observations of graphene that arrest crack propagation and force the crack to change directions in not just two but also three dimensions."

These observations will lead to a new approach for composite design using graphene in ceramics that has not been possible using conventional fiber reinforcements, says Corral."The high surface area and unique two-dimensional sheet geometry seem to be better at arresting crack growth in ceramics over conventional fibers that are one-dimensional reinforcements," she said.

"This is a classic example of highly successful interdisciplinary research across universities that was unheard of 15 or 20 years ago, but is now becoming critically important if we are to continue to make breakthrough discoveries and maintain the competiveness of the United States in the 21st century," said Prof. Koratkar of the Rensselaer Polytechnic Institute. Koratkar met Dr. Corral at a National Science Foundation-sponsored nanoscience conference where she delivered a talk on her work in carbon nanotube ceramic composites.

Koratkar was impressed with Corral's presentation, and approached her regarding the possibility of exploring the use of graphene to increase toughening in brittle ceramics."Over the next year we leveraged my lab's expertise in the synthesis of bulk quantities of graphene platelets and the expertise of Corral's group in ceramic composite fabrication and testing," Koratkar said."Our results published inACS Nanoshow the tremendous promise that graphene shows in toughening ceramics that are notoriously brittle and prone to failure. This work could open up an entirely new graphene ceramic nanocomposites field of study," he says.

This is the first published work describing the use of graphene nanofiller to reinforce ceramics and will appear in the journalACS Nano. This discovery -- measured to increase fracture resistance of the resulting ceramic nanocomposite by over 200 percent -- could potentially be used to enhance toughness for a range of ceramic materials, enabling their widespread use in high-performance, structural applications that require operating temperatures greater than 1,000 degrees Celsius while maintaining structural integrity.

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Tissue Engineers Use New System to Measure Biomaterials, Structures

The research appears online in theProceedings of the National Academy of Sciences.

In addition to helping engineers evaluate how quickly and stably different cell types will combine into desired structures, the power measurements could also improve scientists' understanding of natural tissue growth, such as in fetal development, and how cancerous cells sometimes break off from a tumor and travel in the body, said Jeffrey Morgan, the paper's senior author and associate professor of medical science in Brown's Department of Molecular Pharmacology, Physiology and Biotechnology.

"Cells are the ultimate building parts, and it's important to understand how they are held together, how they assemble together and the energies with which they do that, if you want to delve into the field of tissue engineering," said Morgan, who last year co-developed the first artificial human ovary."Sometimes these complex processes go wrong, and that's where it's relevant to cancer in terms of cell-to-cell adhesion. But it also plays out very nicely in developmental biology where a very complex 3-D orchestration of cell movement and forces gives rise to new tissues and organs."

Climb the cone

In the system, the researchers deposited cells in very small wells made of a specially designed hydrogel. The wells each have a cone of different steepness rising in the middle, like Bundt cake pans do. The cells form a doughnut shape around the cone. The mutual attraction of the cells then causes the doughnut of living cells to slide up the cone while a video microscope watches. The observed rate at which this mass of cells overcomes the force of gravity to ascend the cone yields a valuable number for the overall power exerted by the cells.

"There's no need to calibrate this device, because gravity is consistent and reliable and there are no moving parts other than the living cells," Morgan said.

Such overall measures of energy, time, and power have been hard to obtain, said lead author and doctoral candidate Jacquelyn Youssef. Many scientists have studied distinct forces and energies within and among cells, such as the bonding strength between particular proteins, but such measures leave tissue engineers to estimate the total energy in a structure by adding up what's known about the cells, related proteins, and their many interactions.

"What we've developed looks at all these things in this one system together," Youssef said."There's lots of moving parts."

At the same time as it offers an aggregate measure, the system allows for teasing out the relative contributions of those moving parts. In their experiments, the team, which also included Lambert Freund, professoremeritusof engineering at Brown, and recent Ph.D. graduate Asha Nurse, used a drug treatment to inhibit the contractions cells use to"grab" each other. They found that among human skin fibroblast cells, eliminating that particular action took away about half of the total power of the doughnut structure formation.

The researchers worked with two types of cells in the paper. In addition to human skin fibroblasts, which aggregated and ascended the cones in a couple of hours, they also tested liver cells, which took days to reach the same peaks.

