Normally, a glass window doesn’t care where a ray of light came from. But special kinds of glass or plastic could be a bit pickier.

Nonlinear materials could distinguish between two rays of light coming from opposite directions, say two Italian physicists. Blocking a ray from one direction and allowing in a ray from the other could be useful for making a one-way street for light.

Textbook optics prohibits this kind of directional discrimination. Everyday linear materials are governed by the reciprocity theorem, which says that a beam of light coming from the left will pass through and reflect off a material in the same way as a beam of light coming from the right.
But nonlinear materials, which can change as light passes through them, play by different rules.

“Without nonlinearity this asymmetry would not be possible,” says Giulio Casati, a physicist at the University of Insubria in Como, Italy.

A textbook pendulum, for instance, swings with a steady frequency that can be calculated from equations. But a nonlinear pendulum’s frequency changes over time in a way that can be worked out only with a computer.

Casati mathematically modeled the behavior of light passing through two layers of nonlinear material. The light changes the properties of the materials as it passes through, which in turn changes the behavior of light in complex ways.

Thanks to this back-and-forth dance, the frequency of light that can pass through these materials depends on the direction of the light, he reports in the April 22 Physical Review Letters.
“Other people have used nonlinearity, but they use it in a different way,” says Panayotis Kevrekidis, a mathematical physicist at the University of Massachusetts Amherst who wasn’t involved in the research.
Previous attempts to break down the reversibility of light used photonic crystals. Those materials can only block a portion of the light that has been boosted to twice its original frequency.
Casati’s initial simulations describe a way to transmit about 80 percent of the light traveling in one direction while blocking about 70 percent of the light coming from the opposite direction.
This selectivity could be useful for making wave diodes. Just as a traditional diode allows electrical current to flow only one direction in a piece of electronics, a wave diode could guide the flow of light in quantum or optical computing.

“This simple model may also apply to more general situations, like acoustics or different kinds of waves,” says Stefano Lepri, a physicist at the Italian National Research Council Institute for Complex Systems in Florence and a coauthor of the study. Materials that respond to sound waves nonlinearly could, he suggests, be useful for one-directional soundproofing.

Image: A proposed wave diode would allow light coming from the left to pass through (image on left) but reflect light coming from the other direction (right). (Stefano Lepri/Physical Review Letters)

• By Devin Powell, Science News
• April 20, 2011

Slimy mats of bacteria called biofilms may be the most liquid-repellent materials in nature, researchers have discovered.

“There are a few man-made materials that can perform better, and they have to be made in clean rooms. They’re incredibly expensive and brittle,” said materials scientist Alexander Epstein of Harvard University, co-author of the new study. “Making biofilm is as easy as growing bacteria.”
The goo secreted by Bacillus subtilis bacteria not only deflects water like a lotus leaf, but also repels concentrated alcohol, acetone and even vaporized liquid, according to a study published Jan. 18 in Proceedings of the National Academy of Sciences.

Biofilms are communities of bacteria that stick together using a mixture of sugars and proteins called the extracellular matrix, which takes on a wrinkled form under powerful microscopes (see image below). Since the discovery of bacteria in the late 1600s, most research has covered individual cells. It’s only since the 1990s that scientists have begun to understand the pervasiveness and importance of biofilms.

“We’re realizing more and more that almost all bacteria in nature are found as biofilms,” Epstein said. “It offers a lot of advantages for them, including better protection and increased chances they’ll stick to sources of food. It’s crazy stuff.”

While trying to map the internal structure of B. subtilis biofilm using a vaporized radioactive tracer that would show up in x-ray photos, the researchers found it couldn’t get inside. They were frustrated at first, but Epstein said his team soon realized the significance of the stubborn biofilm.
“We started to put different liquids on it. Concentrated alcohols just [beaded up],” Epstein said. For comparison, the researchers also tried a non-stick Teflon surface. “We found the biofilms substantially superior to Teflon,” he said.

To analyze resistance to wetting, Epstein and his team measured the angle between droplets of liquid and the materials’ surfaces (right). At 10 percent alcohol, similar to wine’s concentration, Teflon started getting wet. Biofilms, however, balled up all concentrations of alcohol up to 80 percent (similar to Everclear). Liquids wetted biofilms only after sitting on them for minutes or hours.
Epstein isn’t suggesting we grow biofilms for frying pans or rain jackets, but thinks the research will inspire practical new applications. His team ultimately hopes to resolve biofilm’s molecular structure to develop new materials.
“We don’t fully understand it, but it’s broadly true that you need both protein and sugars for this repelling property,” Epstein wrote in an e-mail to Wired.com. “Sugars absolutely have to be there, but we don’t know why. We’re doing some followup research on that now,” he said.

