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

Source:

http://www.sciencedaily.com/releases/2007/12/071218192013.htm

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.

Fausto Intilla

www.oloscience.com

2-D Invisibility Cloak For Visible Light Created

Source:

http://www.sciencedaily.com/releases/2007/12/071218192009.htm

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.

Fausto Intilla

www.oloscience.com

New Nanowire Battery Holds 10 Times The Charge Of Existing Ones

Source:

http://www.sciencedaily.com/releases/2007/12/071219103105.htm

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.

Fausto Intilla

www.oloscience.com

Biometrics: Unlocking Doors With Your Eyes

Source:

http://www.sciencedaily.com/releases/2007/12/071204100422.htm

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.

Fausto Intilla

www.oloscience.com

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

Source:

http://www.sciencedaily.com/releases/2007/11/071130231044.htm

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.

Fausto Intilla

www.oloscience.com

Engineers Give Industry A Moth's Eye View

Source:

http://www.sciencedaily.com/releases/2007/11/071126115318.htm

ScienceDaily (Nov. 28, 2007) — When moths fly at night, their eyes need to capture all the light available. To do this, certain species have evolved nanoscopic structures on the surface of their eyes which allow almost no light to reflect off the surface and hence to escape.

Now scientists at MicroBridge, a project at Cardiff University's Manufacturing Engineering Centre (MEC), have adopted the model to create an industrial lens for use in a low light environment.
The structures on the surface of the new lens are less than 100 nanometres in height (a nanometre is one millionth of a millimetre). They need to be smaller than the wavelength of light to avoid disrupting the light as it enters the lens.
The tiny features of the lens mould were created using the MEC's Focused Ion Beam. The beam uses highly charged atomic particles to machine materials in microscopic detail.
Dr Robert Hoyle of the MEC said: "This was a particularly complicated challenge. Not only did the lenses have to be of very precise curvature but the nanoscopic structures on the lens surfaces had to be smaller than the wavelength of light so as to smooth out the sharp refractive index change as the light strikes the surface of the lens. This smoothing of the refractive index reduces the reflectiveness of the lens thus allowing it to capture more light. The end result has a number of highly practical uses for industry."
The research team is now looking at using the lens in optoelectronics and photovoltaic applications in semiconductors, including solar cells, where loss of light is a major problem. The lens also has potential uses in fibre optics, sensors and medical diagnostic devices.
Adapted from materials provided by Cardiff University.

Fausto Intilla

www.oloscience.com

High Performance Field-effect Transistors With Thin Films Of Carbon 60 Produced

Source:

http://www.sciencedaily.com/releases/2007/11/071126121735.htm

ScienceDaily (Nov. 27, 2007) — Using room-temperature processing, researchers at the Georgia Institute of Technology have fabricated high-performance field effect transistors with thin films of Carbon 60, also known as fullerene. The ability to produce devices with such performance with an organic semiconductor represents another milestone toward practical applications for large area, low-cost electronic circuits on flexible organic substrates.

The new devices -- which have electron-mobility values higher than amorphous silicon, low threshold voltages, large on-off ratios and high operational stability -- could encourage more designers to begin working on such circuitry for displays, active electronic billboards, RFID tags and other applications that use flexible substrates.
"If you open a textbook and look at what a thin-film transistor should do, we are pretty close now," said Bernard Kippelen, a professor in Georgia Tech's School of Electrical and Computer Engineering and the Center for Organic Photonics and Electronics. "Now that we have shown very nice single transistors, we want to demonstrate functional devices that are combinations of multiple components. We have everything ready to do that."
Fabrication of the C60 transistors was reported August 27th in the journal Applied Physics Letters. The research was supported by the U.S. National Science Foundation through the STC program MDITR, and the U.S. Office of Naval Research.
Researchers have been interested in making field-effect transistors and other devices from organic semiconductors that can be processed onto various substrates, including flexible plastic materials. As an organic semiconductor material, C60 is attractive because it can provide high electron mobility -- a measure of how fast current can flow. Previous reports have shown that C60 can yield mobility values as high as six square centimeters per volt-second (6 cm2/V/s). However, that record was achieved using a hot-wall epitaxy process requiring processing temperatures of 250 degrees Celsius -- too hot for most flexible plastic substrates.
Though the transistors produced by Kippelen's research team display slightly lower electron mobility -- 2.7 to 5 cm2/V/s -- they can be produced at room temperature.
"If you want to deposit transistors on a plastic substrate, you really can't have any process at a temperature of more than 150 degrees Celsius," Kippelen said. "With room temperature deposition, you can be compatible with many different substrates. For low-cost, large area electronics, that is an essential component."
Because they are sensitive to contact with oxygen, the C60 transistors must operate under a nitrogen atmosphere. Kippelen expects to address that limitation by using other fullerene molecules -- and properly packaging the devices.
The new transistors were fabricated on silicon for convenience. While Kippelen isn't underestimating the potential difficulty of moving to an organic substrate, he says that challenge can be overcome.
Though their performance is impressive, the C60 transistors won't threaten conventional CMOS chips based on silicon. That's because the applications Kippelen has in mind don't require high performance.
"There are a lot of applications where you don't necessarily need millions of fast transistors," he said. "The performance we need is by far much lower than what you can get in a CMOS chip. But whereas CMOS is extremely powerful and can be relatively low in cost because you can make a lot of circuits on a wafer, for large area applications CMOS is not economical."
A different set of goals drives electronic components for use with low-cost organic displays, active billboards and similar applications.
"If you look at a video display, which has a refresh rate of 60 Hz, than means you have to refresh the screen every 16 milliseconds," he noted. "That is a fairly low speed compared to a Pentium processor in your computer. There is no point in trying to use organic materials for high-speed processing because silicon is already very advanced and has much higher carrier mobility."
Now that they have demonstrated attractive field-effect C60 transistors, Kippelen and collaborators Xiao-Hong Zhang and Benoit Domercq plan to produce other electronic components such as inverters, ring oscillators, logic gates, and drivers for active matrix displays and imaging devices. Assembling these more complex systems will showcase the advantages of the C60 devices.
"The goal is to increase the complexity of the circuits to see how that high mobility can be used to make more complex structures with unprecedented performance," Kippelen said.
The researchers fabricated the transistors by depositing C60 molecules from the vapor phase into a thin film atop a silicon substrate onto which a gate electrode and gate dielectric had already been fabricated. The source and drain electrodes were then deposited on top of the C60 films through a shadow mask.
Kippelen's team has been working with C60 for nearly ten years, and is also using the material in photovoltaic cells. Beyond the technical advance, Kippelen believes this new work demonstrates the growing maturity of organic electronics.
"This progress may trigger interest among more conventional electronic engineers," he said. "Most engineers would like to work with the latest technology platform, but they would like to see a level of performance showing they could actually implement these circuits. If you can demonstrate -- as we have -- that you can get transistors with good reproducibility, good stability, near-zero threshold voltages, large on-off current ratios and performance levels higher than amorphous silicon, that may convince designers to consider this technology."
Adapted from materials provided by Georgia Institute of Technology.