Morgan said the system will work for many other cell types and even mixtures of cells as well, making it a promising instrument for assessing the structural characteristics of the variety of building materials that tissue engineers might choose to use in their structures. Bioengineers can also use it to measure the effect different chemicals or drugs might have on the rate or energy of tissue formation.

"What we're driving at is an understanding of how cells will spontaneously form these three-dimensional structures," Morgan said."The rate at which they do that is important to understanding how to design something more complex."

Funding for the research came from the National Science Foundation and the National Institutes of Health.

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Search for Advanced Materials Aided by Discovery of Hidden Symmetries in Nature

The research is expected to have broad relevance in many development efforts involving physical, chemical, biological, or engineering disciplines including, for example, the search for advanced ferroelectric ferromagnet materials for next-generation ultrasound devices and computers. The paper describing the research will be posted early online by the journal on 3 April 2011, prior to its publication in the journal's May 2011 print edition.

Before the publication of this paper, scientists and engineers had five different types of symmetries to use as tools for understanding the structures of materials whose building blocks are arranged in fairly regular patterns. Four types of symmetries had been known for thousands of years -- called rotation, inversion, rotation inversion, and translation -- and a fifth type -- called time reversal -- had been discovered about 60 years ago. Now, Gopalan and Litvin have added a new, sixth, type, called rotation reversal. As a result, the number of known ways in which the components of such crystalline materials can be combined in symmetrical ways has multiplied from no more than 1,651 before to more than 17,800 now."We mathematically combined the new rotation-reversal symmetry with the previous five symmetries and now we know that symmetrical groups can form in crystalline materials in a much larger number of ways," said Daniel B. Litvin, distinguished professor of physics, who coauthored the study with Venkatraman Gopalan, professor of materials science and engineering.

The new rotation-reversal symmetry enriches the mathematical language that researchers use to describe a crystalline material's structure and to predict its properties."Rotation reversal is an absolutely new approach that is different in that it acts on a static component of the material's structure, not on the whole structure all at once," Litvin said."It is important to look at symmetries in materials because symmetry dictates all natural laws in our physical universe."

The most simple type of symmetry -- rotation symmetry -- is obvious, for example, when a square shape is rotated around its center point: the square shows its symmetrical character by looking exactly the same at four points during the rotation: at 90 degrees, 180 degrees, 270 degrees, and 360 degrees. Gopalan and Litvin say their new rotation-reversal symmetry is obvious, as well, if you know where to look.

The"eureka moment" of the discovery occurred when Gopalan recognized that the simple concept of reversing the direction of a spiral-shaped structure from clockwise to counterclockwise opens the door to a distinctly new type of symmetry. Just as a square shape has the quality of rotation symmetry even when it is not being rotated, Gopalan realized that a spiral shape has the quality of rotation-reversal symmetry even when it is not being physically forced to rotate in the reverse direction. Their further work with this rotation-reversal concept revealed many more structural symmetries than previously had been recognized in materials containing various types of directionally oriented structures. Many important biological molecules, for example, are said to be either"right handed" or"left handed," including DNA, sugars, and proteins.

"We found that rotation-reversal symmetry also exists in paired structures where the partner components lean toward each other, then away from each other in paired patterns symmetrically throughout a material," Gopalan said. These"tilting octahedral" structures are common in a wide variety of crystalline materials, where all the component structures are tightly interconnected by networks of shared atoms. The researchers say it is possible that components of materials with rotation-reversal symmetry could be engineered to function as on/off switches for a variety of novel applications.

The now-much-larger number of possible symmetry groups also is expected to be useful in identifying materials with unusual combinations of properties."For example, the goal in developing a ferroelectric ferromagnet is to have a material in which the electrical dipoles and the magnetic moments coexist and are coupled in the same material -- that is, a material that allows electrical control of magnetism -- which would be very useful to have in computers," Gopalan said. The addition of rotation-reversal symmetry to the materials-science toolbox may help researchers to identify and search for structures in materials that could have strong ferroelectric and ferromagnetic properties.

