Faster Computers, Electronic Devices Possible After Scientists Create Large-area Graphene On Copper

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ScienceDaily (May 7, 2009) — The creation of large-area graphene using copper may enable the manufacture of new graphene-based devices that meet the scaling requirements of the semiconductor industry, leading to faster computers and electronics, according to a team of scientists and engineers at The University of Texas at Austin.

"Graphene could lead to faster computers that use less power, and to other sorts of devices for communications such as very high-frequency (radio-frequency-millimeter wave) devices," said Professor and physical chemist Rod Ruoff, one of the corresponding authors on the Science article. "Graphene might also find use as optically transparent and electrically conductive films for image display technology and for use in solar photovoltaic electrical power generation."
Graphene, an atom-thick layer of carbon atoms bonded to one another in a "chickenwire" arrangement of hexagons, holds great potential for nanoelectronics, including memory, logic, analog, opto-electronic devices and potentially many others. It also shows promise for electrical energy storage for supercapacitors and batteries, for use in composites, for thermal management, in chemical-biological sensing and as a new sensing material for ultra-sensitive pressure sensors.
"There is a critical need to synthesize graphene on silicon wafers with methods that are compatible with the existing semiconductor industry processes," Ruoff said. "Doing so will enable nanoelectronic circuits to be made with the exceptional efficiencies that the semiconductor industry is well known for."
Graphene can show very high electron- and hole-mobility; as a result, the switching speed of nanoelectronic devices based on graphene can in principle be extremely high. Also, graphene is "flat" when placed on a substrate (or base material) such as a silicon wafer and, thus, is compatible with the wafer-processing approaches of the semiconductor industry. The exceptional mechanical properties of graphene may also enable it to be used as a membrane material in nanoelectromechanical systems, as a sensitive pressure sensor and as a detector for chemical or biological molecules or cells.
The university researchers, including post-doctoral fellow Xuesong Li, and Luigi Colombo, a TI Fellow from Texas Instruments, Inc., grew graphene on copper foils whose area is limited only by the furnace used. They demonstrated for the first time that centimeter-square areas could be covered almost entirely with mono-layer graphene, with a small percentage (less than five percent) of the area being bi-layer or tri-layer flakes. The team then created dual-gated field effect transistors with the top gate electrically isolated from the graphene by a very thin layer of alumina, to determine the carrier mobility. The devices showed that the mobility, a key metric for electronic devices, is significantly higher than that of silicon, the principal semiconductor of most electronic devices, and comparable to natural graphite.
"We used chemical-vapor deposition from a mixture of methane and hydrogen to grow graphene on the copper foils," said Ruoff. "The solubility of carbon in copper being very low, and the ability to achieve large grain size in the polycrystalline copper substrate are appealing factors for its use as a substrate --along with the fact that the semiconductor industry has extensive experience with the use of thin copper films on silicon wafers. By using a variety of characterization methods we were able to conclude that growth on copper shows significant promise as a potential path for high quality graphene on 300-millimeter silicon wafers."
The university's effort was funded in part by the state of Texas, the South West Academy for Nanoelectronics (SWAN) and the DARPA CERA Center. Electrical and computer engineering Professor Sanjay Banerjee, a co-author of the Science paper, directs both SWAN and the DARPA Center.
"By having a materials scientist of Colombo's caliber with such extensive knowledge about all aspects of semiconductor processing and now co-developing the materials science of graphene with us, I think our team exemplifies what collaboration between industrial scientists and engineers with university personnel can be," said Ruoff, who holds the Cockrell Family Regents Chair #7. "This industry-university collaboration supports both the understanding of the fundamental science as well its application."
Other co-authors of the work not previously mentioned include: research associate Richard Piner of the Department of Mechanical Engineering; Assistant Professor Emanuel Tutuc of the Department of Electrical and Computer Engineering; post-doctoral fellows Jinho An, Weiwei Cai, Inhwa Jung, Aruna Velamakanni and Dongxing Yang in the Department of Mechanical Engineering; and graduate students Seyoung Kim and Junghyo Nah in the Department of Electrical and Computer Engineering.
Journal reference:
. Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils. Science, May 8, 2009
Adapted from materials provided by University of Texas at Austin, via EurekAlert!, a service of AAAS.