Fausto Intilla

www.oloscience.com

Powerful Microscope May Help Cancer Research

Source:

http://www.sciencedaily.com/releases/2007/11/071126100608.htm

ScienceDaily (Nov. 27, 2007) — The Centenary Institute unveiled a powerful microscope unlike any other in Australia. Representing the cutting edge in medical technology and microscopy, the unique imaging features of the multiphoton microscope will enable scientists at the Centenary Institute unprecedented access to the secret workings of living tissues at the cellular and molecular level.

The Centenary Institute is equally excited about the arrival of Austrian Professor Wolfgang Weninger, one of only a handful of people in the world who specialises in using the multiphoton microscope in the immunology field to view immune responses in real-time in living tissue.
At the Centenary, Professor Weninger will lead a team of researchers to study the dynamics of the immune system's response to cancer and infectious diseases.
Professor Weninger said, "Cancer is still a leading cause of death in Australia. There is a need to develop improved anti-cancer therapies based on the use of the body's own resources - namely our immune system. This type of microscope is an outstanding tool to study how our bodies fight cancer both in early and advanced stages. If we can learn more about how our immune system attacks cancer cells directly in the context of intact tissues, we hope to develop improved immuno-therapies."
Using the multiphoton microscope, Professor Weninger's team pioneered ground-breaking imaging models to record how the body's defences fight tumours and infectious diseases. He has made real-time videos of white blood cells invading and destroying cancer cells in living tissue.
I am confident that the results of his team's research will vastly improve our understanding of how the body's immune system fights cancer and infectious diseases. The multiphoton microscope will also support the research of other Centenary scientists particularly in autoimmune and liver diseases."
The multiphoton microscope at the Centenary Institute has two unique features, its imaging mode and laser. The unique imaging mode uses multiple laser beams and means fast moving objects and dynamic processes in living tissue can be viewed, for example, cells in the blood stream. The laser has been enhanced with a unit called an OPO that produces longer wavelengths of light than those used in other microscopes enabling researchers to potentially look deeper into living tissue than ever before.
Adapted from materials provided by Centenary Institute.

Fausto Intilla

www.oloscience.com

New T-ray Source Could Improve Airport Security, Cancer Detection

Source:

http://www.sciencedaily.com/releases/2007/11/071126121732.htm

ScienceDaily (Nov. 27, 2007) — Going through airport security can be such a hassle. Shoes, laptops, toothpastes, watches and belts all get taken off, taken out, scanned, examined, handled and repacked. But "T-rays", a completely safe form of electromagnetic radiation, may reshape not only airport screening procedures but also medical imaging practices.

Scientists at the U.S. Department of Energy's Argonne National Laboratory, along with collaborators in Turkey and Japan, have created a compact device that could lead to portable, battery-operated sources of T-rays, or terahertz radiation. By doing so, the researchers, led by Ulrich Welp of Argonne's Materials Science Division, have successfully bridged the "terahertz gap" – scientists' name for the range of frequencies between microwaves (on the lower side) and infrared (on the higher side) of the electromagnetic spectrum.
While scientists and engineers have produced microwave radiation using conventional electric circuits for more than 50 years, Welp said, terahertz radiation could not be generated that way because of the physical limitations of the semiconducting circuit components.
"Right around 1 terahertz, you have a range of frequencies where there have never been any good solid-state sources," he added. "You can make those frequencies if you are willing to put together a whole table full of expensive equipment, but now we've been able to make a simple, compact solid-state source."
Unlike far more energetic X-rays, T-rays do not have sufficient energy to "ionize" an atom by knocking loose one of its electrons. This ionization causes the cellular damage that can lead to radiation sickness or cancer. Since T-rays are non-ionizing radiation, like radio waves or visible light, people exposed to terahertz radiation will suffer no ill effects. Furthermore, although terahertz radiation does not penetrate through metals and water, it does penetrate through many common materials, such as leather, fabric, cardboard and paper.
These qualities make terahertz devices one of the most promising new technologies for airport and national security. Unlike today's metal or X-ray detectors, which can identify only a few obviously dangerous materials, checkpoints that look instead at T-ray absorption patterns could not only detect but also identify a much wider variety of hazardous or illegal substances.
T-rays can also penetrate the human body by almost half a centimeter, and they have already begun to enable doctors to better detect and treat certain types of cancers, especially those of the skin and breast, Welp said. Dentists could also use T-rays to image their patients' teeth.
The new T-ray sources created at Argonne use high-temperature superconducting crystals grown at the University of Tsukuba in Japan. These crystals comprise stacks of so-called Josephson junctions that exhibit a unique electrical property: when an external voltage is applied, an alternating current will flow back and forth across the junctions at a frequency proportional to the strength of the voltage; this phenomenon is known as the Josephson effect.
These alternating currents then produce electromagnetic fields whose frequency is tuned by the applied voltage. Even a small voltage – around two millivolts per junction – can induce frequencies in the terahertz range, according to Welp.
Since each of these junctions is tiny – a human hair is roughly 10,000 times as thick – the researchers were able to stack approximately 1,000 of them on top of each other in order to generate a more powerful signal. However, even though each junction would oscillate with the same frequency, the researchers needed to find a way to make them all radiate in phase.
"That's been the challenge all along," Welp said. "If one junction oscillates up while another junction oscillates down, they'll cancel each other out and you won't get anything."
In order to synchronize the signal, Argonne physicist Alexei Koshelev suggested that the stacks of Josephson junctions should be shaped into resonant cavities, which visiting scientist Lufti Ozyuzer of the Izmir Institute of Technology, Turkey, and graduate student Cihan Kurter then fashioned. When the width of the cavities was precisely tuned to the frequencies set by the voltage, the natural resonances of the structure synchronized the oscillations and thus amplified the T-ray output, in a method similar to the production of light in a laser.
"Once you apply the voltage," Welp said, "some junctions will start to oscillate. If those have the proper frequency, an oscillating electric field will grow in the cavity, which will pull in more and more and more of the other junctions, until in the end we have the entire stack synchronized."
By keeping the length and thickness of the cavities constant while varying their width between 40 and 100 micrometers, the researchers were able to generate frequencies from 0.4 to 0.85 terahertz at a signal power of up to 0.5 microwatts. Welp hopes to expand the range of available frequencies and to increase the strength of the signal by making the Josephson cavities longer or by linking them in arrays.
"The more power you have, the easier it is to adopt this technology for all sorts of applications," he said. "Our data indicate that the power stored in the resonant cavities is significantly larger than the detected values, though we need to improve the extraction efficiency. If we can get the signal strength up to 1 milliwatt, it will be a great success."
Collaborators on this research were Lutfi Ozyuzer, Alexei Koshelev, Cihan Kurter, Nachappa (sami) Gopalsami, Qing'An Li, Ken Gray, Wai-Kwong Kwok and Ulrich Welp of Argonne; Masashi Tachiki from the University of Tokyo; Kazuo Kadowaki, Takashi Yamamoto, Hidetoshi Minami and Hayato Yamaguchi from the University of Tsukuba; and Takashi Tachiki from the National Defense Academy of Japan.
The research was supported by DOE's Office of Basic Energy Sciences and by Argonne's Laboratory Directed Research and Development funds.
A scientific paper based on their research, "Emission of Coherent THz Radiation from Superconductors," appears in the November 23 issue of Science.
Adapted from materials provided by DOE/Argonne National Laboratory.