Gopalan and Litvin said a goal of their continuing research is to describe each of the more than 17,800 different combinations of the six symmetry types to give materials scientists a practical new tool for significantly increasing the efficiency and effectiveness in finding novel materials. The team also plans to conduct laboratory experiments that make use of their theoretical work on rotation-reversal symmetry."We have done some predictions, we will test those predictions experimentally," Litvin said."We are in the very early stages of implementing the results we have described in our new theory paper." Gopalan said, for example, that he has predicted new forms for optical properties in the commonplace quartz crystals that are used widely in watches and electronic equipment, and that his group now is testing these predictions experimentally.

The National Science Foundation provided financial support for this research through its Materials Research Science and Engineering Centers program.

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Scientists Develop New Technology for Stroke Rehabilitation

In a paper to be presented this week (6 April) at the Institution of Engineering and Technology (IET) Assisted Living Conference, Dr Geoff Merrett, a lecturer in electronic systems and devices, will describe the design and evaluation of three technologies which could help people who are affected by stroke to regain movement in their hand and arm.

Dr Merrett worked with Dr Sara Demain, a lecturer in physiotherapy and Dr Cheryl Metcalf, a researcher in electronic systems and devices, to develop three 'tactile' devices which generate a realistic 'sense of touch' and sensation -- mimicking those involved in everyday activities.

Dr Demain says:"Most stroke rehabilitation systems ignore the role of sensation and they only allow people repetitive movement. Our aim is to develop technology which provides people with a sense of holding something or of feeling something, like, for example, holding a hot cup of tea, and we want to integrate this with improving motor function."

Three tactile devices were developed and tested on patients who had had a stroke and on healthy participants. The devices were: a 'vibration' tactile device, which users felt provided a good indication of touch but did not really feel as if they were holding anything; a 'motor-driven squeezer' device, which users said felt like they were holding something, a bit like catching a ball; and a 'shape memory alloy' device which has thermal properties and creates a sensation like picking up a cup of tea.

Dr Merrett adds:"We now have a number of technologies, which we can use to develop sensation. This technology can be used on its own as a stand-alone system to help with sensory rehabilitation or it could be used alongside existing health technologies such as rehabilitation robots or gaming technologies which help patient rehabilitation."

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New Research Advances Understanding of Lead Selenide Nanowires

Now, a research team at the University of Pennsylvania's schools of Engineering and Applied Science and Arts and Sciences has shown how to control the characteristics of semiconductor nanowires made of a promising material: lead selenide.

Led by Cherie Kagan, professor in the departments of Electrical and Systems Engineering, Materials Science and Engineering and Chemistry and co-director of Pennergy, Penn's center focused on developing alternative energy technologies, the team's research was primarily conducted by David Kim, a graduate student in the Materials Science and Engineering program.

The team's work was published online in the journalACS Nanoand will be featured in the Journal's April podcast.

The key contribution of the team's work has to do with controlling the conductive properties of lead selenide nanowires in circuitry. Semiconductors come in two types,nandp, referring to the negative or positive charge they can carry. The ones that move electrons, which have a negative charge, are called"n-type." Their"p-type" counterparts don't move protons but rather the absenceof an electron -- a"hole" -- which is the equivalent of moving a positive charge.

Before they are integrated into circuitry, the semiconductor nanowire must be"wired up" into a device. Metal electrodes must be placed on both ends to allow electricity to flow in and out; however, the"wiring" may influence the observed electrical characteristics of the nanowires, whether the device appears to ben-type orp-type. Contamination, even from air, can also influence the device type. Through rigorous air-free synthesis, purification and analysis, they kept the nanowires clean, allowing them to discover the unique properties of these lead selenide nanomaterials.

Researchers designed experiments allowing them to separate the influence of the metal"wiring" on the motion of electrons and holes from that of the behavior intrinsic to the lead selenide nanowires. By controlling the exposure of the semiconductor nanowire device to oxygen or the chemical hydrazine, they were able to change the conductive properties betweenp-type andn-type. Altering the duration and concentration of the exposure, the nanowire device type could be flipped back and forth.

"If you expose the surfaces of these structures, which are unique to nanoscale materials, you can make themp-type, you can make themn-type, and you can make them somewhere in between, where it can conduct both electrons and holes," Kagan said."This is what we call 'ambipolar.'"

Devices combining onen-type and onep-type semiconductor are used in many high-tech applications, ranging from the circuits of everyday electronics, to solar cells and thermoelectrics, which can convert heat into electricity.

