Thursday, December 20, 2007

Move Over, Silicon: Advances Pave Way For Powerful Carbon-based Electronics


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ScienceDaily (Dec. 20, 2007) — Bypassing decades-old conventions in making computer chips, Princeton engineers developed a novel way to replace silicon with carbon on large surfaces, clearing the way for new generations of faster, more powerful cell phones, computers and other electronics.
The electronics industry has pushed the capabilities of silicon -- the material at the heart of all computer chips -- to its limit, and one intriguing replacement has been carbon, said Stephen Chou, professor of electrical engineering. A material called graphene -- a single layer of carbon atoms arranged in a honeycomb lattice -- could allow electronics to process information and produce radio transmissions 10 times better than silicon-based devices.
Until now, however, switching from silicon to carbon has not been possible because technologists believed they needed graphene material in the same form as the silicon used to make chips: a single crystal of material eight or 12-inches wide. The largest single-crystal graphene sheets made to date have been no wider than a couple millimeters, not big enough for a single chip. Chou and researchers in his lab realized that a big graphene wafer is not necessary, as long they could place small crystals of graphene only in the active areas of the chip. They developed a novel method to achieve this goal and demonstrated it by making high-performance working graphene transistors.
"Our approach is to completely abandon the classical methods that industry has been using for silicon integrated circuits," Chou said.
Chou, along with graduate student Xiaogan Liang and materials engineer Zengli Fu, published their findings in the December 2007 issue of Nano Letters, a leading journal in the field. The research was funded in part by the Office of Naval Research.
In their new method, the researchers make a special stamp consisting of an array of tiny flat-topped pillars, each one-tenth of a millimeter wide. They press the pillars against a block of graphite (pure carbon), cutting thin carbon sheets, which stick to the pillars. The stamp is then removed, peeling away a few atomic layers of graphene. Finally, the stamp is aligned with and pressed against a larger wafer, leaving the patches of graphene precisely where transistors will be built.
The technique is like printing, Chou said. By repeating the process and using variously shaped stamps (the researchers also made strips instead of round pillars), all the active areas for transistors are covered with single crystals of graphene.
"Previously, scientists have been able to peel graphene sheets from graphite blocks, but they had no control over the size and location of the pieces when placing them on a surface," Chou said.
One innovation that made the technique possible was to coat the stamp with a special material that sticks to carbon when it is cold and releases when it is warm, allowing the same stamp to pick up and release the graphene.
Chou's lab took the next step and built transistors -- tiny on-off switches -- on their printed graphene crystals. Their transistors displayed high performance; they were more than 10 times faster than silicon transistors in moving "electronic holes" -- a key measure of speed.
The new technology could find almost immediate use in radio electronics, such as cell phones and other wireless devices that require high power output, Chou said. Depending on the level of interest from industry, the technique could be applied to wireless communication devices within a few years, Chou predicted.
"What we have done is shown that this approach is possible; the next step is to scale it up," Chou said.
Adapted from materials provided by Princeton University, Engineering School.

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Wednesday, December 19, 2007