Fausto Intilla

www.oloscience.com

FED-TVs With Carbon Nanotube Technology Could Supersede Plasma And LCD Flat Screens

Source:

http://www.sciencedaily.com/releases/2007/11/071121094629.htm

ScienceDaily (Nov. 23, 2007) — Just as silicon is the wonder material for the computer age, carbon nanotubes will most likely be the materials responsible for the next evolutionary step in electronics and computing. Their extraordinary properties have identified them as having the potential to revolutionise many technologies.
In particular, it is widely believed that carbon nanotubes will take electronic devices to the next level. Many people expect the hugely popular LCD and plasma screens of today to be replaced by field emission flat screen displays (FED-TV). FED-TV's take all the best aspects of CRT's, LCD's and plasma TV's and roll them into a single package. While the technology exists, manufacturers are at present unable to compete with LCD's and plasma displays on a cost basis. However, carbon nanotubes have the ability to change all that.
In order to incorporate carbon nanotubes into devices like these field emission flat screen displays, an intimate knowledge of the properties of various forms of carbon nanotubes is invaluable. Researchers from University of Latvia, University College Cork, Trinity College Dublin, University of London and Mid Sweden University have just published work characterizing the conductive and field emission properties of single and multi walled carbon nanotubes.
In this research the conductive and field emission properties of individual single and multi-walled carbon nanotubes were assessed using an in-situ transmission electron microscope-scanning tunnelling microscope (TEM-STM) technique. The nanotubes were grown by chemical vapour and supercritical fluid deposition techniques.
Experimental field emission characteristics for all carbon nanotubes investigated fitted well to the Fowler-Nordheim equation when different work functions were applied. Differences in field emission and conductive properties are analysed and related to the structure of the carbon nanotubes. The method presented can be applied in order to make in situ selection of carbon nanotubes with desired properties for specific electronic applications.
The researchers found that conductivity and field emission properties were nanotube structure dependent. The structure of the outer layers and whether or not the nanotubes were filled with C60 molecules were key factors in determining the properties of the carbon nanotubes.
These findings make a significant contribution to the understanding of the structure/property relationships for carbon nanotubes, which in turn bring the next generation flat panel televisions and monitors a bit closer to our lounge rooms and offices.
Further details of the work by Jana Andzane, Joseph M. Tobin, Zhonglai Li, Juris Prikulis, Mark Baxendale, Håkan Olin, Justin D. Holmes and Donats Erts were published by AZoJono at http://www.azonano.com/Details.asp?ArticleID=2038.
Adapted from materials provided by AZoNetwork.

Fausto Intilla
www.oloscience.com

3-D Photonic Crystals Will Revolutionize Telecommunications

Source:

http://www.sciencedaily.com/releases/2007/11/071120104550.htm

ScienceDaily (Nov. 21, 2007) — Smaller, faster, more efficient: BASF research scientists are helping to revolutionize the future world of telecommunications – with the aid of three-dimensional photonic crystals. In a three-year project, BASF is researching into the development of these crystals together with partners such as Hanover Laser Center, Thales Aerospace Division, Photon Design Ltd., the Technical University of Denmark and the Ecole Nationale Supérieure des Télécommunications de Bretagne. By the end of 2008, the partners in the "NewTon" project expect to have developed the first functional components of this new technology. The long-term goal is to use three-dimensional photonic crystals as construction elements in telecommunication. Half of the project is being funded by the European Union.
Many times more information can be transmitted by light in the same time as has so far been possible with electricity. This is why telephone conversations, websites, photographs or music, for example, are now increasingly being transmitted in optical fibers. At present, however, this technology still has one drawback at the "network nodes". Indeed, at these nodes the routing of the information to the end-user is still done electrically, because no competitive, compact all-optical routing processor is yet available. This costs time and energy.
This is where the research activities of BASF and its partners come into the picture. They are developing a photonic crystal capable of reflecting only single colors of the white light depending on the observation angle. This phenomenon is known from nature: the splendid, shimmering colors on butterfly wings derive from the properties of photonic crystals.
"A structured three-dimensional photonic crystal could be the key component for a compact optical semiconductor or even for an all-optical routing processor", is the opinion of Dr. Reinhold J. Leyrer who is BASF’s project leader in Polymer Research division. "Converting optical signals into electrical signals would then be superfluous". But the scientists first have to develop a stable, structured three-dimensional photonic crystal. And exactly this is the goal of the EU project "NewTon". This kind of basic research projects are especially suited to activate the European scientific competence, in order to strengthen the competitiveness of the whole region and of all involved industrial branches.
The production of these crystals is based on aqueous dispersions, a key competence of BASF. These dispersions contain polymer spherical particles measuring about 200 nanometers which, when the fluid evaporates, are forming a homogeneous protective film as it is expected with the paints. Depending from the chemical structure of the polymer particles they can also arrange themselves into a regular lattice structure, forming a crystal.
The challenge facing the Ludwigshafen scientists is to enlarge the polymer particles contained in the dispersions to 1000 nanometers in such a way, that they all have exactly the same diameter. Using emulsion polymerization, they also apply an additional structure measuring less than 20 nanometers onto the polystyrene particles. The intention is to develop the most stable possible, large volume, three-dimensional crystal into which one of the project partners will then introduce the desired structure, the so called "defects".
Light at certain wavelengths then travels along these defects and even around sharp corners: the photonic crystal then acts as a photoconductor and takes the control over the propagation of light. The resulting structured crystal lattice is used in the further manufacturing process as a template, as the scientists call it. The spaces between the polymer spherical particles in the crystal lattice are filled with silicon. The researchers then "burn" the polymer particles out of the lattice. The result: a stable structure that is a mirror image of the original crystal. Crystals of this type could be used as components for an all-optical routing processor in telecommunications.
Manufacturers of components for telecommunication systems would benefit most from the use of photonic crystals. Since the crystals are smaller than electronic components, equipment would also become increasingly smaller and cheaper – while simultaneously offering improved performance. Components and equipment based on photonic crystals would also be more resistant and less vulnerable to electromagnetic radiation. End users will gain from these advances. In the long term, transmitting information through electrical signals will restrict speed and transmission capacity in telecommunications. The long-term goal is therefore to develop a communications technology based entirely on transmitting information by light waves. The research activities of the "NewTon" project are laying the foundations for this scenario.
Adapted from materials provided by BASF Aktiengesellschaft.

Fausto Intilla
www.oloscience.com

Lung-on-a-chip Leads To New Insights On Pulmonary Diseases

Source:

http://www.sciencedaily.com/releases/2007/11/071119143651.htm

ScienceDaily (Nov. 20, 2007) — A new "lung-on-a-chip" developed at the University of Michigan mimics the fluid mechanics of the real thing on a plastic wafer just bigger than a quarter. It allows researchers to grow lung airway cells that act more like they're in a human body instead of a Petri dish.