Low Cost, Dexterous Robotic Hand Operated By Compressed Air

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ScienceDaily (May 7, 2009) — The Robotics and Mechanisms Laboratory (RoMeLa) of the College of Engineering at Virginia Tech has developed a unique robotic hand that can firmly hold objects as heavy as a can of food or as delicate as a raw egg, while dexterous enough to gesture for sign language.

Named RAPHaEL (Robotic Air Powered Hand with Elastic Ligaments), the fully articulated robotic hand is powered by a compressor air tank at 60 psi and a novel accordion type tube actuator. Microcontroller commands operate the movement to coordinate the motion of the fingers.
“This air-powered design is what makes the hand unique, as it does not require the use of any motors or other actuators, the grasping force and compliance can be easily adjusted by simply changing the air pressure,” said Dennis Hong, RoMeLa director and the faculty adviser on the project. RoMeLa is part of Virginia Tech’s department of mechanical engineering (ME).
The grip derives from the extent of pressure of the air. A low pressure is used for a lighter grip, while a higher pressure allows for a sturdier grip. The compliance of compressed air also aids in the grasping as the fingers can naturally follow the contour of the grasped object.
“There would be great market potential for this hand, such as for robotic prosthetics, due to the previously described benefits, as well as low cost, safety and simplicity,” Hong said. The concept has won RoMeLa first place in the recent 2008-2009 Compressed Air and Gas Institute (CAGI)’s Innovation Award Contest, with team members sharing $2,500 and the College of Engineering receiving a separate $8,000 monetary award.
The $10,500 prize was announced in April by the Cleveland, Ohio-based CAGI, an industry organization. The design competition was an invitation-only program, with projects overviews – including written reports and video – being sent to the judging panel. Teams from Virginia Tech, the Milwaukee School of Engineering and Buffalo State College each submitted entries on their air-powered designs for judging. Six teams in all participated, according to Hong.
It is the second year in a row that RoMeLa has won first place in the CAGI competition. A judge on the panel said of the robotic hand, “It is a cutting edge concept, and the engineering was no less than brilliant.”
Student team members, all ME majors, are:
Colin Smith of Reston, Va., a senior
Kyle Cothern of Fredericksburg, Va., a junior.
Carlos Guevara of El Salvador, a senior.
Alexander McCraw of York, Pa., a senior.
RAPHaEL is just part of a larger RoMeLa project: The humanoid robot known as CHARLI (Cognitive Humanoid Robot with Learning Intelligence). The hand already is on its second prototype design, with the newer model to be used by CHARLI. Once the newer model hand is connected to the larger body, it will be able to pick up – not just grasp and hold – objects as would a person.
Hong has said CHARLI is the first full-sized bipedal walking humanoid robot to be built entirely in the United States. The 5-foot tall robot will be used as a general humanoid research platform as well as for the RoboCup Humanoid Teen size league for RoboCup 2010.
The larger CHARLI project is partially sponsored by the Virginia Tech Student Engineering Council and by the National Science Foundation (NSF). Hong said he hopes to have CHARLI one day walking about around campus and completing tours of Virginia Tech for visitors and potential students.
Adapted from materials provided by Virginia Tech, via Newswise.

Method To Integrate Plasmon-based Nanophotonic Circuitry With State-of-the-art ICs Developed

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ScienceDaily (May 7, 2009) — IMEC, an independent nanoelectronics research institute, reports a method to integrate high-speed CMOS electronics and nanophotonic circuitry based on plasmonic effects. Metal-based nanophotonics (plasmonics) can squeeze light into nanoscale structures that are much smaller than conventional optic components. Plasmonic technology, today still in an experimental stage, has the potential to be used in future applications such as nanoscale optical interconnects for high performance computer chips, extremely sensitive (bio)molecular sensors, and highly efficient thin-film solar cells.