2-D Invisibility Cloak For Visible Light Created


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ScienceDaily (Dec. 19, 2007) — Harry Potter may not have talked much about plasmonics in J. K. Rowling's fantasy series, but University of Maryland researchers are using this emerging technology to develop an invisibility cloak that exists beyond the world of bespectacled teenage wizards.
A research team at Maryland's A. James Clark School of Engineering comprised of Professor Christopher Davis, Research Scientist Igor Smolyaninov, and graduate student Yu-Ju Hung, has used plasmon technology to create the world's first invisibility cloak for visible light. The engineers have applied the same technology to build a revolutionary superlens microscope that allows scientists to see details of previously undetectable nanoscale objects.
Generally speaking, when we see an object, we see the visible light that strikes the object and is reflected. The Clark School team's invisibility cloak refracts (or bends) the light that strikes it, so that the light moves around and past the cloak, reflecting nothing, leaving the cloak and its contents "invisible."
The invisibility cloak device is a two-dimensional pattern of concentric rings created in a thin, transparent acrylic plastic layer on a gold film. The plastic and gold each have different refractive properties. The structured plastic on gold in different areas of the cloak creates "negative refraction" effects, which bend plasmons—electron waves generated when light strikes a metallic surface under precise circumstances—around the cloaked region.
This manipulation causes the plasmon waves to appear to have moved in a straight line. In reality they have been guided around the cloak much as water in a stream flows around a rock, and released on the other side, concealing the cloak and the object inside from visible light. The invisibility that this phenomenon creates is not absolutely perfect because of energy loss in the gold film.
The team achieved this invisibility under very specialized conditions. The researchers' cloak is just 10 micrometers in diameter; by comparison, a human hair is between 50 to 100 micrometers wide. Also, the cloak uses a limited range of the visible spectrum, in two dimensions. It would be a significant challenge to extend the cloak to three dimensions because researchers would need to control light waves both magnetically and electronically to steer them around the hidden object. The technology initially may work only for small objects of specific controlled shape.
The team also has used plasmonics to develop superlens microscopy technology, which can be integrated into a conventional optical microscope to view nanoscale details of objects that were previously undetectable.
The superlens microscope could one day image living cells, viruses, proteins, DNA molecules, and other samples, operating much like a point-and-shoot camera. This new technology could revolutionize the capability to view nanoscale objects at a crucial stage of their development. The team believes they can improve the resolution of their microscope images down to about 10 nanometers—one ten thousandth of the width of a human hair.
A large reason for the success of the group's innovations in both invisibility and microscopy is that surface plasmons have very short wave lengths, and can therefore move data around using much smaller-scale guiding structures than in existing devices. These small, rapid waves are generated at optical frequencies, and can transport large amounts of data. The group also has made use of the unique properties of metamaterials, artificially structured composites that help control electromagnetic waves in unusual ways using plasmonic phenomena.
The diverse applications the group has derived from their plasmonics research is an example of the ingenuity of researchers approaching new and dynamic technologies that offer broad and unprecedented capabilities. The research has attracted a great deal of attention within the scientific community, industry and government agencies. Related plasmonics research offers applications for military and computer chip technologies, which could benefit from the higher frequencies and rapid data transfer rates that plasmons offer.
The team's research has been funded by the National Science Foundation and Clark School Corporate Partner BAE Systems.
Smolyaninov and Davis have published an article in the journal Science about their superlens microscope technology, titled "Magnifying Superlens in the Visible Frequency Range." The group and their colleagues from Purdue University will also soon publish a paper about their invisibility cloak research.
Adapted from materials provided by University of Maryland.

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New Nanowire Battery Holds 10 Times The Charge Of Existing Ones


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ScienceDaily (Dec. 20, 2007) — Stanford researchers have found a way to use silicon nanowires to reinvent the rechargeable lithium-ion batteries that power laptops, iPods, video cameras, cell phones, and countless other devices.
The new version, developed through research led by Yi Cui, assistant professor of materials science and engineering, produces 10 times the amount of electricity of existing lithium-ion, known as Li-ion, batteries. A laptop that now runs on battery for two hours could operate for 20 hours, a boon to ocean-hopping business travelers.
"It's not a small improvement," Cui said. "It's a revolutionary development."
The greatly expanded storage capacity could make Li-ion batteries attractive to electric car manufacturers. Cui suggested that they could also be used in homes or offices to store electricity generated by rooftop solar panels.
"Given the mature infrastructure behind silicon, this new technology can be pushed to real life quickly," Cui said.
The electrical storage capacity of a Li-ion battery is limited by how much lithium can be held in the battery's anode, which is typically made of carbon. Silicon has a much higher capacity than carbon, but also has a drawback.
Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use (i.e., when playing your iPod) as the lithium is drawn out of the silicon. This expand/shrink cycle typically causes the silicon (often in the form of particles or a thin film) to pulverize, degrading the performance of the battery.
Cui's battery gets around this problem with nanotechnology. The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture.
Research on silicon in batteries began three decades ago. Candace Chan, a graduate student of Cui, explained: "The people kind of gave up on it because the capacity wasn't high enough and the cycle life wasn't good enough. And it was just because of the shape they were using. It was just too big, and they couldn't undergo the volume changes."
Then, along came silicon nanowires. "We just kind of put them together," Chan said.
For their experiments, Chan grew the nanowires on a stainless steel substrate, providing an excellent electrical connection. "It was a fantastic moment when Candace told me it was working," Cui said.
Cui said that a patent application has been filed. He is considering formation of a company or an agreement with a battery manufacturer. Manufacturing the nanowire batteries would require "one or two different steps, but the process can certainly be scaled up," he added. "It's a well understood process."
The breakthrough is described in detail in a paper, "High-performance lithium battery anodes using silicon nanowires," published online Dec. 16 in Nature Nanotechnology, written by Cui, his graduate chemistry student Candace Chan and five others.
Also contributing to the paper in Nature Nanotechnology were Halin Peng and Robert A. Huggins of Materials Science and Engineering at Stanford, Gao Liu of Lawrence Berkeley National Laboratory, and Kevin McIlwrath and Xiao Feng Zhang of the electron microscope division of Hitachi High Technologies in Pleasanton, Calif.
Adapted from materials provided by Stanford University.