Biomedical engineers used the device to show that the respiratory crackles stethoscopes pick up in patients with diseases including asthma, cystic fibrosis, pneumonia and congestive heart failure aren't just symptoms, but may actually cause lung damage.
"Our lung-on-a-chip causes the cells to really become lung-like in terms of function and protein secretion. They form the tight tissue connections that they do in the human lung. That doesn't happen in a dish. This device gives you the convenience and control of a dish but in physical conditions that are more like the body," said Shuichi Takayama, associate professor of biomedical engineering and principal investigator on this study.
Takayama believes this is the first lung-on-a-chip. It's the same size as the part of the lung it simulates, the smallest airway branches.
The researchers were able to recreate the sound of respiratory crackles on the chip. And they measured and watched the destruction associated with the crackling on the surrounding cells.
The crackling is the sound of a breath of air opening airways that are clogged with thick fluid plugs. The fluid plugs form more frequently in patients with lung diseases that block the production of a fluid-thinning protein or narrow the airways. The plugs burst when air expands the lungs during breathing.
Doctors have considered the crackling sound more as a symptom or red flag, explained Dr. James Grotberg, a co-author of the study who is a professor of biomedical engineering in the College of Engineering and the Medical School.
Now, the plugs that cause the crackles appear to be a cause in addition to an effect.
"We've shown that these liquid plugs are injurious, particularly when they rupture" Grotberg said. "The rupture sends a very strong stress wave onto the cells. What's interesting is that the forces from the rupture are large in one place and small in another and those two places are close to each other. So you have a very steep gradient in forces and that's what shreds the cells."
To the surrounding cells, the bursts are like little sticks of exploding dynamite, Grotberg said.
The lung-on-a-chip that allowed the scientists to demonstrate this is made of two rubber sheets with a groove etched across their length. Their grooved sides are stuck together, with a porous sheet of polyester between them. The polyester allows the device to function as two separate chambers.
Engineers flooded both chambers with nourishing liquid while they were growing the lung cells in the device. Then, they emptied the top chamber to simulate an airway. That's when the lung cells started to develop further than they do in a dish. They formed tighter tissue bonds and secreted airway proteins as if they were part of a real lung.
Once the cells were sufficiently developed on the chip, Takayama and his colleagues did the control part of the experiment. They ran liquid through the chip channels and then air before testing to see if the lung cells were still healthy. They were.
Then they turned on the "microfabricated plug generator," which was connected to the cell culture chamber on the same chip. The plug generator is a vial of liquid into which the scientists pump air in such a way that drops of liquid enter the mock airways of the chip and eventually burst. They tested for periods of 10 minutes and found that at least 24 percent of the cells had died after persistent exposure to bursting liquid plugs. They observed more cell damage with more frequent plug bursts.
Takayama is also an associate professor of macromolecular science and engineering. The paper is called "Acoustically detectable cellular-level lung injury induced by fluid mechanical stresses in microfluidic airway systems." Co-authors include Biomedical Engineering Research Fellow Dongeun Huh, Biomedical Engineering Senior Research Fellow Hideki Fujioka, Biomedical Engineering Research Fellow Yi-Chung Tung, Post-doctoral researcher Nobuyuki Futai, and Adjunct Professor of Internal Medicine Robert Paine III.
A paper on the findings is published in the Nov.12 early edition of the Proceedings of the National Academy of Sciences.
Adapted from materials provided by University of Michigan.

Fausto Intilla

www.oloscience.com

Thinking Makes It So: Science Extends Reach Of Prosthetic Arms

Source:

http://www.sciencedaily.com/releases/2007/11/071111182522.htm

ScienceDaily (Nov. 12, 2007) — Motorized prosthetic arms can help amputees regain some function, but these devices take time to learn to use and are limited in the number of movements they provide.

Todd A. Kuiken, M.D., Ph.D., a physiatrist at the Rehabilitation Institute of Chicago and professor at Northwestern University, has pioneered a technique known as targeted muscle reinnervation (TMR), which allows a prosthetic arm to respond directly to the brain’s signals, making it much easier to use than traditional motorized prosthetics. This technique, still under development, allows wearers to open and close their artificial hands and bend and straighten their artificial elbows nearly as naturally as their own arms.
“The idea is that when you lose your arm, you lose the motors, the muscles and the structural elements of the bones,” Kuiken explained. “But the control information should still be there in the residual nerves.” He decided to take the residual nerves, which once carried the commands from the brain to produce arm, wrist and hand movements, and connect them to the chest muscles so that the signals can be used to move the artificial limb.
Nearly a dozen patients who have undergone TMR so far have motorized prosthetic arms that produce two arm movements: open and close hand and bend and straighten elbow. But in a new study from the Journal of Neurophysiology, published by The American Physiological Society, Kuiken and his colleagues demonstrate that TMR has the potential to provide an even greater number of arm and hand movements, beyond the four they’ve already achieved. The researchers have begun work with two U.S. Army medical centers to help soldiers who have lost limbs.
Redirects nerves
Kuiken first got the idea for TMR when he was a graduate student during the 1980s. In his first patient, Kuiken took four nerves that had gone to the amputated arm and redirected them to the patient’s chest muscles. As a result, when the patient wants to close his hand – a hand that is no longer there – the impulse travels down the nerve, into his chest and causes the chest muscle to contract.
The next step was to use the muscle contraction in the chest to move the prosthetic arm. This was accomplished with the help of an electromyogram (EMG), which picks up the electrical signal that the muscle emits when it contracts.
The signal is directed to a microprocessor in the artificial arm which decodes the signal and tells the arm what to do. In their work thus far, Kuiken and his colleagues have programmed the processor in the prosthetic arm to recognize four signals to produce two arm movements: open and close hand and bend and straighten elbow.
The result? When the patient thinks ‘close hand’ the hand closes. Contrast this with current motorized prosthetic arm technology: The patient has to learn to use new muscle groups to move the prosthetic arm; can perform only one movement at a time; and must contract two muscles at once to achieve a new movement.
“It’s not very common to flex your chest muscle to close your hand or bend your wrist,” said Kuiken. “Quite frankly, most people with a unilateral shoulder disarticulation amputation don’t wear a prosthesis at all: It’s just too cumbersome.”
More moves
While TMR is more intuitive and natural, Kuiken and his team wanted to see if they could extract more of the wealth of information from the electrical signals produced by the nerves and chest muscles and harness it to provide a greater number of hand and arm movements.
In the study published in the Journal of Neurophysiology*, they placed between 79-128 electrodes from the EMG onto the chest muscles of five patients to see if they could identify the unique EMG patterns emitted with 16 different elbow, wrist, hand, thumb and finger movements they asked the patients to perform. The EMG signals from each of the 16 movements were analyzed using advanced signal processing techniques. The study found that the researchers could recognize the signals associated with the different arm movements with 95% accuracy.
The next step is to use this information to program these new moves into the microprocessor of the artificial arm, so that instead of just opening and closing a hand and bending and straightening an elbow, now the signals can produce various hand grasp patterns, such as the one needed to hold a baseball, pick up a pen or grasp a tool.
May benefit soldiers
Kuiken and his colleagues have begun to work with the military at Brooke Army Medical Center at Fort Sam Houston in Texas and the Walter Reed Army Hospital in Washington, D.C. to apply this technology to soldiers who have lost limbs.
“We’re excited to move forward in doing this surgery with our soldiers some day,” he said. “We’ve been able to demonstrate remarkable control of artificial limbs and it’s an exciting neural machine interface that provides a lot of hope.”
There are a couple of additional things to note in the work of Kuiken and his colleagues: They performed nerve transfer surgery 9-15 months after the injury that led to amputation, showing that these neural pathways remain intact, even when they have not been used for awhile.
Also, when the researchers touch these patients on their chests, the patients say it feels like they are being touched somewhere on their arm or hand -- the arm or hand that is no longer there. That’s not really surprising, because the brain receives an impulse from a nerve that used to go to the arm. The brain doesn’t know the nerve is now embedded in a different muscle, and interprets this touch as it always has.
*The study, entitled “Decoding a new neural-machine interface for control of artificial limbs,” was conducted by Ping Zhou, Madeleine M. Lowery, Kevin B. Englehart, He Huang, Guanglin Li, Levi Hargrove, Julius P.A. Dewald and Kuiken, all of Northwestern University and the Rehabilitation Institute of Chicago. Hargrove is also affiliated with the University of New Brunswick, Canada and Lowery is also affiliated with University College Dublin, Ireland.
Adapted from materials provided by American Physiological Society.

