Diamonds And Quantum Science

A diamond-based nanowire device. Researchers used a top-down nanofabrication technique to embed color centers into a variety of machined structures. By creating large device arrays rather than just "one-of-a-kind" designs, the realization of quantum networks and systems, which require the integration and manipulation of many devices in parallel, is more likely. Illustrated by Jay Penni.


Site of the day: http://nanotechweb.org/
Digging Deep Into Diamonds, Physicists Advance Quantum Science And Technology

By creating diamond-based nanowire devices, a team at Harvard has taken another step towards making applications based on quantum science and technology possible.

The new device offers a bright, stable source of single photons at room temperature, an essential element in making fast and secure computing with light practical.

The finding could lead to a new class of nanostructured diamond devices suitable for quantum communication and computing, as well as advance areas ranging from biological and chemical sensing to scientific imaging.

Published in the February 14th issue of Nature Nanotechnology, researchers led by Marko Loncar, Assistant Professor of Electrical Engineering at the Harvard School of Engineering and Applied Sciences (SEAS), found that the performance of a single photon source based on a light emitting defect (color center) in diamond could be improved by nanostructuring the diamond and embedding the defect within a diamond nanowire.

Scientists, in fact, first began exploiting the properties of natural diamonds after learning how to manipulate the electron spin, or intrinsic angular momentum, associated with the nitrogen vacancy (NV) color center of the gem. The quantum (qubit) state can be initialized and measured using light.

The color center "communicates" by emitting and absorbing photons. The flow of photons emitted from the color center provides a means to carry the resulting information, making the control, capture, and storage of photons essential for any kind of practical communication or computation. Gathering photons efficiently, however, is difficult since color-centers are embedded deep inside the diamond.

"This presents a major problem if you want to interface a color center and integrate it into real-world applications," explains Loncar. "What was missing was an interface that connects the nano-world of a color center with macro-world of optical fibers and lenses."

The diamond nanowire device offers a solution, providing a natural and efficient interface to probe an individual color center, making it brighter and increasing its sensitivity. The resulting enhanced optical properties increases photon collection by nearly a factor of ten relative to natural diamond devices.

"Our nanowire device can channel the photons that are emitted and direct them in a convenient way," says lead-author Tom Babinec, a graduate student at SEAS.

Further, the diamond nanowire is designed to overcome hurdles that have challenged other state-of-the-art systems—such as those based on fluorescent dye molecules, quantum dots, and carbon nanotubes—as the device can be readily replicated and integrated with a variety of nano-machined structures.

The researchers used a top-down nanofabrication technique to embed color centers into a variety of machined structures. By creating large device arrays rather than just "one-of-a-kind" designs, the realization of quantum networks and systems, which require the integration and manipulation of many devices in parallel, is more likely.

"We consider this an important step and enabling technology towards more practical optical systems based on this exciting material platform," says Loncar. "Starting with these synthetic, nanostructured diamond samples, we can start dreaming about the diamond-based devices and systems that could one day lead to applications in quantum science and technology as well as in sensing and imaging."

(http://www.physorg.com/news185372725.html)

Other articles:
http://www.popularmechanics.co.za/content/news/singlepage.asp?key=926
http://www.nature.com/nnano/journal/v5/n3/abs/nnano.2010.6.html

Junctionless transistor makes its debut

Site of the day: http://fooledbyrandomness.com/

Researchers in Ireland have succeeded in making the first junctionless transistor ever. The device, which resembles a structure first proposed way back in 1925 but not realized until now, has nearly "ideal" electrical properties, according to the team. It could potentially operate faster and use less power than any conventional transistor on the market today.

Transistors are the fundamental building blocks of modern electronic devices – and all existing transistors contain semiconductor junctions. The most common type of junction is the p–n junction, which is formed by the contact between a p-type piece of silicon – doped with impurities to create an excess of holes – and an n-type piece of silicon, doped to create an excess of electrons. Other junctions include the heterojunction, which is simply a p–n junction containing two different semiconductors, and the Schottky junction between metal and semiconductor.

The number of transistors on a single silicon microchip has been increasing exponentially since the early 1970s, and has gone up from a few hundred to over several billion today. As a result, transistors are becoming so tiny that it is becoming increasingly difficult to create high-quality junctions. In particular, it is very difficult to change the doping concentration of a material over distances shorter than about 10 nm. Junctionless transistors could therefore help chipmakers continue to make smaller and smaller devices.
Patented in 1925

Now, Jean-Pierre Colinge and colleagues at the Tyndall National Institute of University College Cork have dispensed with the very idea of a junction and instead have turned to a concept first proposed in 1925 by Austrian-Hungarian physicist Julius Edgar Lilienfield. Patented under the title "Device for controlling electric current", it is a simple resistor and contains a gate that controls the density of electrons and holes, and thus current flow.

