(NanoRealm) - A team of scientists has developed a way to control the direction of light on the nanoscale, by developing miniaturized television aerials made from gold nanorods, which can pave the way for quantum computing networks in the future.

At the moment, quantum physicists use cumbersome apparatus to try to keep track of photons, for instance, building large vacuum cavities with mirrored walls to guide light.

"It's funny that to control the small quantum world, you need huge pieces of equipment," said Holger Hofmann, at the Department of Quantum Matter at Hiroshima University in Japan.

Now, according to a report in Nature News, Hofmann and his colleagues have developed a way to control the direction of light on the nanoscale.

Their technique is based on the workings of the 'Yagi-Uda' antenna commonly used to transmit and detect radio waves and often seen on rooftops as television aerials.

Hofmann stumbled on the idea by accident, while teaching his electromagnetism class how antennas work.

"The textbook didn't explain it well, and while trying to come up with my own picture, I realized that the same technique could work on the nanoscale," he said.

A standard Yagi-Uda antenna is made up of a set of parallel metal rods that gradually decrease in length.

An electrical signal is fed into the second longest rod, setting it vibrating and producing a driving electromagnetic wave that spreads out in all directions.

This stimulates the neighbouring rods to oscillate and emit secondary waves.

Both the length and spacing of adjacent rods are carefully set at fractions of the wavelength of the driving wave, so that the secondary waves interfere with the driving wave, amplifying it along the forward direction and reducing it along the sideways and backward directions.

Hofmann and his colleagues realized that gold nanorods should produce the same effect on the nanoscale - but here, the length-to-width ratio of the rods, rather than their length and spacing, is important.

The team etched their mini gold antenna into a glass substrate and drove it directly with red laser light.

The tricky part was to ensure that just one nanorod was driven by the incoming light, just as only one metal rod is in the Yugi-Uda antenna.

To ensure this, the team tilted the chosen nanorod by 45 degrees relative to its neighbours and stimulated it using laser light that was polarized at the same angle.

They then monitored the direction of light transmitted out of the glass substrate.

The result was actually better than their theory predicted, according to Hoffman, with roughly two-thirds of the input light being directed largely forwards. (ANI)

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Provdied by ANI
Souce: Sifynews (http://sify.com/news/nano-antennas-could-pave-way-for-quantum-computing-networks-news-international-kdpn4ddagfc.html)

(NanoRealm) - Could you imagine a laptop battery that lasted for 500 hours? How about an electric car that boasts a range many times that of a gasoline vehicle? For that matter, think about environmental sensors that could be scattered into the air like dust and collect data. While the last thing might not exactly be what you want for Christmas, a breakthrough in energy production made by MIT researchers could make such technology a reality during the next few years.

The process, dubbed “thermopower waves” by its discoverer, MIT’s Dr. Michael Strano, does nothing less than open up “a new area of energy research, which is rare,” says the scientist. MSNBC’s Michelle Bryner describes the phenomenon and its applications in brief, writing:

Researchers have found a way to produce large amounts of electricity from tiny cylinders made from carbon atoms.

The achievement could replace decades-old methods of generating electricity, such as combustion engines and turbines, the researchers say.

The cylinders are known as “carbon nanotubes,” which are, writes The Energy Collective, “submicroscopic hollow tubes made of a ‘chicken-wire-like’ lattice of carbon atoms.”

To describe the process in more detail, the MIT researchers took the nanotubes, applied a layer of fuel, and then ignited them at one end, creating a “fast-moving thermal [heat] wave traveling along the length of the carbon nanotube like a flame speeding along the length of a lit fuse,” explains the Environment News Service (ENS). This process is facilitated by the fact that nanotubes conduct heat far better than metals — up to 100 times faster. Then, getting more technical still, ENS writes, “As the heat feeds back to the fuel coating, a thermal wave is created that is guided along the nanotube. With a temperature of 3,000 kelvins [sic] (2,726 degrees Celsius or 4,940 degrees Fahrenheit) this ring of heat speads [sic] along the tube 10,000 times faster than the normal spread of this chemical reaction.”