The optical properties of nanostructured (noble) metals show great promise for use in nanophotonic applications. When such nanostructures are illuminated with visible to near-infrared light, the excitation of collective oscillations of conduction electrons – called surface plasmons – generates strong optical resonances. Moreover, surface plasmons are capable of capturing, guiding, and focusing electromagnetic energy in deep-subwavelength length-scales, i.e. smaller than the diffraction limit of the light. This is unlike conventional dielectric optical waveguides, which are limited by the wavelength of the light, and which therefore cannot be scaled down to tens of nanometers, which is the dimension of the components on today’s nanoelectronic ICs.
Nanoscale plasmonic circuits would allow massive parallel routing of optical information on ICs. But eventually that high-bandwidth optical information has to be converted to electrical signals. To make such ICs that combine high-speed CMOS electronics and plasmonic circuitry, efficient and fast interfacing components are needed that couple the signals from plasmon waveguides to electrical devices.
As an important stepping stone to such components, IMEC has now demonstrated integrated electrical detection of highly confined short-wavelength surface plasmon polaritons in metal-dielectric-metal plasmon waveguides. The detection was done by embedding a photodetector in a metal plasmon waveguide. Because the waveguide and the photodetector have the same nanoscale dimensions, there is an efficient coupling of the surface plasmons into the photodetector and an ultrafast response.
IMEC has set up a number of experiments that unambiguously demonstrate this electrical detection. The strong measured polarization dependence, the experimentally obtained influence of the waveguide length and the measured spectral response are all in line with theoretical expectations, obtained from finite element and finite-difference-time-domain calculations. These results pave the way for the integration of nanoscale plasmonic circuitry and high-speed electronics.
IMEC’s results are published in the May issue of Nature Photonics.
Adapted from materials provided by Interuniversity Microelectronics Centre (IMEC).

Self-cleaning Objects And Water-striding Robots May Be Possible With Super Hydrophobic Materials

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ScienceDaily (May 5, 2009) — Self-cleaning walls, counter tops, fabrics, even micro-robots that can walk on water -- all those things and more could be closer to reality because of research recently completed by scientists at the University of Nebraska-Lincoln and at Japan's RIKEN institute.