"Thinking about how we can build these things and take advantage of the characteristics of nanoscale materials is really what this new understanding allows," Kagan said.

Figuring out the characteristics of nanoscale materials and their behavior in device structures are the first steps in looking forward to their applications.

These lead selenide nanowires are attractive because they may be synthesized by low-cost methods in large quantities.

"Compared to the big machinery you need to make other semiconductor devices, it's significantly cheaper," Kagan said."It doesn't look much more complicated than the hoods people would recognize from when they had to take chemistry lab."

In addition to the low cost, the manufacturing process for lead selenide nanowires is relatively easy and consistent.

"You don't have to go to high temperatures to get mass quantities of these high-quality lead selenide nanowires," Kim said."The techniques we use are high yield and high purity; we can use all of them."

And because the conductive qualities of the lead selenide nanowires can be changed while they are situated in a device, they have a wider range of functionality, unlike traditional silicon semiconductors, which must first be"doped" with other elements to make them"p" or"n."

The Penn team's work is a step toward integrating these nanomaterials in a range of electronic and optoelectronic devices, such as photo sensors.

The research was conducted by Kim and Kagan, along with Materials Science and Engineering undergraduate and graduate students Tarun R. Vemulkar and Soong Ju Oh; Weon-Kyu Koh, a graduate student in Chemistry; and Christopher B. Murray, a professor in Chemistry and in Materials Science and Engineering.

This work was supported with funding from the National Science Foundation Division of Materials Research, the National Science Foundation Solar Program and the National Science Foundation Nano-Bio Interface Center.

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Micro Aircraft Improves Avionic Systems and Sensors

A particularly important feature of the novel design is its modular construction. This allows the scientists to install a wide variety of systems to be tested under flight conditions. This also applies to components of the electric propulsion unit, since the scientists intend to use IMPULLS to investigate possible implementations of electric and hybrid propulsion systems in aircraft.

UAVs like IMPULLS are ideal for measuring atmospheric pollution, for aerial geo-surveying or monitoring the environment and infrastructures from above. A further field of deployment is information collection in emergencies and dangerous situations. Appropriately equipped UAVs can also be deployed in adverse weather conditions or hazardous situations that would pose an unreasonable risk to pilots.

"Thanks to advances in miniaturization and improved performance of sensor and avionics systems, we can use IMPULLS as a cornerstone for these kind of developments," says Professor Mirko Hornung, chair of the Institute of Aircraft Design. Deriving and understanding the associated business models and ranges of services are also topics that can be investigated using the IMPULLS platform.

IMPULLS has a wingspan of 5 meters and an empty weight of 20 kilograms. It is propelled by a two-kilowatt electric motor. The UAV can carry a payload of 10 kilograms and fly non-stop for up to 75 minutes. As in commercial aircraft, essential safety-relevant components are designed redundantly.

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Nano Fitness: Helping Enzymes Stay Active and Keep in Shape

One key challenge is the stability of enzymes, a particular type of protein that speeds up, or catalyzes, chemical reactions. Taken out of their natural environment in the cell or body, enzymes can quickly lose their shape and denature. Everyday examples of enzymes denaturing include milk going sour, or eggs turning solid when boiled.

Rensselaer Polytechnic Institute Professor Marc-Olivier Coppens has developed a new technique for boosting the stability of enzymes, making them useful under a much broader range of conditions. Coppens confined lysozyme and other enzymes inside carefully engineered nanoscale holes, or nanopores. Instead of denaturing, these embedded enzymes mostly retained their 3-D structure and exhibited a significant increase in activity.

"Normally, when you put an enzyme on a surface, its activity goes down. But in this study, we discovered that when we put enzymes in nanopores -- a highly controlled environment -- the enzymatic activity goes up dramatically," said Coppens, a professor in the Department of Chemical and Biological Engineering at Rensselaer."The enzymatic activity turns out to be very dependent on the local environment. This is very exciting."

Results of the study were published last month by the journalPhysical Chemistry Chemical Physics.

Researchers at Rensselaer and elsewhere have made important discoveries by wrapping enzymes and other proteins around nanomaterials. While this immobilizes the enzyme and often results in high stability and novel properties, the enzyme's activity decreases as it loses its natural 3-D structure.