This is where Dr. Strano and his team experienced their Ivory Soap moment. While Strano claims to be the first scientist to predict that thermal waves coursing through a nanotube could create electric current, the great amount of it yielded was not predicted by thermoelectric calculations. “Lo and behold,” said the scientist, “we were really surprised by the size of the resulting voltage peak.” Strano and his team have called this unexpected phenomenon “electron entrainment,” “since part of the current appears to scale with wave velocity,” said Strano.

Because this energy source is so new, it’s hard to predict what the practical applications will be. However, the thermopower-wave process produces 100 times the energy per unit of weight of the average lithium-ion battery. Additionally, Strano says that such a power source would be composed of non-toxic substances, eliminating the disposal problems posed by current-generation energy cells.

The technology could also be used to help create sensors the size of a grain of rice that could be injected into the body and used to monitor health (e.g., heart function), administer medical treatment or, well, use your imagination. There are some ominous implications as well.

One obvious use of the technology, however, would be to create practical electric fuel cells for automobiles. One common drawback of electric cars is that they typically have a very limited range relative to combustion engine vehicles, owing to the fact that gasoline contains far more energy per unit of weight than today’s electric fuel cells. But thermopower-wave generation could change that, providing light, long-range batteries and relatively inexpensive electricity. This could finally allow us to break our dependence on foreign oil.

Whatever the particulars, Dr. Strano’s discovery is just the latest frontier in the staggering field of nanotechnology. The science of manipulating matter on the molecular and even atomic levels, it is quickly making science fiction, science fact.

For more on the subject, see Selwyn Duke's “The New Nanotech World” in the March 31, 2008 issue of The New American.

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Provided by MIT
Source: http://www.thenewamerican.com/index.php/tech-mainmenu-30/energy/3133-nanotech-energy-source-discovered

(NanoRealm) - Researchers at MIT are working on getting computer chips to "self assemble" by coaxing molecules to arrange themselves into tiny but useful patterns, a process that could lead to microprocessors with much smaller circuit elements.

In the journal Nature Nanotechnology this week, the researchers describe a process that could become an alternative to conventional photolithography, which relies on light projected onto a photo-sensitive material, as people continue to forecast the demise of Moore's Law. That observation states that the number of transistors that can be placed on an integrated circuit doubles roughly every two years.
Led by Caroline Ross and Karl Berggren, both engineering professors, the scientists used electron beam lithography to create nanoscale "posts" on a silicon chip. They then deposited copolymers--large molecules of two polymers with repeating structural units--on the chip. The copolymers spontaneously linked to the posts and arranged themselves into useful patterns.
The polymers naturally want to separate from each other, thus causing them to arrange in predictable ways. (Berggren compares compares different polymer molecules to the characters played by Robert De Niro and Charles Grodin in "Midnight Run"--a bounty hunter and a white-collar criminal who are handcuffed together but can't stand each other.)
A variety of patterns that can be used in circuit design could be achieved by changing the shape and position of the posts, the proportions of the polymers, and the length of the molecule chains, MIT said.
When exposed to plasma, one polymer burns away, while the other turns to glass. The latter could work like a photoresist in optical lithography (a photoresist is a light-sensitive material onto which light is projected to form a pattern for the chip).
The team is still working to produce functioning circuits in a prototype chip, and to create even smaller chip features with the copolymer technique.

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Source: CNet (http://news.cnet.com/8301-17938_105-10468870-1.html)

(NanoRealm) - Consider this T-shirt: It can monitor your heart rate and breathing, analyze your sweat and even cool you off on a hot summer's day. What about a pillow that monitors your brain waves, or a solar-powered dress that can charge your ipod or MP4 player? This is not science fiction - this is cotton in 2010.

Now, the laboratory of Juan Hinestroza, assistant professor of Fiber Science and Apparel Design, has developed cotton threads that can conduct electric current as well as a metal wire can, yet remain light and comfortable enough to give a whole new meaning to multi-use garments. This technology works so well that simple knots in such specially treated thread can complete a circuit - and solar-powered dress with this technology literally woven into its fabric will be featured at the annual Cornell Design League Fashion Show on Saturday, March 13 at Cornell University's Barton Hall.