Humans have marveled for millennia at how water beads up and rolls off flowers, caterpillars and some insects, and how insects like water striders are able to walk effortlessly on water. It's a property called super hydrophobia and it's been examined seriously by scientists since at least the 1930s.
"A lot of people study this and engineers especially like the water strider because it can walk on water," said Xiao Cheng Zeng, Ameritas university professor of chemistry at UNL. "Their legs are super hydrophobic and each leg can hold about 15 times their weight. 'Hydrophobic' means water really doesn't like their legs and that's what keeps them on top. A lot of scientists and engineers want to develop surfaces that mimic this from nature."
In a paper to be published in the May 4-8 online edition of the Proceedings of the National Academy of Sciences, Zeng and his Japanese colleagues, Takahiro Koishi of the University of Fukui and RIKEN, Kenji Yasuoka of Keio University, and Shigenori Fujikawa and Toshikazu Ebisuzaki of RIKEN, give engineers and materials scientists important clues in how to develop the long-sought super hydrophobic materials.
In nature, organisms like caterpillars, water striders and the lotus achieve super hydrophobia through a two-level structure -- a hydrophobic waxy surface made super hydrophobic by the addition of microscopic hair-like structures that may be covered by even smaller hairs, greatly increasing the surface area of the organism and making it impossible for water droplets to stick.
Using the superfast supercomputer at RIKEN (the fastest in the world when the research started in 2005), the team designed a computer simulation to perform tens of thousands of experiments that studied how surfaces behaved under many different conditions. Zeng and his colleagues used the RIKEN computer to "rain" virtual water droplets of different sizes and at different speeds on surfaces that had pillars of various heights and widths, and with different amounts of space between the pillars.
They learned there is a critical pillar height, depending on the particular structure of the pillars and their chemical properties, beyond which water droplets cannot penetrate. If the droplet can penetrate the pillar structure and reach the waxy surface, it is in the merely hydrophobic Wenzel state (named for Robert Wenzel, who found the phenomenon in nature in 1936). If it the droplet cannot penetrate the pillars to touch the surface, the structure is in the super hydrophobic Cassie state (named for A.B.D. Cassie, who discovered it in 1942), and the droplet rolls away.
"This kind of simulation -- we call it 'computer-aided surface design' -- can really help engineers in designing a better nanostructured surface," Zeng said. "In the Cassie state, the water droplet stays on top and it can carry dirt away. In the Wenzel state, it's sort of stuck on the surface and lacks self-cleaning functionality. When you build a nanomachine -- a nanorobot -- in the future, you will want to build it so it can self-clean."
Zeng said there were three main advantages to performing the experiments on a computer rather that in a laboratory. First, they were able to conduct thousands more repetitions than would have been possible in a lab. Second, they didn't have to worry about variables such as dirt, temperature and air flow. Third, they could control the size of droplets down to the exact number of molecules, whereas in a laboratory experiment the droplets would unavoidably vary by tens of thousands of molecules.
The idea for the experiment came about in 2005 when Zeng visited RIKEN during his year as a fellow of the John Simon Guggenheim Foundation, which paid for the start-up for the project. Koishi spent the spring of 2005 with Zeng at UNL as they designed the project in detail. Yasuoka and his family spent the 2006-07 academic year in Lincoln during his a one-year sabbatical with Zeng, in part because of this project.
"We wanted to design a grand-challenge project so we could take advantage of the RIKEN super computer," Zeng said. "We thought this was an interesting project and we need a very, very fast computer to deal with it. I also have to acknowledge the Nebraska Research Initiative, the Department of Energy and the National Science Foundation. The NRI is great because it allows me to do highly risky research, to develop this kind of challenging project."
Adapted from materials provided by University of Nebraska-Lincoln, via EurekAlert!, a service of AAAS.

Mini Helicopters As Disaster Helpers

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ScienceDaily (May 6, 2009) — The collapse of the Cologne city archive building triggered a race against time for the rescue workers. After such disasters, detailed information is needed in order to select the appropriate course of action. For example, it is necessary to know if and where people are trapped and if adjacent buildings are in danger of collapse. An unmanned mini helicopter can handle this dangerous reconnaissance work for the emergency services.

The “quadrocopter” has a diameter of one meter and, thanks to its maneuverability, can negotiate collapsed buildings. At present the flying disaster helper operates solo, but it could soon be joined by reinforcements: Fraunhofer research scientists are working on their deployment in swarms. Currently this would only be possible with considerable manpower effort – the helicopters cannot communicate with each other and each one would have to be individually controlled.
To ensure that, in future, one person can control all the helicopters deployed, the scientists at the Fraunhofer Institute for Information and Data Processing IITB in Karlsruhe have developed a software which functions as a director of operations. “Our program enables the quadrocopters to coordinate their activities themselves,” explains Dr. Axel Bürkle, project manager at the IITB. “One of them can fly up close to victims to investigate their injuries while another reconnoiters the fastest route for getting them out.”
The program consists of individual modules, the software agents, which can be programmed with a repertoire of tasks. One software agent is assigned to each quadrocopter. The miniature flying machines are equipped with various sensors such as cameras, infrared cameras, laser measurement equipment and sniffer devices for identifying hazardous substances. They can also radio images, videos and other data to the ground station, where the software agents assess the information and, via an interface, send instructions for action to the quadrocopters.
The special factor is that the software agents are able to network with each other independently and exchange information. This means that they can harmonize their commands to the quadrocopters. What's more, software agents are able to learn. They memorize what happened in particular situations and respond more quickly the next time. The development engineers are currently examining the use of the system in simulations of various scenarios. They have further applications in mind, such as monitoring of premises. The first quadrocopter swarms could be ready for service in about a year.
Adapted from materials provided by Fraunhofer-Gesellschaft.