Coppens took a different approach, and inserted enzymes inside nanopores. Measuring only 3-4 nanometers (nm) in size, the enzyme lysozyme fits snugly into a nanoporous material with well-controlled pore size between 5 nm and 12 nm. Confined to this compact space, the enzymes have a much harder time unfolding or wiggling around, Coppens said.

The discovery raises many questions and opens up entirely new possibilities related to biology, chemistry, medicine, and nanoengineering, Coppens said. He envisions this technology could be adapted to better control nanoscale environments, as well as increase the activity and selectivity of different enzymes. Looking forward, Coppens and colleagues will employ molecular simulations, multiscale modeling methods, and physical experiments to better understand the fundamental mechanics of confining enzymes inside nanopores.

The study was co-authored by Lung-Ching Sang, a former Rensselaer graduate student in the Department of Chemical and Biological Engineering.

This research was supported by the National Science Foundation, via the Nanoscale Science and Engineering Center for Directed Assembly of Nanostructures at Rensselaer. The project was also supported by the International Center for Materials Nanoarchitectonics of the National Institute for Materials Science, Japan.

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Third Dimension of Specific Cell Cultivation

So far, several approaches have been used to cell culture in three-dimensional environments which are mostly produced from agarose, collagen fibers or matrigel. They are to simulate the flexible three-dimensional reality in which the cells act normally and, hence, allow for more realistic experiments than those using cell cultures in"two-dimensional Petri dishes." All approaches used so far have one common feature: They are mostly heterogeneous with random pore sizes. They have hardly been characterized structurally and biochemically.

It was the objective of the group under the direction of Bastmeyer to develop defined three-dimensional growth substrates for the cell culture. The cells are to adhere at certain points only rather than randomly. In this way, parameters, such as the cell shape, cell volume, intercellular force development, or cellular differentiation can be determined systematically as a function of the external geometry of the surroundings. These findings are needed for the later specific larger-scale production of three-dimensional growth environments for tissue cultures required in regenerative medicine, for instance.

This objective was reached by means of a special polymer scaffold. The scaffold consists of a flexible, protein-repellent polymer with small box-shaped holds made of a protein-binding material. For scaffold construction, the scientists used the Direct Laser Writing Method (DLS) developed by the physicists Professor Martin Wegener and Professor Georg von Freymann at CFN. By means of this process, the protein-repellent structure was fabricated. It consists of 25µm high pillars that are connected by thin bars at various heights. In a second lithography step, the holds were placed exactly in the middle of the bars. With the help of a solution of adhesion proteins, the proteins only bind to these small holds. Within two hours, individual cells colonize the scaffolds and adhere to the given adhesion points only.

For the first time, the scientists of CFN, Karlsruhe, succeeded in producing suitable materials, in which the growth of individual cells can be controlled and manipulated specifically in three dimensions. This is an important step towards the general understanding of how the natural three-dimensional environment in the tissue influences the behavior of cells.

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Self-Cooling Observed in Graphene Elctronics

Led by mechanical science and engineering professor William King and electrical and computer engineering professor Eric Pop, the team will publish its findings in the April 3 advance online edition of the journalNature Nanotechnology.

The speed and size of computer chips are limited by how much heat they dissipate. All electronics dissipate heat as a result of the electrons in the current colliding with the device material, a phenomenon called resistive heating. This heating outweighs other smaller thermoelectric effects that can locally cool a device. Computers with silicon chips use fans or flowing water to cool the transistors, a process that consumes much of the energy required to power a device.

Future computer chips made out of graphene -- carbon sheets 1 atom thick -- could be faster than silicon chips and operate at lower power. However, a thorough understanding of heat generation and distribution in graphene devices has eluded researchers because of the tiny dimensions involved.

The Illinois team used an atomic force microscope tip as a temperature probe to make the first nanometer-scale temperature measurements of a working graphene transistor. The measurements revealed surprising temperature phenomena at the points where the graphene transistor touches the metal connections. They found that thermoelectric cooling effects can be stronger at graphene contacts than resistive heating, actually lowering the temperature of the transistor.

"In silicon and most materials, the electronic heating is much larger than the self-cooling," King said."However, we found that in these graphene transistors, there are regions where the thermoelectric cooling can be larger than the resistive heating, which allows these devices to cool themselves. This self-cooling has not previously been seen for graphene devices."