Using multidisciplinary nanotechnology developed at Cornell in collaboration with the universities at Bologna and Cagliari, Italy, Hinestroza and his colleagues developed a technique to permanently coat cotton fibers with electrically conductive nanoparticles. "We can definitively have sections of a traditional cotton fabric becoming conductive, hence a great myriad of applications can be achieved," Hinestroza said.
"The technology developed by us and our collaborators allows cotton to remain flexible, light and comfortable while being electronically conductive," Hinestroza said. "Previous technologies have achieved conductivity but the resulting fiber becomes rigid and heavy. Our new techniques make our yarns friendly to further processing such as weaving, sewing and knitting."
This technology is beyond the theory stage. Hinestroza's student, Abbey Liebman, was inspired by the technology enough to design a dress that actually uses flexible solar cells to power small electronics from a USB charger located in the waist. The charger can power a smartphone or an MP3 player.

"Instead of conventional wires, we are using our conductive cotton to transmit the electricity -- so our conductive yarns become part of the dress," Hinestroza said. "Cotton used to be called the 'fabric of our lives' but based on these results, we can now call it 'The fabric of our lights.'"

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Provided by Cornell University (http://www.cornell.edu/)
Source: http://www.physorg.com/news187372919.html

(NanoRealm) - Berkeley Lab researchers have found a better way to trap light in photovoltaic cells through the use of vertical arrays of silicon nanowires. This could substantially cut the costs of solar electric power by reducing the quantity and quality of silicon needed for efficient solar panels.

Solar cells made from silicon are projected to be a prominent factor in future renewable green energy equations, but so far the promise has far exceeded the reality. While there are now silicon photovoltaics that can convert sunlight into electricity at impressive 20 percent efficiencies, the cost of this solar power is prohibitive for large-scale use. Researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab), however, are developing a new approach that could substantially reduce these costs. The key to their success is a better way of trapping sunlight.



“Through the fabrication of thin films from ordered arrays of vertical silicon nanowires we’ve been able to increase the light-trapping in our solar cells by a factor of 73,” says chemist Peidong Yang, who led this research. “Since the fabrication technique behind this extraordinary light-trapping enhancement is a relatively simple and scalable aqueous chemistry process, we believe our approach represents an economically viable path toward high-efficiency, low-cost thin-film solar cells.”

Yang holds joint appointments with Berkeley Lab’s Materials Sciences Division, and the University of California Berkeley’s Chemistry Department. He is a leading authority on semiconductor nanowires - one-dimensional strips of materials whose width measures only one-thousandth that of a human hair but whose length may stretch several microns.

“Typical solar cells are made from very expensive ultrapure single crystal silicon wafers that require about 100 micrometers of thickness to absorb most of the solar light, whereas our radial geometry enables us to effectively trap light with nanowire arrays fabricated from silicon films that are only about eight micrometers thick,” he says. “Furthermore, our approach should in principle allow us to use metallurgical grade or “dirty” silicon rather than the ultrapure silicon crystals now required, which should cut costs even further.”

Yang has described this research in a paper published in the journal Nano Letters, which he co-authored with Erik Garnett, a chemist who was then a member of Yang’s research group. The paper is titled “Light Trapping in Silicon Nanowire Solar Cells.”

Generating Electricity from Sunlight

At the heart of all solar cells are two separate layers of material, one with an abundance of electrons that functions as a negative pole, and one with an abundance of electron holes (positively-charged energy spaces) that functions as a positive pole. When photons from the sun are absorbed, their energy is used to create electron-hole pairs, which are then separated at the interface between the two layers and collected as electricity.



Because of its superior photo-electronic properties, silicon remains the photovoltaic semiconductor of choice but rising demand has inflated the price of the raw material.

Furthermore, because of the high-level of crystal purification required, even the fabrication of the simplest silicon-based solar cell is a complex, energy-intensive and costly process.

Yang and his group are able to reduce both the quantity and the quality requirements for silicon by using vertical arrays of nanostructured radial p-n junctions rather than conventional planar p-n junctions. In a radial p-n junction, a layer of n-type silicon forms a shell around a p-type silicon nanowire core. As a result, photo-excited electrons and holes travel much shorter distances to electrodes, eliminating a charge-carrier bottleneck that often arises in a typical silicon solar cell. The radial geometry array also, as photocurrent and optical transmission measurements by Yang and Garrett revealed, greatly improves light trapping.