The team's version of the device consists of a silicon nanowire in which current flow is perfectly controlled by a silicon gate that is separated from the nanowire by a thin insulating layer. The structure itself is very simple, looking a bit like a telephone cable that is fixed to a surface by a plastic clip (see figure). Crucially, there is no need to alter the doping over very short distances. Instead, the entire silicon nanowire is heavily n-doped, making it an excellent conductor. However, the gate is p-doped and its presence has the effect of depleting the number of electrons in the region of the nanowire under the gate.

If a voltage is simply applied along the nanowire, current cannot flow through this depleted region. According to Colinge, this region "squeezes" the current in the nanowire in the same way as the flow of water in a hose is stopped by squeezing it. However, if a voltage is applied to the gate, the squeezing effect is reduced and current can flow. The team also made a similar device with a p-type nanowire and n-type gate.
The most perfect of transistors

The structure is simple to build, even at the nanoscale, which means reduced costs compared with conventional junction fabrication technologies, which are becoming more and more complex. The device also has near-ideal electrical properties, adds Colinge, and behaves like the most perfect of transistors. This means that it hardly suffers at all from current leakage – the bane of conventional devices – and so could potentially operate faster and using less energy.

The Tyndall team says that it is now talking to some of the world's leading semiconductor companies to further develop and possibly license its technology.

"Although the idea of a transistor without junctions may seem quite unorthodox, the word "transistor" does not imply the presence of junctions, per se," write the researchers in Nature Nanotechnology, where the work was published. "A transistor is a solid-state device that controls current flow and the word transistor is a contraction of 'trans- resistor'."


(http://physicsworld.com/cws/article/news/41881)

Bloom Energy unveils fuel cell of the future

Site of the day: http://fooledbyrandomness.com/

A man stands next to a Bloom Energy server called a "Bloom Box" during a product launch at the eBay headquarters in San Jose, California. Bloom Energy, a Silicon Valley start up, introduced the "Bloom Box", a solid oxide fuel cell server that can generate electricity at a cost of 8 to 10 cents per kilowatt hour using natural gas.

Stealth start-up Bloom Energy on Wednesday publicly unveiled an innovative fuel cell that promises to deliver affordable, clean energy to even remote corners of the world.

Compact Bloom Servers built with energy cells made from silicon -- a plentiful element found in sand -- made their formal debut in an eBay building here partially powered by the energy source.

"Bloom fuel cell technology has the potential to revolutionize the energy industry," California governor Arnold Schwarzenegger said while introducing Bloom founder K.R. Sridhar.

"He is someone shaping the future of energy not just for California but for the world," Schwarzenegger said.

A high-powered audience gathered for the invitation-only event included Google co-founder Larry Page, eBay chief executive John Donahoe, and former US secretaries of state George Shultz and Colin Powell.

"The core of our technology simply is sand," Sridhar said pulling a black cloth off a clear glass container of sand and then holding up a greeting-card sized cell made from the material.

"It is available in plenty... and it has the scientific property that enabled us to make a fuel cell," he said.

Fuel cell technology dates back to the mid 1800s, but Bloom found a way to eliminate the need for expensive metals such as platinum and to generate electricity by pushing around oxygen molecules.

Bloom servers work with a variety of fuels, meaning users can freely switch to whatever is locally available or most affordable, according to Sridhar.

The servers, referred to by some as "Bloom boxes" despite Sridhar cringing at the nickname, have been secretly tested in California by a group of major corporations including eBay, Wal-Mart, and Coca Cola.

Google was Bloom's first customer, buying four servers that it installed at its campus in Mountain View, California.

"I'm a big supporter of this," Page said during an on-stage chat with renowned Silicon Valley venture capitalist John Doerr of Kleiner Perkins Caulfield & Byers, a major backer of Bloom.

"I'd love to see us have a whole data center running on this at some point when they are ready," Page said.

Bloom servers capable of pumping out 100 kilowatts of electricity each cost 700,000 to 800,000 dollars but the price is expected to plummet as production ramps up and efficiencies of scale are achieved.

Sridhar predicted it will take about a decade for the technology to get to the point where it can be used in homes.