Images: Courtesy of PNAS/Alexander Epstein et al. 1) A bead of 50 percent ethanol rests on a biolfilm of B. subtilis bacteria sliced from a Petri dish. 2) Wetness of a surface is determined by the contact angle of liquid droplets, and increases sharply when a droplet’s inner contact angle is less than 90 degrees. 3) A scanning electron micrograph of a mutant B. subtilis strain’s extracellular matrix, or ECM.

• By Dave Mosher
• January 31, 2011

An Australian university constructed graphene paper by milling graphite, and for the first time it was malleable, 10 times stronger than steel, 6 times lighter, and more rigid at the same time.

A UTS (University of Technology, Sydney) research team recently created strong graphene paper from graphite with a tensile strength ten times greater than that of steel. It is also six times lighter, two times harder, and exhibited thirteen times more resistance to bending than steel, and of course, it does not rust.

Graphene is a material consisting of carbon nanotubes which has very unique property combinations which composite materials do not, such as malleability, exceptional thermal and electrical conductivity, high strength, the ability to be rigid as well, very light weight, and the material required to construct it is not rare. Nothing on the planet has ever even come remotely close to these exceptional characteristic combinations.

The lead researcher Ali Reza Ranjbartoreh said: “No one else has used a similar production and heat testing method to find and carry out such exceptional mechanical properties for graphene paper. We are definitely well ahead of other research societies.”

Ali Reza Ranjbartoreh also added: “The exceptional mechanical properties of synthesised GP render it a promising material for commercial and engineering applications. Not only is it lighter, stronger, harder and more flexible than steel it is also a recyclable and sustainable manufacturable product that is eco-friendly and cost effective in its use.”

There are many implications of such a technological advancement. If affordable, it can:

• Make significantly stronger, very efficient, more environmentally sound, and lighter vehicles, from economy cars, to trains, buses, ships, and passenger jets.
• Extend the range and performance of electric vehicles due to its light weight, and reduce the required battery capacity due to less weight, because less weight requires less power, and power is provided by the batteries.
• Make much stronger, lighter, and more efficient wind turbine blade designs possible. Blades could bend instead of break. It would be able to prevent damage to wind turbine blades caused by lightning strikes. Wind turbine blades are normally constructed with composite non-metals which do not conduct electricity well and therefore cannot safely channel lightning into the ground. When lightning strikes a composite wind turbine blade, the temperature of the air inside it can increase 30,000 degrees Celsius, causing it to expand rapidly (explode). The blades are equipped with lightning receptors at the tip which channel the current into the ground, and this is helpful, but not always enough. Like lightning rods, wind turbines need to be designed so that they attract lightning to conductive materials such as metals that channel them into the ground. In other words, they divert them into the ground so they don’t reach sensitive components, because electricity follows the path of least resistance.
• All portable devices such as notebook computers, tablet PCs, cellphones, music players, could be stronger while still being lightweight.

Another key advantage of this material is that it is recyclable.
Australian mines happen to contain a large amount of graphite, meaning that the widespread use of such a material in the future could be very beneficial to Australia. This industry is likely to grow in the foreseeable future as it strides up a long path to becoming mainstream.

Mr Ranjbartoreh said that the results of this project promise significant benefits to the use of this material in the aviation and automotive industries.

Physorg
Images via University of Technology Sydney

Nano-cones could help neutralize manufacturing defects in solar cells

A new advance in solar cells that tips the surface with minuscule cone structures could neutralize manufacturing defects, boosting efficiency up to 80 percent.

In conventional solar panels, more than 50 percent of the charges generated by sunlight are lost due to defects, said Jun Xu, a researcher at the Department of Energy's Oak Ridge National Laboratory. The irregularities in the formation of the crystalline structure of solar cells can trap electrons and limit the transfer of sunlight to electrical energy.


 SOLAR FLAWS: Manufacturing defects impair solar cells ability to turn sunlight into electricity, but a new technique might help minimize the flaws. Image: Stephan Kambor via Wikimedia Commons

This is why Xu and his team are looking at how nanocones -- cone-shaped structures one-millionth of a meter long -- can neutralize the burden of defects.