“Since each individual nanowire in the array has a p-n junction, each acts as an individual solar cell,” Yang says. “By adjusting the length of the nanowires in our arrays, we can increase their light-trapping path length.”

While the conversion efficiency of these solar nanowires was only about five to six percent, Yang says this efficiency was achieved with little effort put into surface passivation, antireflection, and other efficiency-increasing modifications.

“With further improvements, most importantly in surface passivation, we think it is possible to push the efficiency to above 10 percent,” Yang says.

Combining a 10 percent or better conversion efficiency with the greatly reduced quantities of starting silicon material and the ability to use metallurgical grade silicon, should make the use of silicon nanowires an attractive candidate for large-scale development.

As an added plus Yang says, “Our technique can be used in existing solar panel manufacturing processes.”

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Provided by: Provided by Lawrence Berkeley National Laboratory (http://www.lbl.gov/)
Source: http://www.physorg.com/news186850199.html

(NanoRealm) - Scientists in Manchester have found a clean and green way of making tiny magnets for high tech gadgets - using natural bacteria that have been around for millions of years.

The work by a team of geomicrobiologists from the University of Manchester paves the way for nanometer-size magnets - used in mobile phones and recording devices - to be made without the usual nasty chemicals and energy intensive methods.

Researchers studied iron-reducing bacteria that occur naturally in soils and sediments and found they can be used to create iron oxide nanoparticles with magnetic properties similar to those created through complex chemical processes.

Working with colleagues in Birmingham and Cardiff, the Manchester researchers also found a way of exercisising precise control over the size and magnetic strength of nanomagnets produced.
The high-tech particle accelerators at the Advanced Light Source at the famous Berkeley Labs near San Francisco, and the UK’s Diamond Light Source in Oxford at Harwell were used to verify findings.

Researchers added cobalt, manganese or nickel to the basic iron-based energy source used by bacteria, which resulted in the production of tiny magnets containing these elements. This greatly enhanced their useful magnetic properties.

Aside from being used in the latest gadgets, nanomagnets also have the potential to be used in drug delivery systems and cancer therapies to carefully focus and target the release of chemicals into the body.

Metal-reducing bacteria live in environments deficient in oxygen and react with oxidised metals to produce natural magnets in the ground beneath our feet.
And now the research team has developed a way of harnessing pure strains of these bacteria - which are in plentiful supply and reproduce quickly - to produce large quantities of nanomagnets at an ambient temperature.

This compares favourably to the extreme temperatures - as high as 1000 degrees Celsius - needed to create nanomagnets using current methods.
Prof Richard Patrick, Professor of Earth Science, said: “This is exciting work that raises the exciting prospect of a biologically friendly, energy-efficient method of producing nanomagnets tailored for different uses.”

A paper - ‘Harnessing the extracellular bacterial production of nanoscale cobalt ferrite with exploitable magnetic properties’ - outlining the research was published recently in the journal ACS Nano.

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(NanoRealm) - A team led by University of Wisconsin-Madison researchers has developed a new approach for creating powerful nanodevices, and their discoveries could pave the way for other researchers to begin more widespread development of these devices.

The discoveries were published in the online edition of Nature Materials (Feb. 28). Chang-Beom Eom, a UW-Madison professor of materials science and engineering, leads the team, which includes UW-Madison graduate students and research associates and collaborators from Penn State University, the University of Michigan and the University of California, Berkeley.

Particular metal-oxide materials (including some ferrites) have a unique magneto-electric property that allows the material to switch its magnetic field when its polarization is switched by an electric field and vice versa. This property means these materials can be used as bases for devices that act like signal translators capable of producing electrical, magnetic or even optical responses, and the devices can store information in any of these forms.

This could produce a variety of magnetoelectric devices with a wide range of applications, such as new integrated circuits or tiny electronic devices with the information storage capacity of hard drives.