Bloom servers are 60 percent cleaner than coal-fired power plants and produce reliable energy on-site instead of having electricity routed through wires from far-off generation plants, Schwarzenegger said.

The inspiration for the fuel cell is rooted in Sridhar's decade as a university professor working on ways to sustain a human colony on Mars.

"I was trying to make Mars our second home," Sridhar said. "The technology was robust but, unfortunately, I couldn't say the same thing about the funding and the rockets."

Sridhar focused his inventive energy on Earth's need to curb pollution and sate growing energy demands. "If we continued the way we were going we would be handing our children a broken planet," he said.

The cells are described as being twice as efficient as the US electricity grid, meaning it takes half the fuel to produce the same amount of energy.

Sridhar hefted a brick-sized fuel cell in one hand, saying it could power a standard light bulb but will soon be able to satisfy the electricity needs of a typical US home.

"In a few years we will use it to make a home energy server of the future," Sridhar said.

Sridhar pulled back a curtain to reveal a set of Bloom Servers -- refrigerator-sized metal boxes housing stacks of fuel cells.

"That's my baby," he said. "Isn't she beautiful."

Electricity generated by Bloom servers costs about nine cents per kilowatt/hour as opposed to the 14 or 15 cents typically charged here by utilities.

The cost of the servers is recovered in three to five years by energy savings, according to Sridhar. The servers are guaranteed for 10 years. Sridhar would not disclose the lifespans of the fuel cells.

"We sent our chief financial officer to make sure this thing penciled out," Donahoe said of eBay's decision to try Bloom technology. "It is something that makes good green sense making good business sense."

Former secretary of state Colin Powell, a Bloom board member and retired general, said the servers could be a boon to the military, which has grown increasingly energy-dependent as technology infuses the tools of war.

"This is a breakthrough," Powell said. "Sooner or later it is going to be in homes all across America. Think what it will ultimately do for humankind."

(http://www.physorg.com/news186246027.html)

Other articles:
http://www.physorg.com/news186123245.html
http://www.technologyreview.com/energy/24650/

Energy-Efficient Lighting Made Without Mercury

Site of the day: http://fooledbyrandomness.com/

ScienceDaily (Feb. 15, 2010) — RTI International has developed a revolutionary lighting technology that is more energy efficient than the common incandescent light bulb and does not contain mercury, making it environmentally safer than the compact fluorescent light (CFL) bulb.

At the core of RTI's breakthrough is an advanced nanofiber structure that provides exceptional lighting management. Nanofibers are materials with diameters and surface features much smaller than the human hair but with comparable lengths.

RTI's technology, which was funded in part by the Department of Energy's Solid-State Lighting program, centers around advancements in the nanoscale properties of materials to create high-performance, nanofiber-based reflectors and photoluminescent nanofibers (PLN). When the two nanoscale technologies are combined, a high-efficiency lighting device is produced that is capable of generating in excess of 55 lumens of light output per electrical watt consumed. This efficiency is more than five times greater than that of traditional incandescent bulbs.

"By using flexible photoluminescent nanofiber technologies for light management, RTI has opened the door to the creation of new designs for solid-state lighting applications," says Lynn Davis, Ph.D., director of RTI's Nanoscale Materials Program. "This new class of materials can provide cost-effective, safe and efficient lighting solutions."

Additionally, RTI's technology produces an aesthetically pleasing light with better color rendering properties than is typically found in CFLs. The technology has demonstrated color rendering indices in excess of 90 for warm white, neutral white, and cool white illumination sources.

"Because lighting consumes almost one-fourth of all electricity generated in the United States, our technology could have a significant impact in reducing energy consumption and carbon dioxide emissions," Davis said. "The technology also does not contain mercury, which makes it more environmentally friendly and safer to handle than CFLs and other fluorescent lamps."

RTI is continuing development of this technology and is actively pursuing commercialization opportunities in the marketplace. It is anticipated that commercial products containing this breakthrough will be available in three to five years.

(http://www.sciencedaily.com/releases/2010/02/100211140629.htm)

New Energy Source from the Common Pea: Scientists Create a Solar Energy Device from a Plant Protein Structure

Site of the day: http://fooledbyrandomness.com/

ScienceDaily (Mar. 4, 2010) — If harnessing the unlimited solar power of the sun were easy, we wouldn't still have the greenhouse gas problem that results from the use of fossil fuel. And while solar energy systems work moderately well in hot desert climates, they are still inefficient and contribute only a small percentage of the general energy demand. A new solution may be coming from an unexpected source -- a source that may be on your dinner plate tonight.