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Sunday, December 16, 2007

Biometrics: Unlocking Doors With Your Eyes


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ScienceDaily (Dec. 14, 2007) — It is not science fiction to think that our eyes could very soon be the key to unlocking our homes, accessing our bank accounts and logging on to our computers, according to Queensland University of Technology researcher Sammy Phang.
Research by Ms Phang, from QUT's Faculty of Built Environment and Engineering, is helping to remove one of the final obstacles to the everyday application of iris scanning technology.
Ms Phang said the pattern of an iris was like a fingerprint in that every iris was unique. "Every individual iris is unique and even the iris pattern of the left eye is different from the right. The iris pattern is fixed throughout a person's lifetime" she said.
"By using iris recognition it is possible to confirm the identity of a person based on who the person is rather than what the person possesses, such as an ID card or password.
"It is already being used around the world and it is possible that within the next 10 to 20 years it will be part of our everyday lives."
Ms Phang said although iris recognition systems were being used in a number of civilian applications, the system was not perfect. "Changes in lighting conditions change a person's pupil size and distort the iris pattern," she said.
"If the pupil size is very different, the distortion of the iris pattern can be significant, and makes it hard for the iris recognition system to work properly."
To overcome this flaw, Ms Phang has developed the technology to estimate the effect of the change in the iris pattern as a result of changes in surrounding lighting conditions. "It is possible for a pupil to change in size from 0.8mm to 8mm, depending on lighting conditions," she said.
Ms Phang said by using a high-speed camera which could capture up to 1200 images per second it was possible to track the iris surface's movements to study how the iris pattern changed depending on the variation of pupil sizes caused by the light. "The study showed that everyone's iris surface movement is different."
She said results of tests conducted using iris images showed it was possible to estimate the change on the surface of the iris and account for the way the iris features changed due to different lighting conditions.
"Preliminary image similarity comparisons between the actual iris image and the estimated iris image based on this study suggest that this can possibly improve iris verification performance."
Adapted from materials provided by Queensland University of Technology.

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Sunday, December 2, 2007

Cynthia Breazeal


Cynthia Breazeal directs the Lab's Personal Robots group and holds the LG Career Development chair, having previously been a postdoctoral associate at MIT's Artificial Intelligence (AI) Lab. Breazeal is particularly interested in developing creature-like technologies that exhibit social commonsense and engage people in familiar human terms. Kismet, her anthropomorphic robotic head, has been featured in international media and is the subject of her book Designing Sociable Robots, published by the MIT Press. She continues to develop anthropomorphic robots as part of her ongoing work of building artificial systems that learn from and interact with people in an intelligent, life-like, and sociable manner. Breazeal earned ScD and MS degrees at MIT in electrical engineering and computer science, and a BS in electrical and computer engineering from the University of California, Santa Barbara.





Cyberflora:




Cynthia Breazeal
Associate Professor of Media Arts and Sciences
LG Career Development Professor of Media Arts and Sciences
Group: Personal Robots
Office: E15-449
Phone: (617) 252-5601
Fax: (617) 225-2009
E-mail: cynthiab@media
addresses are formatted username@media.mit.edu
URL: http://web.media.mit.edu/~cynthiab/

Intelligent Software Helps Build Perfect Robotic Hand


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ScienceDaily (Dec. 2, 2007) — Scientists in Portsmouth and Shanghai are working on intelligent software that will take them a step closer to building the perfect robotic hand.
Using artificial intelligence, they are creating software which will learn and copy human hand movements.
They hope to replicate this in a robotic device which will be able to perform the dexterous actions only capable today by the human hand.
Dr Honghai Liu, senior lecturer at the University of Portsmouth’s Institute of Industrial Research, and Professor Xiangyang Zhu from the Robotics Institute at Jiao Tong University in Shanghai, were awarded a Royal Society grant to further their research.
The technology has the potential to revolutionise the manufacturing industry and medicine and scientists hope that in the future it could be used to produce the perfect artificial limb.
“A robotic hand which can perform tasks with the dexterity of a human hand is one of the holy grails of science,” said Dr Honghai Liu, who lectures artificial intelligence at the University’s Institute of Industrial Research. The Institute specialises in artificial intelligence including intelligent robotics, image processing and intelligent data analysis.
He said: “We are talking about having super high level control of a robotic device.
Nothing which exists today even comes close.”
Dr Liu used a cyberglove covered in tiny sensors to capture data about how the human hand moves. It was filmed in a motion capture suite by eight high-resolution CCD cameras with infrared illumination and measurement accuracy up to a few millimetres.
Professor Xiangyang Zhu from The Robotics Institute at the Jiao Tong University in Shanghai, which is recognised as one of the world-class research institutions on robotics, said that the research partnership would strengthen the interface between artificial intelligence techniques and robotics and pave the way for a new chapter in robotics technology.
“Humans move efficiently and effectively in a continuous flowing motion, something we have perfected over generations of evolution and which we all learn to do as babies. Developments in science mean we will teach robots to move in the same way.”
Adapted from materials provided by University Of Portsmouth.

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