"We all have electric and magnetic devices that run independently, but sometimes we want these functions integrated into one device with one signal used for multiple responses," says Eom.
Essentially, Eom and his team have developed a road map to help researchers "couple" a material's electric and magnetic mechanisms. As researchers run a current through a magnetoelectric device, electric signals follow the electric field like a path. The signals' ultimate destination could be, as an example, a memory "bank" operated by a magnetic field. When the researchers switch the electric field, the signals encounter a fork in the path. Though both prongs of the fork head in a similar direction, one path is the correct one and will prompt the magnetic field to switch. This will allow the information carried by the signals to be stored in the bank. If the signals take the incorrect path, the magnetic state won't switch, the bank remains inaccessible, and the information is lost as soon as the electric field turns off.

In addition to determining the proper path for the electric signals, the team has developed a matrix that ensures the cross-coupling effect is stable, or non-volatile, which allows for long-term data storage. This matrix is then embedded in thin films.

These two discoveries — the correct path and the stabilizing matrix — will allow other researchers to study the fundamental physics of cross-coupling in materials and begin investigating how to turn the many possibilities of multifunctional devices into reality.

"People have been imagining multiple uses for cross-coupling," says Eom. "This work will allow us to make nonvolatile magnetoelectric devices at the nanoscale, meaning we can store the information even after the power is turned off."

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More information: Journal: http://www.nature.com/nmat/index.html
Provided by University of Wisconsin-Madison (http://www.wisc.edu/)

Source from: http://www.physorg.com/news186670513.html

(NanoRealm) - Researchers at Tyndall National Institute in Cork, Ireland led by professor Jean-Pierre Colinge have reported in Nature Nanotechnology how they have designed and fabricated what is claimed to be the first junctionless transistor, which could significantly reduce power consumption and simplify the fabrication process for silicon chips, it is reckoned.

Existing transistors are based on junctions formed by adjacent layers of semiconductor material with different dopant-atom-induced polarities. Since controlling the junction allows current in the device to be turned on and off, it is the precise fabrication of this junction that determines the characteristics and quality of the transistor and is a major factor in production costs. However, as the distance between junctions drops below 10nm, extraordinarily high doping concentration gradients become necessary. Because of the laws of diffusion and the statistical nature of the distribution of the doping atoms, such junctions require increasingly complex and costly fabrication processes.

Tyndall’s new transistor consists of a silicon nanowire (about 30nm across just 10nm thick), and it has no junctions and no doping concentration gradients, since current flow is controlled by a ‘wedding ring’ gate structure around the wire. “These structures are easy to fabricate even on a miniature scale, which leads to the major breakthrough in potential cost reduction,” claims Colinge.

Another key challenge for the semiconductor industry is reducing the power consumption of complex transistors, with minimizing current leakage one of the main challenges. The new transistors — which can be made to have full CMOS functionality — have near-ideal subthreshold slope, extremely low leakage currents, and less degradation of mobility with gate voltage and temperature than classical transistors, Tyndall claims. “They have the potential of operating faster and using less energy than the conventional transistors used in today’s microprocessors,” says Colinge.

The junctionless transistor resembles the first ideal transistor structure, proposed in 1925, but to-date no-one had been able to fabricate it, continues Colinge. He attributes Tyndall’s junctionless transistor to the ability to fabricate a silicon nanowire with a diameter of just a few dozen atoms using electron-beam writing techniques and commercial silicon-on-insulator (SOI) wafers.

“We are beginning to talk about these results with some of the world’s leading semiconductor companies, and are receiving a lot of interest in further development and possible licensing of the technology,” says Tyndall’s CEO, professor Roger Whatmore.

The work was funded by Science Foundation Ireland, and is also underpinned by substantial investments in Tyndall by the Department of Enterprise Trade and Employment and the Higher Education Authority, comments Whatmore.

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Source: Semiconductor today - http://www.semiconductor-today.com/news_items/2010/MARCH/TYNDALL_010310.htm

Visit: www.nature.com

Visit: www.tyndall.ie/control

(NanoRealm) - Graphene, a one-atom-thick layer of a carbon lattice with a honeycomb structure, has great potential for use in radios, computers, phones and other electronic devices. But applications have been stymied because the semi-metallic graphene, which has a zero band gap, does not function effectively as a semiconductor to amplify or switch electronic signals.
 While cutting graphene sheets into nanoscale ribbons can open up a larger band gap and improve function, 'nanoribbon' devices often have limited driving currents, and practical devices would require the production of dense arrays of ordered nanoribbons — a process that so far has not been achieved or clearly conceptualized.