"Looking at the most complicated membrane structure found in a plant, we deciphered a complex membrane protein structure which is the core of our new proposed model for developing 'green' energy," says structural biologist Prof. Nathan Nelson of Tel Aviv University's Department of Biochemistry. Isolating the minute crystals of the PSI super complex from the pea plant, Prof. Nelson suggests these crystals can be illuminated and used as small battery chargers or form the core of more efficient artificial solar cells.

Nanoscience is the science of small particles of materials and is one of the most important research frontiers in modern technology. In nature, positioning of molecules with sub-nanometer precision is routine, and crucial to the operation of biological complexes such as photosynthetic complexes. Prof. Nelson's research concentrates on this aspect.

The mighty PSI

To generate useful energy, plants have evolved very sophisticated "nano-machinery" which operates with light as its energy source and gives a perfect quantum yield of 100%. Called the Photosystem I (PSI) complex, this complex was isolated from pea leaves, crystalized and its crystal structure determined by Prof. Nelson to high resolution, which enabled him to describe in detail its intricate structure.

"My research aims to come close to achieving the energy production that plants can obtain when converting sun to sugars in their green leaves," explains Prof. Nelson.

Described in 1905 by Albert Einstein, quantum physics and photons explained the basic principles of how light energy works. Once light is absorbed in plant leaves, it energizes an electron which is subsequently used to support a biochemical reaction, like sugar production.

"If we could come even close to how plants are manufacturing their sugar energy, we'd have a breakthrough. It's therefore important to solve the structure of this nano-machine to understand its function," says Prof. Nelson, whose lab is laying the foundations for this possibility.

Since the PSI reaction center is a pigment-protein complex responsible for the photosynthetic conversion of light energy to another form of energy like chemical energy, these reaction centers, thousands of which are precisely packed in the crystals, may be used to convert light energy to electricity and serve as electronic components in a variety of different devices.

"One can imagine our amazement and joy when, upon illumination of those crystals placed on gold covered plates, we were able to generate a voltage of 10 volts. This won't solve our world's energy problem, but this could be assembled in power switches for low-power solar needs, for example," he concludes.

(http://www.sciencedaily.com/releases/2010/03/100304112237.htm)

Wireless Power Transmission

Site of the day: http://www.wired.com/

Invisible Power

Marin Soljacic couldn't sleep. The problem was his wife's Nokia cell phone. The tyrannical device beeped on the bedside table when it needed to be plugged in. It could not be disabled.

Instead of taking a hammer to the phone, Soljacic marveled at the fact that this device, and billions of others like it, was sitting a few feet away from all the electricity it could ever need. Why couldn't it receive power wirelessly, just as laptops get Wi-Fi?

Being a physics professor, not an electrical engineer, Soljacic didn't know the history of failed attempts to produce wireless electricity. (Thomas Edison and his rival Nikola Tesla were among the first to envision long-distance power-beaming.) Soljacic also didn't pause to consider conduction, the kind of close-range charging used in electric toothbrushes, which is about as far as wireless electricity got before him.

Soljacic learned that if you could get two magnetic fields to resonate -- to sing the same note, in effect -- they could transfer an electric current. With two large magnetic coils, he found in an experiment described in Science magazine in 2007, you can throw 60 watts across a room, powering a lightbulb. (Keeping the two resonators in perfect harmony over a distance is not simple; Soljacic spent several years running lab experiments before he built a system that worked reliably.)

MIT, his employer, quickly patented the technology (Soljacic's name is on the patent) and encouraged Soljacic to start a company. He would sit on the board but find executives to run it full time. The result can be found on the second floor of a brick building in Cambridge, Mass. leased to the company by the big-and-tall tailor on the ground level.

WiTricity's 15 employees are hard at work proving that Soljacic's magnetic coils can power almost any electrical device. David Schatz, director of business development, shows me a TV, a DVD player and a computer, all of them wireless.

"This was our No. 1 request from business users," Schatz says, switching on a projector. "Look: no batteries, no wires, nothing up my sleeve." The coil sending out the power is hidden behind an abstract painting that the CEO's wife rescued from their basement.

Schatz is the first to admit that the housing they've hurriedly built for the receiving coils is too bulky. "No one would want to buy this," he says, pointing to the pack that juts out from the back of the laptop, a pregnant plastic bulge that's about a third as large as the device itself.