This self-cooling effect means that graphene-based electronics could require little or no cooling, begetting an even greater energy efficiency and increasing graphene's attractiveness as a silicon replacement.

"Graphene electronics are still in their infancy; however, our measurements and simulations project that thermoelectric effects will become enhanced as graphene transistor technology and contacts improve" said Pop, who is also affiliated with the Beckman Institute for Advanced Science, and the Micro and Nanotechnology Laboratory at the U. of I.

Next, the researchers plan to use the AFM temperature probe to study heating and cooling in carbon nanotubes and other nanomaterials.

King also is affiliated with the department of materials science and engineering, the Frederick Seitz Materials Research Laboratory, the Beckman Institute, and the Micro and Nanotechnology Laboratory.

The Air Force Office of Scientific Research and the Office of Naval Research supported this work. Co-authors of the paper included graduate student Kyle Grosse, undergraduate Feifei Lian and postdoctoral researcher Myung-Ho Bae.

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First Macro-Scale Thin-Film Solid-Oxide Fuel Cell: Strong, Nanostructured Membrane Enables Scaling for Clean-Energy Applications

While SOFCs have previously worked at the micro-scale, this is the first time any research group has overcome the structural challenges of scaling the technology up to a practical size with a proportionally higher power output.

Reported online April 3 inNature Nanotechnology, the demonstration of this fully functional SOFC indicates the potential of electrochemical fuel cells to be a viable source of clean energy.

"The breakthrough in this work is that we have demonstrated power density comparable to what you can get with tiny membranes, but with membranes that are a factor of a hundred or so larger, demonstrating that the technology is scalable," says principal investigator Shriram Ramanathan, Associate Professor of Materials Science at SEAS.

SOFCs create electrical energy via an electrochemical reaction that takes place across an ultra-thin membrane. This 100-nanometer membrane, comprising the electrolyte and electrodes, has to be thin enough to allow ions to pass through it at a relatively low temperature (which, for ceramic fuel cells, lies in the range of 300 to 500 degrees Celsius). These low temperatures allow for a quick start-up, a more compact design, and less use of rare-earth materials.

So far, however, thin films have been successfully implemented only in micro-SOFCs, where each chip in the fuel cell wafer is about 100 microns wide. For practical applications, such as use in compact power sources, SOFCs need to be about 50 times wider.

The electrochemical membranes are so thin that creating one on that scale is roughly equivalent to making a 16-foot-wide sheet of paper. Naturally, the structural issues are significant.

"If you make a conventional thin membrane on that scale without a support structure, you can't do anything -- it will just break," says co-author Bo-Kuai Lai, a postdoctoral fellow at SEAS."You make the membrane in the lab, but you can't even take it out. It will just shatter."

With lead author Masaru Tsuchiya (Ph.D. '09), a former member of Ramanathan's lab who is now at SiEnergy, Ramanathan and Lai fortified the thin film membrane using a metallic grid that looks like nanoscale chicken wire.

The tiny metal honeycomb provides the critical structural element for the large membrane while also serving as a current collector. Ramanathan's team was able to manufacture membrane chips that were 5 mm wide, combining hundreds of these chips into palm-sized SOFC wafers.

While other researchers' earlier attempts at implementing the metallic grid showed structural success, Ramanathan's team is the first to demonstrate a fully functional SOFC on this scale. Their fuel cell's power density of 155 milliwatts per square centimeter (at 510 degrees Celsius) is comparable to the power density of micro-SOFCs.

When multiplied by the much larger active area of this new fuel cell, that power density translates into an output high enough for relevance to portable power.

Previous work in Ramanathan's lab has developed micro-SOFCs that are all-ceramic or that use methane as the fuel source instead of hydrogen. The researchers hope that future work on SOFCs will incorporate these technologies into the large-scale fuel cells, improving their affordability.

In the coming months, they will explore the design of novel nanostructured anodes for hydrogen-alternative fuels that are operable at these low temperatures and work to enhance the microstructural stability of the electrodes.

The research was supported in part by the National Science Foundation (NSF) and performed in part at the Harvard University Center for Nanoscale Systems, a member of the NSF-funded National Nanotechnology Infrastructure Network.

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