The negative-polarity nanocones are made of zinc oxide, and surrounded by a positive-polarity cadmium telluride semiconductor that absorbs sunlight. The three-dimensional cone structure acts as a junction between the zinc oxide and cadmium telluride, making for a smoother conversion of the solar charge to electricity.

The idea, said Xu, is not to "fix" the defects, but to make them irrelevant. With the nanocone structure, the team was able to increase the overall electric charge to overcome the pitfalls of defects.
"If [manufacturers] make a defect with no way to solve it, we make the defect less relevant," he said. "You need to increase the efficiency ... you need to be able to increase change of transport. With a nanocone structure, you can do that."

On a small level, the efficiency gains are relatively minor -- rising to 3.2 percent, compared to 1.8 percent for panels without the nanocones. But Xu believes this will pay off on a larger scale.
"Our efficiency is moderate in generation, but the difference between the two platforms is huge," he said, referring to the models with and without nanocones. In the real world, even a much smaller percentage increase would be an important achievement for solar.

"If we can reduce the defective material, and we can increase the efficiency about 15 or 10 percent," he said, "that would be a huge success."

Zinc oxide and cadmium telluride serve as relatively cheap materials to create nanocones, as well, said Xu, with the potential to reduce the cost of commercial solar panels if applied to silicon -- the most common material used for solar panels.

The research will be published in the Institute of Electrical and Electronics Engineers' IEEE Proceedings.

From Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

Experimental networked display refreshes holograms every two seconds

An image of an F4 Phantom fighter jet created with the new 3D telepresence system.
Researchers at the University of Arizona (UA), Tucson, have developed a holographic system that can transmit a series of 3D images in near-real-time, a precursor to holographic videoconferencing.

The system incorporates a novel, photorefractive polymer--one that can rapidly refresh holographic images and is scalable for production--coupled to a unique system for recording and transmitting 3D images of individuals and objects via Ethernet.

Lead author Pierre-Alexandre Blanche and his colleagues from the university and Nitto Denko Technical Corp. of Oceanside, Calif., describe the breakthrough in the cover story of the Nov. 4, 2010, issue of Nature.

"This advance brings us a step closer to the ultimate goal of realistic holographic telepresence with high-resolution, full-color, human-size, 3D images that can be sent at video refresh rates from one part of the world to the other," says co-author and project lead Nasser Peyghambarian of UA and the Director of NSF's multi-institution Engineering Research Center for Integrated Access Networks (CIAN).

The researchers had previously demonstrated a refreshable polymer display system, but it could refresh images only once every four minutes. The new system can refresh images every two seconds; while not yet ideal for a display, the rate is more than one hundred times faster.

Additionally, using a single-laser system for writing the images onto the photorefractive polymer, the researchers can display visuals in color. While the current refresh rate for multi-color display is even slower than for monochromatic images, the development suggests a true 3D, multicolor system may be feasible.
"This breakthrough opens new opportunities for optics as a means to transport images in real time," says Lynn Preston, director of the NSF Engineering Research Centers program that supports CIAN. "Such a system can have an important impact on telepresence, telemedicine, engineering design and manufacturing, and other applications. This is an early and tremendously important outcome from this three-year old center."
More information is available in the UA press release.



Project lead Nasser Peyghambarian of the University of Arizona, who is also director of NSF's multi-institution Engineering Research Center for Integrated Access Networks (CIAN), explains the technology--a holographic system that can transmit a series of 3D images in near-real-time, a precursor to holographic videoconferencing.

Credit: National Science Foundation



A hologram of a member of Peyghambarian's lab appears in the photorefractive polymer screen. Moving the camera from side to side reveals what the researchers call parallax, one of the novelties of this research: The holographic image presents itself from different perspectives as the viewer moves his or her head from side to side or up and down.

Credit: N. Peyghambarian, University of Arizona 



This holographic representation of a vase shows different colors capable with the new system and an effect known as parallax, which makes the image life-like: As the viewer moves his or her head from side to side or up and down, the holographic image presents itself from different perspectives.

Credit: N. Peyghambarian, University of Arizona 



A pulsed 50-Hz Laser inscribes a holographic image of a F-4 fighter jet into the photo-refractive polymer screen.