Given sufficient cooperation from equipment manufacturers, WiTricity is confident that it can incorporate its coil into the guts of any device. (Think of how computermakers like Apple (AAPL, Fortune 500) turned bulky Webcams into fingernail-size lenses that fit in a thin laptop case.) CEO Eric Giler, a veteran tech executive who ran a telecom company for 22 years, understands the importance of letting potential partners play with patented technology.

So far about a dozen companies -- including Intel (INTC, Fortune 500) and Sony (SNE) -- have tried replicating Soljacic's groundbreaking MIT experiment in their own research facilities, just to make sure it's the real deal. That might make other CEOs nervous, but not Giler.

"Our best customers are going to be the guys who try to do this," he says, "because it is really hard." The company is also talking to furniture manufacturers about fitting coils into desks and cubicle walls. The first announcement of a WiTricity partner product is expected toward the end of 2010.

Most of Giler's potential customers have one major question: safety. "There's a real perceptual problem," he says. "People think we're putting electricity in the air, and that's called lightning, and they know to stay away from that."

In fact, the coils turn electricity into magnetic fields, then back into electricity. And as any physicist will tell you, magnetic fields interact weakly with humans; as far as the fields are concerned, we are no different from air. (The Earth itself exudes a magnetic field.)

Initially, Giler was skeptical. Magnetism from MRI machines can disable pacemakers. Wouldn't wireless electricity pose similar risks? Soljacic replied that MRI magnetism is about 10,000 times stronger than his version. The Institute of Physics in London concurs: WiTricity's magnetic field "has no detrimental effects on the human body."

Giler makes a point of standing between the coils whenever he demonstrates the technology. At the Nikkei electronics conference in Tokyo in October, he was able to power a 1,000-watt klieg light from across the room -- a far cry from that 60-watt lightbulb in Soljacic's first experiment. "We're going up the power curve," he says.

WiTricity's record so far is 3,000 watts -- enough to fully charge an electric car, so long as it's in the same room (or garage). How big could WiTricity get? "Every single person in the world can relate to the problem of running out of batteries or having wires everywhere," Giler says. "The market is so potentially huge that numbers become meaningless."

A wireless electric world could free up designers to create entirely new kinds of products, no longer hemmed in by the need for boxy batteries or power supplies. As one of Giler's VC investors says, "I bet you that's your bestseller in five years' time. You don't even know what it is yet."

By Chris Taylor

(http://money.cnn.com/2009/11/24/smallbusiness/next_little_thing_2010.fsb/index3.htm)

More articles:
http://gizmodo.com/5471431/mit-wireless-power-discovery-proves-two-is-better-than-one
http://www.newscientist.com/article/dn18521-more-is-merrier-for-wireless-power-supply.html

Nanoprinter could have cells lining up to be tested

Site of the day: http://openwetware.org/

BORROWING a trick from the office photocopier may make it possible for a nanoscale printer to precisely manipulate biological cells for use in artificial tissue.

In 2007, John Rogers at the University of Illinois at Urbana-Champaign and colleagues produced a printer small enough to print electronic circuits from conductive ink on the nanoscale. By modifying the technique, they think it should be possible to manipulate biological cells or biomolecules such as DNA, says Rogers.

The team's electrohydrodynamic jet (e-jet) printer works by establishing a voltage difference between its metallic nozzle and a substrate below. The resulting electric fields cause charged ions in the ink to congregate in a meniscus at the nozzle. Because the charged ions repel one another, the meniscus deforms into the shape of a cone, creating an ultra-fine tip from which tiny ink droplets are shed.

This process produces an imbalance in the quantities of positive and negative ions in the printed ink, and the team realised that by switching the polarity of the voltage, they could print intricate patterns of positive or negative charge onto the substrate (Nano Letters, DOI: 10.1021/nl903495f).

Once a pattern of charge is printed onto a substrate, the static could attract charged molecules and cells, marshalling them into shape in the same way toner inside a photocopier is forced into the required design. "[But] xerography itself does not offer comparable resolution," says Rogers.

The technique could complement cell-printing techniques for artificial tissue manufacture by helping to guide cells too fragile to be printed into position inside a 3D matrix. "It could be very useful indirect manipulation of cells," says Vladimir Mironov, a biofabrication researcher at the Medical University of South Carolina in Charleston.

(http://www.newscientist.com/article/mg20527455.700-nanoprinter-could-have-cells-lining-up-to-be-tested.html)