Fausto Intilla

www.oloscience.com

'Electronic Nose' Could Detect Hazards

Source:

http://www.sciencedaily.com/releases/2007/11/071109171606.htm

ScienceDaily (Nov. 12, 2007) — A tiny "electronic nose" that MIT researchers have engineered with a novel inkjet printing method could be used to detect hazards including carbon monoxide, harmful industrial solvents and explosives.

Led by MIT professor Harry Tuller, the researchers have devised a way to print thin sensor films onto a microchip, a process that could eventually allow for mass production of highly sensitive gas detectors.
"Mass production would be an enormous breakthrough for this kind of gas sensing technology," said Tuller, a professor in the Department of Materials Science and Engineering (MSE), who is presenting the research Oct. 30 at the Composites at Lake Louise Conference in Alberta, Canada.
The prototype sensor, created by Tuller, postdoctoral fellow Kathy Sahner and graduate student Woo Chul Jung, members of MIT's Electroceramics Group in MSE, consists of thin layers of hollow spheres made of the ceramic material barium carbonate, which can detect a range of gases. Using a specialized inkjet print head, tiny droplets of barium carbonate or other gas-sensitive materials can be rapidly deposited onto a surface, in any pattern the researchers design.
The miniature, low-cost detector could be used in a variety of settings, from an industrial workplace to an air-conditioning system to a car's exhaust system, according to Tuller. "There are many reasons why it's important to monitor our chemical environment," he said.
For a sensor to be useful, it must be able to distinguish between gases. For example, a sensor at an airport would need to know the difference between a toxic chemical and perfume, Tuller said. To achieve this, sensors should have an array of films that each respond differently to different gases. This is similar to the way the human sense of smell works, Tuller explained.
"The way we distinguish between coffee's and fish's odor is not that we have one sensor designed to detect coffee and one designed to detect fish, but our nose contains arrays of sensors sensitive to various chemicals. Over time, we train ourselves to know that a certain distribution of vapors corresponds to coffee," he said.
In previous work designed to detect nitrogen oxide (NOx) emissions from diesel exhaust, the researchers created sensors consisting of flat, thin layers of barium carbonate deposited on quartz chips. However, the films were not sensitive enough, and the team decided they needed more porous films with a larger surface area.
To create more texture, they applied the barium carbonate to a layer of microspheres, hollow balls less than a micrometer in diameter made of a plastic polymer. When the microspheres are burned away, a textured, highly porous layer of gas-sensitive film is left behind.
The resulting film, tens of nanometers (billionths of a meter) thick, is much more sensitive than flat films because it allows the gas to readily permeate through the film and interact with a much larger active surface area.
At first, the researchers used a pipette to deposit the barium carbonate and microspheres. However, this process proved time-consuming and difficult to control.
To improve production efficiency, the researchers took advantage of a programmable Hewlett-Packard inkjet print head located in the MIT Laboratory of Organic Optics and Electronics. The inkjet print head, like that in a regular inkjet printer, can deposit materials very quickly and controllably. The special gas-sensitive "inks" used in this work were optimized for printing by Amy Leung, an MIT sophomore in chemical engineering.
This allows the researchers to rapidly produce many small, identical chips containing geometrically well-defined gas-sensing films with micrometer dimensions. Patterns of different gas-sensitive inks, just as in a color printer, can be easily generated to form arrays with very little ink required per sensor.
In future studies, the team hopes to create large arrays of gas-sensitive films with controlled three-dimensional shapes and morphologies.
The research is funded by the National Science Foundation.
Adapted from materials provided by Massachusetts Institute of Technology.

Fausto Intilla

www.oloscience.com

New Technology Can Be Operated By Thought

Source:

http://www.sciencedaily.com/releases/2007/11/071107210708.htm

ScienceDaily (Nov. 9, 2007) — Neuroscientists have significantly advanced brain-machine interface (BMI) technology to the point where severely handicapped people who cannot contract even one leg or arm muscle now can independently compose and send e-mails and operate a TV in their homes. They are using only their thoughts to execute these actions.