Credit: N. Peyghambarian, University of Arizona



A laser inscribes a series of holograms into the photorefractive polymer screen. Each iteration of the writing process takes only two seconds.

Credit: N. Peyghambarian, University of Arizona


Study co-author and project lead Nasser Peyghambarian of the University of Arizona, Tucson, the director of NSF's multi-institution Engineering Research Center for Integrated Access Networks (CIAN).

Credit: University of Arizona

Team member Vivian Sieh holds up the photorefractive polymer that has enabled the new 3D telepresence system to achieve a two-second refresh rate.

Credit: University of Arizona 

This material is based upon work supported by the Engineering Research Center Program of the National Science Foundation under NSF Cooperative Support Agreement Award No. EEC-0812072
 
-NSF-
November 3, 2010
Press Release 10-207

A new battery demonstrated a power output 10 times higher, for its size, than what is expected of a conventional rechargeable lithium battery.
Imagine that the same rechargeable battery in your cell phone could power a device that requires 10 times the energy. That possibility may be closer than you think.

A battery created by researchers at Massachusetts Institute of Technology demonstrated an increased capacity for charge by roughly a third and a power output 10 times higher, for its size, than what is expected of a conventional rechargeable lithium battery. The results were published yesterday in Nature Nanotechnology.

The research team, led by Yang Shao-Horn, an associate professor of materials science and mechanical engineering, and Paula Hammond, professor of chemical engineering at MIT, achieved this by creating an entirely new kind of electrode -- in this case, by modifying the positive end of the conventional battery, which is called the cathode.

The collaboration began through graduate student Seung Woo Lee, studying fuel cells, who was advised by both Shao-Horn and Hammond. Lee defended his doctoral dissertation this spring.

Using commercially available carbon nanotubes -- hollow cylinders 50,000 times thinner than a human hair but composed of carbon atoms -- the team fabricated the cathode entirely out of the nanotubes put down in layers.

The large surface area of a nanotube allows it to store more charge than other types of carbon, such as graphite, but previous battery fabrication methods tended to obscure these surfaces.

Using the exposed surfaces allows more charge to be stored -- increasing capacity -- while also letting those charges migrate more easily -- increasing power.

The findings of this research challenge the conventional wisdom about what materials could be used in the cathode of a battery. It also stimulates discussion about what such powerful batteries could be used for.

Small scale experiments so far

Increased power output makes for a great capacitor as well, by efficiently storing charge and delivering that energy precisely when it is needed. Their work, Shao-Horn said, could "lead to a device with performance that bridges batteries and electrochemical capacitors."

So far, the thickest cathode the group has made for these experiments is only 3 micrometers -- 3 one-thousandths of a millimeter. This is tiny when compared to conventional lithium-ion batteries that have electrodes roughly 100 to 200 micrometers thick.

In their present form, Shao-Horn said, their cathode "could be ideal for microelectronic devices."
But these battery-capacitors are also useful in a number of other applications such as emergency power, "energy capture and power assist in cars, trucks and machinery requiring many start-stop cycles," said Shao-Horn. Successfully scaling up this design could dramatically reduce the inefficiencies in future lithium-ion batteries.

However, Shao-Horn preferred to err on the side of caution when peering into the future of this new technology, saying they are only just beginning to understand the underlying chemistry involved.
"Further work is required," said Shao-Horn, "to demonstrate that power and energy performance is maintained with thicker electrodes." A crucial next step of this research is to demonstrate an electrode with a thickness of 50 micrometers -- more than 10 times the size of what they made for their experiments.

The next phase is scaling it up

Doing so would allow the researchers to test whether the electrical properties of the carbon nanotubes can be successfully scaled up to greater and greater thicknesses. Potentially, Shao-Horn said, there is "no limit" on thickness. But in order to do this, Hammond's expertise in biomaterials will be essential.

The layer-by-layer fabrication technique used to make the 3-micrometer-thick carbon nanotube electrode described in the published paper was an extremely time-consuming process. For each layer of nanotubes, a sample had to be dipped into a solution awash with nanotubes.

Then, covered in the solution, the sample had to be left out for 15 to 20 minutes as gravity slowly pulled the nanotubes down through the liquid and onto the sample surface. This procedure had to be repeated about 400 times in order to pile up enough layers to reach a thickness of 3 micrometers.

To bring the layering process up to reasonable, commercially viable speeds, Hammond is appropriating an automatic spray technique she developed for producing layers of polymer materials.