But Yu Huang, a professor of materials science and engineering at the UCLA Henry Samueli School of Engineering and Applied Science, and her research team, in collaboration with UCLA chemistry professor Xiangfeng Duan, may have found a new solution to the challenges of graphene.

In research to be published in the March issue of Nature Nanotechnology (currently available online), Huang's team reveals the creation of a new graphene nanostructure called graphene nanomesh, or GNM. The new structure is able to open up a band gap in a large sheet of graphene to create a highly uniform, continuous semiconducting thin film that may be processed using standard planar semiconductor processing methods.

"The nanomeshes are prepared by punching a high-density array of nanoscale holes into a single or a few layers of graphene using a self-assembled block copolymer thin film as the mask template," said Huang.

The nanomesh can have variable periodicities, defined as the distance between the centers of two neighboring nanoholes. Neck widths, the shortest distance between the edges of two neighboring holes, can be as low as 5 nanometers.

This ability to control nanomesh periodicity and neck width is very important for controlling electronic properties because charge transport properties are highly dependent on the width and the number of critical current pathways.

Using such nanomesh as the semiconducting channel, Huang and her team have demonstrated room-temperature transistors that can support currents nearly 100 times greater than individual graphene nanoribbon devices, but with a comparable on-off ratio. The on-off ratio is the ratio between the currents when a device is switched on or switched off. This usually reveals how effectively a transistor can be switched off and on.

The researchers have also shown that the on-off ratio can be tuned by varying the neck width.

"GNMs can address many of the critical challenges facing graphene, as well as bypass the most challenging assembly problems," Huang said. "In conjunction with recent advances in the growth of graphene over a large-area substrate, this concept has the potential to enable a uniform, continuous semiconducting nanomesh thin film that can be used to fabricate integrated devices and circuits with desired device size and driving current.

"The concept of the GNM therefore points to a clear pathway towards practical application of graphene as a semiconductor material for future electronics. The unique structural and electronic characteristics of the GNMs may also open up exciting opportunities in highly sensitive biosensors and a new generation of spintronics, from magnetic sensing to storage," she said.

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Source: PhysOrg.com: http://www.physorg.com/news186397884.html
Provided by University of California - Los Angeles: http://www.ucla.edu/
Nature Nanotechnology Paper Abstract: http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2010.8.html

(NanoRealm) - A tiny scaffold-like titanium structure of Nanonets coated with silicon particles could pave the way for faster, lighter and longer-lasting Lithium-ion batteries, according to a team of Boston College chemists who developed the new anode material using nanotechnology.

The web-like Nanonets developed in the lab of Assistant Professor of Chemistry Dunwei Wang offer a unique structural strength, more surface area and greater conductivity, which produced a charge/re-charge rate five to 10 times greater than typical Lithium-ion anode material, a common component in batteries for a range of consumer electronics, according to findings published in the current online edition of the American Chemical Society journal Nano Letters.

In addition, the Nanonets proved exceptionally durable, showing a negligible drop-off in capacity during charge and re-charge cycles. The researchers observed an average of 0.1% capacity fade per cycle between the 20th and the 100th cycles.

"As researchers pursue the next generation of re-chargeable Lithium-ion battery technology, a premium has been placed on increased power and a greater battery life span," said Wang. "In that context, the Nanonet device makes a giant leap toward those two goals and gives us a superior anode material."

Lithium-ion batteries are commonly used in consumer electronics devices. This type of rechargeable battery allows Lithium ions to move from the anode electrode to the cathode when in use. When charged, the ions move from cathode back to the anode.

The structure and conductivity of the Nanonets improved the ability to insert and extract Lithium ions from the particulate silicon coating, the team reported. Running at a charge/discharge rate of 8,400 milliamps per gram (mA/g) - which is approximately five to 10 times greater than similar devices - the specific capacity of the material was greater than 1,000 milliamps-hour per gram (mA-h/g). Typically, laptop Lithium-ion batteries are rated anywhere between 4,000 and 12,000 mA/h, meaning it would only take between four and 12 grams of the Nanonet anode material to achieve similar capacity.