Thanks to the rapid pace of research on the BMI, one day these and other individuals may be able to feed themselves with a robotic arm and hand that moves according to their mental commands.
"Our work has shown how important the learning process is when using brain-controlled devices," says Andrew Schwartz, PhD, of the University of Pittsburgh. "By permitting the subject to adaptively recode the generated neural activity, the overall performance of the device is dramatically increased.
"Furthermore, as we have progressed in this work, it has become apparent that the basic idea of 'intention' during learning is very important and can be addressed by the direct observation of the neuronal transformations taking place during this fundamental processing," Schwartz says.
Among the research institutions conducting cutting-edge research on the BMI is the University of Pittsburgh, where scientists recently succeeded in developing the technology that allows a rhesus macaque monkey to mentally control a robotic arm to feed itself pieces of fruit. The robotic arm's fast and smooth movements were triggered by electrical signals that were generated in the monkey's brain when the animal thought about an action.
In previous studies, this lab developed the technology to tap a macaque monkey's motor cortical neural activity making it possible for the animal to use its thoughts to control a robotic arm to reach for food targets presented in 3D space.
In the Pittsburgh lab's latest studies, macaque monkeys not only mentally guided a robotic arm to pieces of food but also opened and closed the robotic arm's hand, or gripper, to retrieve them. Just by thinking about picking up and bringing the fruit to its mouth, the animal fed itself.
The monkey's own arm and hand did not move while it manipulated the two-finger gripper at the end of the robotic arm. The animal used its own sight for feedback about the accuracy of the robotic arm's actions as it mentally moved the gripper to within one-half centimeter of a piece of fruit.
"The monkey developed a great deal of skill using this physical device," says Meel Velliste, PhD. "We are in the process of extending this type of control to a more sophisticated wrist and hand for the performance of dexterous tasks."
Velliste and the other members of the Pittsburgh research team point out that imparting skill and dexterity to these devices will help amputees and paralyzed patients to perform everyday tasks.
The animal's thoughts emitted electrical signals that were recorded by tiny electrodes that the scientists had implanted in the monkey's motor cortex. A computer-decoding algorithm translated the signals into the robotic arm and gripper's movements.
In another study, a Washington University School of Medicine research team has generated new information about a long-held theory about the separate functions and responsibilities of the left brain and the right brain. In the process, the researchers, led by Eric Leuthardt, PhD, and his graduate students Kimberly Wisneski and Nick Anderson, have applied their findings to a new neuroprosthetic strategy to improve the rehabilitation of stroke and trauma victims who have suffered damage to either the right or left half of the brain.
"Classic understanding of brain function has asserted that one hemisphere, or one side of the brain, controls arm and leg movement on the opposite side of the body," Wisneski explains.
The team's new findings indicated that if the left hemisphere were damaged, the right side of the brain still had electrical signals that could be used to trigger right-sided arm and leg movement.
The scientists recorded the brain activity of six epilepsy patients in which electrodes were placed over the surface of their brain for reasons that were not connected to the purpose of the study. (The intracranial electrode arrays were implanted on the surface of each patient's brain to locate the brain areas that were involved with the patient's seizures.) "This access provided us with insights that could not be obtained using other methods," Leuthardt says.
The team recorded electrocorticographic signals while each patient opened and closed his or her hands. These recordings revealed brain activity in the hemisphere on the same side of the body in which movement was occurring. These same-side signals occurred at a lower frequency than did the signals emitted in the hemisphere opposite to the moving side of the body.
In addition, these same-side signals were emitted in spatially distinct areas of the brain and earlier in time in comparison to the hemispheric signals recorded for opposite-side hand movement.
"This evidence demonstrates that the brain encodes information regarding planning for movements of the same-sided limb and that this information is encoded in a way that is unique from that corresponding to opposite-side limb movements," Wisneski says.
The team next determined how these results could be used to improve the rehabilitation of stroke and brain injury patients. Their focus: the brain computer interface (BCI), an external device that was designed to benefit patients with spinal cord injury and other disorders that did not affect the brain. The BCI enables individuals to control with their thoughts alone a cursor on a computer screen, a wheelchair, or a robotic arm.
To benefit stroke and brain injury patients, the BCI would have to be adapted to respond to signals from only one side of the brain.
"To allow these patients to benefit from the use of a brain-computer interface, signals for control for two sides of the body must be acquired from the single functioning hemisphere alone," Leuthardt says. "In this paradigm, one side of the body -- the side opposite to the unaffected half of the brain -- would be controlled through normal physiologic pathways, and the other side of the body -- the side affected by the stroke and on the same side as the unaffected hemisphere -- would be controlled through neuroprosthetic assistance using same-side signals from the undamaged hemisphere."
Other scientists are studying the phenomenon in which neurons are active in the brain's motor cortex, not only when an individual bends a leg but also when he or she observes other people while moving their legs. This neural mechanism may help explain the development of innate skills such as speech and new motor skills such as a golf swing.
Graduate student Dennis Tkach and colleagues at University of Chicago hope to tap this neural mechanism to modify BMI systems for use by people who are paralyzed from spinal cord injury or related trauma. Currently the BMI's functioning depends on mathematical maps that connect brain cell activity to the action -- arm or leg movement, for example -- that the system is designed to replace.
Tkach says that the phenomenon of congruent neural activity may provide the mathematical maps of these paralyzed patients. "The existence of these neurons offers the means of creating this mapping by relating neural activity of the patient to an action observed by that patient," he says. "The neural activity is congruent because the way that the neurons fire during observation of familiar action is the same as the way they fire when the individual is performing that same action."
The University of Chicago study, which was conducted with rhesus monkeys, was the first to analyze a neural system that showed congruent activity with movement on a single cell level in the primary motor cortex.
The monkeys were trained to perform a video task in a two-dimensional, horizontal workspace located in front of them. They guided a circular cursor to a square target. Both the cursor and the target were projected onto the workspace. The animals controlled the cursor by moving an exoskeletal robot arm in which their active arm rested.
They were then trained to relax and watch a playback of the task they had just performed. During the playback, the monkeys saw either or both the target and the cursor on the screen.
"We varied visibility of the video task components in an attempt to gain a better understanding of what facilitates the neural congruency between observation and action," Tkach says. "The study showed that the presence of the goal of an action bears a greater impact on the strength of this congruence, while the observation of the motion to this goal carries minimal importance."
This result emphasized the importance of the goal as the facilitator of this action-like neural response, Tkach says.
The brain cell activity patterns were recorded from arrays of 100 electrodes surgically implanted in the monkeys' motor cortical areas. Because of these arrays, Tkach was able to obtain simultaneous neural activity data from a population of single cells along with a more global neural signal. Analyzing the data, he noted that the activity patterns of the neurons during the observation period correlated highly with the cells' activity patterns when the animal was using its right arm to guide the cursor.
"Our results lead us to believe that when presented with the observation of a familiar action the monkeys inadvertently generate a motor command that is very similar to one that would occur if the animal were to execute the behavior," Tkach says. The congruence of this motor command to the "actual" one was not an all-or-nothing phenomenon but instead spanned a continuum that was contingent upon the components of the observed action that was present.
In other work, Wadsworth Center scientists in Albany, N.Y., have succeeded in developing a BCI that provided people who are severely disabled with the ability to use their personal computers. For example, they were able to word-process, send e-mail messages, and remotely turn on or off the lights or TV in their homes. In the future, even more environmental control options will be available, says Eric Sellers, PhD.
The Wadsworth Center BCI system enabled a scientist with advanced amyotrophic lateral sclerosis (ALS), to communicate by e-mail with his research team. "It has allowed him to continue to direct a highly successful NIH-funded medical research program," Sellers says. "The initial results indicate that the BCI can function without close technical oversight and can improve communication ability and quality of life. This initial success suggests that a home BCI system can be of practical value for people with severe motor disabilities and that caregivers without special expertise can learn to support it."
Five severely disabled people have participated in the Wadsworth research program that evaluates the center's BCI system. The first participant, the 49-year-old scientist with ALS, has been unable to move any muscles in his body except for his eyes. For up to five to seven hours every day since February 2006, he has worn a simple electrode cap on his scalp that picks up the electrical activity generated by his brain. The cap recorded electroencephalographic (EEG, or brain wave) activity at eight scalp locations.
The user's brain waves were translated into simulated keystrokes. Software developed at Wadsworth presented rows and columns of a 72-element, 8" x 9" matrix that flashed in random order while the user paid attention to the element that he or she wanted to select. The software recognized that element and executed the appropriate keystroke. With this design, the patient could use the entire keyboard.
Sellers says that caregivers and family members learned to place the electrode cap on patients' scalps, enable the software, and generally maintain the system, which the researchers monitored remotely via data transferred weekly from patients' homes to the lab. To date, a total of five people with ALS have used the Wadsworth system in their homes.
In addition, the Wadsworth Center team has tested protocols in the laboratory that extend BCI functionality to benefit people with limited eye mobility, poor visual acuity, or difficulty maintaining gaze, impairments that can occur with severe motor disorders such as ALS, brainstem stroke, or cerebral palsy. For these individuals, the scientists have been developing a BCI system that uses auditory rather than visual stimuli.
In the auditory BCI system, the rows and columns of a 6" x 6" matrix of 36 letters and numbers are represented by six environmental sounds. For each selection, the user paid attention to the sound representing the column or row containing the desired choice. Thus far, most of the people who tested this auditory system in the lab used it with accuracy sufficient to support effective BCI operation.
The researchers also have been developing a BCI system that uses sensorimotor rhythms (SMRs), oscillations in the EEG recorded from the scalp over the sensorimotor cortex. The SMRs provided simple communication capabilities, and the people learned to use SMRs to control a computer cursor in one or two dimensions.
Adapted from materials provided by Society for Neuroscience.