"The spray method is 40 to 100 times faster," she said, taking only seconds to lay down each new layer of nanotubes rather than the 15 to 20 minutes it normally takes. The true test will come once much thicker electrodes are tested.
Other battery research from Shao-Horn's group has been highlighted in other ClimateWire stories.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500
By Darius Dixon and Climatewire  | June 22, 2010

A new nanoassembly technique could make chameleon-like camouflage possible.

By using specially-designed proteins as nanomotors, Sandia National Laboratory researchers have created a system that can assemble quantum dots into bright, fluorescent rings. In this video, you can watch the formation of those rings, which are about five microns across, less than a tenth of the width of a human hair.
If these quantum dots were embedded on the surface of an object, the formation of the rings would cause the object to change color to the naked eye. Reverse the process and the color would change back. That raises the possibility of fast color changes of the sort that some animals use to blend in with their environments.
“Camouflage outfits that blend with a variety of environments without need of an outside power source — say, blue when at sea and then brown in a desert environment — is where this work could eventually lead,” George Bachand, the principal investigator at Sandia said in a press release.
But that’s probably a decade or more away, Bachand said.

Pounding the Graphene Skins

Graphene drum? Check. Laser microphone? Check. Rock on.

In a 2007 test of graphene’s ability to resonate, researchers at Pomona College in California and Cornell University in New York stretched a 2-nanometer-wide ribbon of graphene over a silicon dioxide trench, then used an electrode to vibrate the sheet.

Image: Science

Graphene Bubble

Graphene is made up of carbon arranged into chicken-wire-like hexagonal rings, yet the bonds between any carbon atoms can stretch up to 20 percent. The arrangement may seem innocuous, yet it paves the way for quantum mechanical weirdness to manifest itself.

Case in point: When scientists sandwiched graphene onto platinum, then popped out a microscopic bubble, electrons in the graphene sheet behaved as if they were being punished by a magnetic field stronger than any ever produced in a laboratory. No magnetic field was in sight, so the effect was called (naturally) pseudo-magnetism.

Image: Lawrence Berkeley National Laboratory

Ribbons 'O Graphene

To say graphene conducts electricity well is a gross understatement. The electrons buzzing around graphene’s carbon atoms are unusually free to roam and behave more like massless pieces of light called photons. This allows graphene to be used like a high-performance transistor capable of operating at speeds 100 to 1,000 times faster than silicon-based transistors.

Trouble is, graphene moves electrons around a little too well. The threshold between graphene’s on/off state is exceedingly small, causing it to conduct electricity even in an “off” state. By growing micron-thin ribbons of graphene (above) instead of full sheets, however, chemists like Hongjie Dai at Stanford University have raised that threshold more than 10,000 times. Further improvements could lead to high-speed graphene-powered electronics.

Image: Hongjie Dai/Stanford University

Graphene Transistor

Capitalizing on graphene’s electrical awesomeness, HRL Laboratories (owned by Boeing and General Motors) built the world’s first functional radio frequency (RF) transistor using graphene in 2008. The tiny device, known as an RF field-effect transistor, can pick up radio frequencies while hardly gobbling any electrical power.

The company has since scaled up a full-size chip of the transistors, but alleged practical uses in imaging and communications remain to be seen.

Image: HRL Laboratories
By Dave Mosher October 5, 2010

A new high-speed X-ray video camera, now the fastest in the world, can see through molten metal and watch weld-weakening flaws form in real-time.
 
The $670,000 device successfully captured X-ray footage on Nov. 23 at 5,000 frames-per-second (fps), or five times faster than previous X-ray cameras (and 83 times faster than a consumer camcorder). The high-speed video above shows a laser welding solid aluminum in visible light, followed by the new X-ray-light welding clips.

“With visible light, we could only see the surface of the welding process. You couldn’t see what was happening inside,” said Felix Abt, one of the camera’s designers at the University of Stuttgart. “The only way to see pores that weaken weld seams was to cut the metal into pieces.”


Automotive companies use robots equipped with high-powered lasers to seam cars together with extreme speed and precision. As laser welding continues to get “more powerful, move faster, go deeper” and increase in use, Abt says, it’s increasingly important to understand the dynamics involved.

“Laser welding creates very high-pressure, high-velocity, fluctuating environments. You’re boiling metal that’s cooling almost instantly,” Abt said. “This leads to instabilities that weaken your weld.”