Wang said the capability to preserve the crystalline titanium silicon core during the charge/discharge process was the key to achieving the high performance of the Nanonet anode material. Additional research in his lab will examine the performance of the Nanonet as a cathode material.

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News adapted from PhyOrg.com

More information: View the Nano Letters paper at http://pubs.acs.org/doi/abs/10.1021/nl903345f

Provided by Boston College (web)

(NanoRealm)- The world's first "power suit" seems closer to reality now. Scientists have come up with new fiber nanogenerators which may help design the very first one.

Researchers at University of California, Berkeley, developed the energy-scavenging nanofibers that can convert energy created through mechanical stress, stretches and twists into electricity, furthering hope of creating clothing that can power small electronics.

Liwei Lin, UC Berkeley professor of mechanical engineering and head of the international research team that developed the fiber nanogenerators, said: "This technology could eventually lead to wearable 'smart clothes' that can power hand-held electronics through ordinary body movements."

Lin, also co-director of the Berkeley Sensor and Actuator Center at UC Berkeley, added: "And because the nanofibers are so small, we could weave them right into clothes with no perceptible change in comfort for the user."

Chieh Chang, the study's lead author, who conducted the experiments while he was a graduate student in mechanical engineering at UC Berkeley, explained: "Surprisingly, the energy efficiency ratings of the nanofibers are much greater than the 0.5 to 4 percent achieved in typical power generators made from experimental piezoelectric PVDF thin films, and the 6.8 percent in nanogenerators made from zinc oxide fine wires."

Lin continued: "We think the efficiency likely could be raised further. For our preliminary results, we see a trend that the smaller the fiber we have, the better the energy efficiency. We don't know what the limit is."

Other co-authors of the study were Yiin-Kuen Fuh, a UC Berkeley graduate student in mechanical engineering; Van H. Tran, a graduate student at the Technische Universitat Munchen (Technical University of Munich) in Germany; and Junbo Wang, a researcher at the Institute of Electronics at the Chinese Academy of Sciences in Beijing, China.

The fiber nanogenerators were described in the Nano Letters, a peer-reviewed journal published by the American Chemical Society.

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Source-ANI

News from: MedIndia - (web)

In a just-published paper in the magazine Science, IBM (NYSE: IBM) researchers demonstrated a radio-frequency graphene transistor with the highest cut-off frequency achieved so far for any graphene device - 100 billion cycles/second (100 GigaHertz).


This accomplishment is a key milestone for the Carbon Electronics for RF Applications (CERA) program funded by DARPA, in an effort to develop next-generation communication devices.
The high frequency record was achieved using wafer-scale, epitaxially grown graphene using processing technology compatible to that used in advanced silicon device fabrication.

"A key advantage of graphene lies in the very high speeds in which electrons propagate, which is essential for achieving high-speed, high-performance next generation transistors," said Dr. T.C. Chen, vice president, Science and Technology, IBM Research. "The breakthrough we are announcing demonstrates clearly that graphene can be utilized to produce high performance devices and integrated circuits."

Graphene is a single atom-thick layer of carbon atoms bonded in a hexagonal honeycomb-like arrangement. This two-dimensional form of carbon has unique electrical, optical, mechanical and thermal properties and its technological applications are being explored intensely.
Uniform and high-quality graphene wafers were synthesized by thermal decomposition of a silicon carbide (SiC) substrate. The graphene transistor itself utilized a metal top-gate architecture and a novel gate insulator stack involving a polymer and a high dielectric constant oxide. The gate length was modest, 240 nanometers, leaving plenty of space for further optimization of its performance by scaling down the gate length.
It is noteworthy that the frequency performance of the graphene device already exceeds the cut-off frequency of state-of-the-art silicon transistors of the same gate length (~ 40 GigaHertz). Similar performance was obtained from devices based on graphene obtained from natural graphite, proving that high performance can be obtained from graphene of different origins. Previously, the team had demonstrated graphene transistors with a cut-off frequency of 26 GigaHertz using graphene flakes extracted from natural graphite.

Source: IBM (home;news)