Fausto Intilla

www.oloscience.com

New Mini-sensor May Have Biomedical And Security Applications

Source:

http://www.sciencedaily.com/releases/2007/11/071101150116.htm

ScienceDaily (Nov. 6, 2007) — A tiny sensor that can detect magnetic field changes as small as 70 femtoteslas-equivalent to the brain waves of a person daydreaming-has been demonstrated at the National Institute of Standards and Technology (NIST). The sensor could be battery-operated and could reduce the costs of non-invasive biomagnetic measurements such as fetal heart monitoring. The device also may have applications such as homeland security screening for explosives.

Described in the November issue of Nature Photonics,* the prototype device is almost 1000 times more sensitive than NIST's original chip-scale magnetometer demonstrated in 2004 and is based on a different operating principle. Its performance puts it within reach of matching the current gold standard for magnetic sensors, so-called superconducting quantum interference devices or SQUIDs. These devices can sense changes in the 3- to 40-femtotesla range but must be cooled to very low (cryogenic) temperatures, making them much larger, power hungry, and more expensive.
The NIST prototype consists of a single low-power (milliwatt) infrared laser and a rice-grain-sized container with dimensions of 3 by 2 by 1 millimeters. The container holds about 100 billion rubidium atoms in gas form. As the laser beam passes through the atomic vapor, scientists measure the transmitted optical power while varying the strength of a magnetic field applied perpendicular to the beam. The amount of laser light absorbed by the atoms varies predictably with the magnetic field, providing a reference scale for measuring the field. The stronger the magnetic field, the more light is absorbed.
"The small size and high performance of this sensor will open doors to applications that we could previously only dream about," project leader John Kitching says.
The new NIST mini-sensor could reduce the equipment size and costs associated with some non-invasive biomedical tests. (The body's electrical signals that make the heart contract or brain cells fire also simultaneously generate a magnetic field.) The NIST group and collaborators have used a modified version of the original sensor to detect magnetic signals from a mouse heart.**
The new sensor is already powerful enough for fetal heart monitoring; with further work, the sensitivity can likely be improved to a level in the 10 femtotesla range, sufficient for additional applications such as measuring brain activity, the designers say. A femtotesla is one quadrillionth (or a millionth of a billionth) of a tesla, the unit that defines the strength of a magnetic field. For comparison, the Earth's magnetic field is measured in microteslas, and a magnetic resonance imaging (MRI) system operates at several teslas.
To make a complete portable magnetometer, the laser and vapor cell would need to be packaged with miniature optics and a light detector. The vapor cell can be fabricated and assembled on semiconductor wafers using existing techniques for making microelectronics and microelectromechanical systems (MEMS). This design, adapted from a previously developed NIST chip-scale atomic clock, offers the potential for low-cost mass production.
As described in the new paper, NIST scientists demonstrated that the prototype mini-sensor produces a strong signal that changes rapidly with the strength of a magnetic field from the outside world. The device exhibits a consistent minimum level of electromagnetic static, or "white noise," which indicates a stable limit on its overall sensitivity. The authors also estimated that a well-designed compact magnetometer with present sensitivity could operate continuously for weeks on a single AA battery.
Magnetometers need to be designed with applications in mind; smaller vapor cells require less power but are also less sensitive. Thus, an application for which low power is critical would benefit from a very small magnetometer, whereas a larger magnetometer would be more suitable for a different application requiring high sensitivity. The NIST work evaluates the tradeoffs between size, power and performance in a quantifiable way.
"This result suggests that millimeter-scale, low-power, inexpensive, femtotesla magnetometers are feasible ... Such an instrument would greatly expand the range of applications in which atomic magnetometers could be used," the paper states.
The NIST device could be used in a heart monitoring technique known as magnetocardiography (MCG), which is sensitive enough to measure fields of few picoteslas emitted by the fetal heart from small currents in heart muscle cells, providing complementary and perhaps better information than an electrocardiogram. With further improvements, the NIST sensor also might be used in magnetoencephalography (MEG), which measures the magnetic fields produced by electrical activity in the brain, helping to pinpoint tumors or determine function of various parts of the brain. The existing mini-sensor likely will be able to detect some brain activity, such as the signals from alpha waves, which are about 1 picotesla in magnitude at a distance of 1 centimeter from the skull surface, but not the fainter signals from the full range of brain function. (Signals of magnitude 1 picotesla are identifiable with a magnetometer sensitivity of 70 femtotesla per root Hertz.) MCG and MEG offer the advantage of not requiring contrast agents or injected tracers as do other medical procedures such as MRI or positron emission tomography (PET).
Potential NIST collaborators are interested in making a portable MEG helmet that could be worn by epileptics to record brain activity before and during seizures. The devices would be much smaller and lighter than the SQUID helmets currently used for such studies. Kitching said the NIST sensor also may have applications in MRI or in airport screening for explosives based on detection of nuclear quadrupole resonance in nitrogen compounds.
As a non-regulatory agency of the Commerce Department, NIST promotes U.S. innovation and industrial competitiveness by advancing measurement science, standards and technology in ways that enhance economic security and improve our quality of life.
* Vishal Shah, Svenja Knappe, Peter D.D. Schwindt, and John Kitching. Femtotesla Atomic Magnetometry with a Microfabricated Vapor Cell. Nature Photonics. 1 November 2007.
** Brad Lindseth, Peter Schwindt, John Kitching, David Fischer, Vladimir Shusterman. 2007. Non-contact Measurement of Cardiac Electromagnetic Field in Mice Using an Ultra-small Atomic Magnetometer. Feasibility Study. Presented at Computers in Cardiology, Durham, NC, Sept 30-Oct. 3, 2007.
How the NIST Mini-Sensor Works
The NIST compact magnetometer is based on the so-called SERF (spin-exchange relaxation free) principle, which was used by a group at Princeton University in 2003 to enhance the sensitivity of larger, tabletop-sized magnetometers to outperform SQUIDs. The NIST group developed novel approaches and technologies to adapt the SERF concept for tiny and practical devices.
At zero magnetic field, the atoms' electron "spins" (which can be roughly visualized as tiny magnetic arrows pointing through the electrons) all point in the same direction as the laser beam, and the atoms absorb virtually no light. As the magnetic field is increased, the electrons jump to higher-energy levels and their spins go out of sync, causing the atoms to absorb some of the light.
Ordinarily, the atoms would collide randomly and the electron spins would change direction in between collisions, degrading the sensor signal. The SERF approach maintains consistent spins for a relatively long time (10 milliseconds) by combining a low magnetic field with high temperatures of 150 degrees C (302 degrees F). The spins have little time to adjust in between the collisions. Like cars on a highway, the atoms behave more consistently when conditions are crowded.
Adapted from materials provided by National Institute of Standards and Technology.

Fausto Intilla

www.oloscience.com

World's Most Complex Silicon Phased-array Chip Developed

Source:

http://www.sciencedaily.com/releases/2007/10/071030135705.htm

ScienceDaily (Nov. 4, 2007) — UC San Diego electrical engineers have developed the world's most complex “phased array” -- or radio frequency integrated circuit. This DARPA-funded advance is expected to find its way into U.S. defense satellite communication and radar systems. In addition, the innovations in this chip design will likely spill over into commercial applications, such as automotive satellite systems for direct broadcast TV, and new methods for high speed wireless data transfer.