Underwater Robot With A Sense Of Touch

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ScienceDaily (May 6, 2009) — The robot dives into the sea, swims to the submerged cable and carries out the necessary repairs, but the person controlling the robot does not have an easy task. It is pitch dark and the robot’s lamp does not help much. What’s more, the current keeps pulling the robot away from where it needs to carry out the work.

In future, the robot could find its own way. A sensor will endow it with a sense of touch and help it to detect its undersea environment autonomously.
“One component in this tactile capability is a strain gauge,” says Marcus Maiwald, project manager at the Fraunhofer Institute for Manufacturing Technology and Applied Materials Research IFAM in Bremen. Together with his Fraunhofer colleagues and staff at the German Research Center for Artificial Intelligence DFKI, Bremen Laboratory, he has developed the model of an underwater robot with a sense of touch.
“If the robot encounters an obstacle," he explains, "the strain gauge is distorted and the electrical resistance changes. The special feature of our strain gauge is that it is not glued but printed on – which means we can apply the sensor to curved surfaces of the robot.”
The single printed strip is just a few ten micrometers wide, i.e. about half the width of a human hair. As a result, the strain gauges can be applied close to each other and the robot can identify precisely where it is touching an obstacle. The sensor is protected from the salt water by encapsulation.
To produce the strain gauges, the research scientists atomize a solution with nanoparticles to create an aerosol. A software system guides the aerosol stream to the right position. Focusing gas shrouds the beam and ensures that it does not fan out.
At the Sensor and Test trade show from May 26 to 28 in Nuremberg, the research scientists are presenting an octopus-shaped underwater robot which is fitted with a printed sensor.
Adapted from materials provided by Fraunhofer-Gesellschaft, via AlphaGalileo.

Electronic Books: Make Brighter, Full-color Electronic Readers

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ScienceDaily (May 6, 2009) — Thinking about getting an e-reader but not sure if you like reading the dim screen? For the first time “e-paper” will achieve the brilliance of printed media, as described in the May issue of Nature Photonics.

An international collaboration of the University of Cincinnati, Sun Chemical, Polymer Vision and Gamma Dynamics has announced Electrofluidic Display Technology (EFD), the first technology to electrically switch the appearance of pigments in a manner that provides visual brilliance equal to conventional printed media.
This new entry into the race for full-color electronic paper can potentially provide better than 85 percent “white-state reflectance,” a performance level required for consumers to accept reflective display applications such as e-books, cell-phones and signage.
“If you compare this technology to what’s been developed previously, there’s no comparison,” says developer Jason Heikenfeld, assistant professor of electrical engineering in UC’s College of Engineering. “We’re ahead by a wide margin in critical categories such as brightness, color saturation and video speed.”
This work, which has been underway for several years, has just been published in the paper “
Electrofluidic displays using Young–Laplace transposition of brilliant pigment dispersions.
Lead author Heikenfeld explains the primary advantage of the approach. “The ultimate reflective display would simply place the best colorants used by the printing industry directly beneath the front viewing substrate of a display,” he says. “In our EFD pixels, we are able to hide or reveal colored pigment in a manner that is optically superior to the techniques used in electrowetting, electrophoretic and electrochromic displays.”
Because the optically active layer can be less than 15 microns thick, project partners at PolymerVision see strong potential for rollable displays. The product offerings could be extremely diverse, including electronic windows and tunable color casings on portable electronics.
Furthermore, because three project partners are located in Cincinnati (UC, Sun Chemical, Gamma Dynamics), technology commercialization could lead to creation of numerous high-tech jobs in southwest Ohio.
To expedite commercialization, a new company has been launched: Gamma Dynamics with founding members of this company being John Rudolph as president (formerly of Corning), a world-recognized scientist as CTO (who cannot be announced until July), and Heikenfeld as principal scientist.
“This takes the Amazon Kindle, for example, which is black and white, and could make it full color,” Heikenfeld says. “So now you could take it from a niche product to a mainstream product.”
Funding for this work was provided by Sun Chemical, PolymerVision, the National Science Foundation and the Air Force Research Laboratory.
Adapted from materials provided by University of Cincinnati.