“This is the first 16 element phased array chip that can send at 30-50 GHz. The uniformity and low coupling between the elements, the low current consumption and the small size – it is just 3.2 by 2.6 square millimeters – are all unprecedented. As a whole system, there are many many firsts,” said Gabriel Rebeiz, the electrical engineering professor from the UCSD Jacobs School of Engineering leading the project.
This chip – the UCSD DARPA Smart Q-Band 4x4 Array Transmitter – is strictly a transmitter. “We are working on a chip that can do a transmit and receive function,” said Rebeiz.
“This compact beamforming chip will enable a breakthrough in size, weight, performance and cost in next-generation phased arrays for millimeter-wave military sensor and communication systems,” DARPA officials wrote in a statement.
“DARPA has funded us to try to get everything on a single silicon chip – which would reduce the cost of phased arrays tremendously. In large quantities, this new chip would cost a few dollars to manufacture. Obviously, this is only the transmitter. You still need the receiver but one can easily build the receiver chip based on the designs available in the transmitter chip. Our work addresses the most costly part of the phased array – the 16:1 divider, phase shifters, amplitude controllers and the uniformity and isolation between channels,” said Rebeiz
The chip also contains all the CMOS digital circuits necessary for complete digital control of the phased array, and was done using the commercial Jazz SBC18HX process. This is a first and greatly reduces the fabrication complexity of the phased array. The chip has been designed for use at the defense satellite communications frequency – the Q-band - which goes from 40 to 50 GHz.
“If you take the same design and move it to the 24 or 60 GHz range, you can use it for commercial terrestrial communications,” said Rebeiz who is also a lead on a separate project, funded by Intel and a UC-Discovery Grant, to create silicon CMOS phased array chips that could be embedded into laptops and serve as high speed data transfer tools.
The Intel project is a collaboration between Rebeiz, Larry Larson and Ian Galton – all electrical engineering professors at the UCSD Jacobs School of Engineering. Larson also serves as the chair of the Department of Electrical and Computer Engineering.
“If you wanted to download a large movie file, a base station could find you, zoom onto you, and direct a beam to your receiver chip. This could enable data transfer of hundreds of gigabytes of information very quickly, and without connecting a cable or adhering to the alignment requirements of wireless optical data transfer,” explained Rebeiz who estimated that this kind of system could be available in as little as three years.
Phased Array Background Information
Phased arrays have been around for more than half a century. They are groups of antennas in which the relative phases of the signals that feed them are varied so that the effective radiation pattern of the array is reinforced in a particular direction and suppressed in undesired directions. This property – combined with the fact that radio waves can pass through clouds and most other materials that stymie optical communication systems – has led engineers to use phased arrays for satellite communications, and for detecting incoming airplanes, ships and missiles.
Some phased arrays are larger than highway billboards and the most powerful – used as sophisticated radar, surveillance and communications systems for military aircraft and ships – can cost hundreds of millions of dollars. The high cost has prevented significant spread beyond military and high-end satellite communication applications. Engineers are now working to miniaturize them and fully integrate them into silicon-based electronic systems for both military and commercial applications.
The new UCSD chip packs 16 channels into a 3.2 by 2.6 mm² chip. The input signal is divided on-chip into 16 different paths with equal amplitude and phase using an innovative design, and the phase and gain of each of the 16 channels is controlled electronically to direct the antenna pattern (beam) into a specific direction.
By manipulating the phase, you can steer the beam electronically in nanoseconds. With the amplitude, you control the width of the beam, which is critical, for example, when you send information to from one satellite to another but you don’t want the signal to reach any nearby satellites. And with amplitude and phase control, you can synthesize deep nulls in the antenna pattern so as to greatly reduce the effect of interfering signals from neighboring transmitters.
The work was done by two graduate students, Kwang-Jin Koh and Jason May, both at the Electrical and Computer Engineering Department (ECE) at UCSD. Rebeiz presented the new chip at DARPA TEAM Meeting, August 28-29, 2007 in Chicago, Illinois. Additional details of the chip will be submitted to an academic journal later this year.
Adapted from materials provided by University of California - San Diego.

Fausto Intilla

www.oloscience.com

New Magnet Design Sheds Light On Nanotechnology And Semiconductor Research

Source:

http://www.sciencedaily.com/releases/2007/10/071031152845.htm

ScienceDaily (Oct. 31, 2007) — Engineers at Florida State University's National High Magnetic Field Laboratory have successfully tested a groundbreaking new magnet design that could literally shed new light on nanoscience and semiconductor research.

When the magnet -- called the Split Florida Helix -- is operational in 2010, researchers will have the ability to direct and scatter laser light at a sample not only down the bore, or center, of the magnet, but also from four ports on the sides of the magnet, while still reaching fields above 25 tesla. By comparison, the highest-field split magnet in the world attains 18 tesla. "Tesla" is a measurement of the strength of a magnetic field; 1 tesla is equal to 20,000 times the Earth's magnetic field.
Magnetism is a critical component of a surprising number of modern technologies, including MRIs and disk drives, and high-field magnets stand beside lasers and microscopes as essential research tools for probing the mysteries of nature. With this new magnet, scientists will be able to expand the scope of their experimental approach, learning more about the intrinsic properties of materials by shining light on crystals from angles not previously available in such high magnetic fields. In materials research, scientists look at which kinds of light are absorbed or reflected at different crystal angles, giving them insight into the fundamental electronic structure of matter.
The Split Florida Helix design represents a significant accomplishment for the magnet lab's engineering staff. High magnetic fields exert tremendous forces inside the magnet, and those forces are directed at the small space in the middle . . . that's where Mag Lab engineers cut big holes in it.
"You have enough to worry about with traditional magnets, and then you try to cut huge holes from all four sides from which you can access the magnet," said lab engineer Jack Toth, who is spearheading the project. "Basically, near the midplane, more than half of the magnet structure is cut away for the access ports, and it's still supposed to work and make high magnetic fields."
Magnet engineers worldwide have been trying to solve the problem of creating a magnet with side access at the midsection, but they have met with little success in higher fields. Magnets are created by packing together dense, high-performance copper alloys and running a current through them, so carving out empty space at the heart of a magnet presents a huge engineering challenge.
Instead of fashioning a tiny pinhole to create as little disruption as possible, as other labs have tried, Toth and his team created a design with four big elliptical ports crossing right through the midsection of the magnet. The ports open 50 percent of the total space available for experiments, a capability the laboratory's visiting scientists have long desired.
"It's different from any traditional magnet that we've ever built before, and even the fabrication of our new parts was very challenging," Toth said. "In search of a vendor for manufacturing the prototypes, I had phone conversations where people would promise me, 'Jack, we looked at it from every possible angle and this part is impossible to machine.'"
Of course, that wasn't the case, and the model coil, crafted from a mix of copper-beryllium blocks and copper-silver plates, met expectations during its testing in a field higher than 32 tesla with no damage to its parts.
Though the National Science Foundation-funded model has reached an important milestone, years of work will go into the final product. The lab hopes to have a working magnet for its User Program by 2010, and other research facilities have expressed great interest in having split magnets that can generate high magnetic fields.
Adapted from materials provided by Florida State University.

Fausto Intilla

www.oloscience.com