To capture the welding process in action, Abt and his colleague Rudolph Weber use an industrial-strength 4-kilowatt laser, which is roughly 400,000 times more powerful than a DVD drive’s beam. As their laser pummels a hunk of metal moving on a track, a tube fires X-rays through the weld and toward a high-speed video camera.

As a frame of reference, the first clip shows 10,000 fps visible light footage zoomed in on a small 10-by-5-millimeter frame. The fuzzy 1,000 fps and 5,000 fps clips that follow are the new ones filmed in X-ray light.
“The white structure on left is where the laser hits. That’s a capillary of metallic steam,” Abt said, noting aluminum boils at 4,400 degrees Fahrenheit. Whitish globules that break off the capillary are weld-weakening pores that cool in a matter of microseconds.

The new X-ray footage isn’t pretty, Abt says, but in a few months he and Weber will tune the camera to increase its clarity. They also plan to imbue welding samples with tracer materials, such as tungsten carbide, that absorb X-rays and improve image contrast.
“This is really only the beginning, but we now have the ability to watch processes that lead to porosity in real time while we’re welding,” Abt said.

Video: A 4-kilowatt laser melts solid aluminum. The first clip is 10,000 fps in visible light, followed by 1,000 fps and 5,000 fps in X-ray light. Credit: Felix Abt, Rudolph Weber/University of Stuttgart
Image: The device Abt and Weber constructed to record laser welding in X-ray light. The laser hangs from the ceiling, the X-ray cathode is on the left (as the welding itself doesn’t produce X-rays) and the digital video camera is on the right. An exhaust vent pulls fumes away from the rig during welding and a track below moves a metal sample during recording. Credit: Felix Abt/University of Stuttgart

Over the last two years, Chinese solar panel makers like Suntech and Yingli Green Energy have moved aggressively into the United States and now supply about 40 percent of the California market, according to Bloomberg New Energy Finance, a research firm. 

China’s growing dominance of the global solar market has been on display in Los Angeles this week at the Solar Power International conference, one of the industry’s biggest annual get-togethers. In a vast exhibition hall, the booth of one Silicon Valley start-up, Solyndra, is surrounded by a sea of Chinese solar companies offering their wares. 

As prices for conventional silicon-based solar panels plummet, pressure has increased on Silicon Valley start-ups like Solyndra that make a type of photovoltaic cell called copper indium gallium selenide, or CIGS. Though less efficient at converting sunlight into electricity, the promise of the technology was that it could be made cheaply – at least until the cost of conventional solar module prices fell 40 percent over the past year.
That led Solyndra to start production two months ahead of schedule at its new $733 million factory in Fremont, Calif., and to speed up development of its next-generation solar panel. 

“It definitely puts more pressure on us to bring our costs down as quickly as possible by ramping up volume,” said Ben Bierman, Solyndra’s executive vice president for operations and engineering, as driverless carts shuttled stacks of photovoltaic parts to large orange robots at Fab 1, the company’s original factory.
Nathaniel Bullard, a solar analyst with Bloomberg New Energy Finance in San Francisco, said that success for high-tech Silicon Valley solar companies may depend on finding a big market niche they can dominate.
Solyndra, for instance, makes lightweight solar panels that snap together like Legos and can be installed on large commercial rooftops unable to support heavier conventional panels. On the roof of the company’s headquarters, Mr. Bierman recently gave me an advance look at its new solar panel, which is more powerful but requires far less labor to install. 

Production started two months early at Solyndra’s solar panel factory in Fremont, Calif.

“We really took a lot of the cost out and accelerated development in response to the Chinese,” Mr. Bierman said. 

China presents different challenges for SunPower, which was founded in 1985 and is the granddaddy of Silicon Valley solar companies. 

SunPower makes conventional solar panels but has also pursued a high-technology strategy and says it produces the world’s most efficient photovoltaic modules. (Architects and fashion-forward homeowners also favor the company’s sleek jet-black panels.)

In recent years, SunPower has increasingly focused on building big photovoltaic power plants to supply electricity to utilities that put a premium on technological performance, reliability and a company’s ability to manage complex projects.

“In the old days, the saying was that nobody gets firedfor buying I.B.M.,” Thomas Werner, SunPower’s chief executive, said in an interview. “That’s what we want to be in solar, and we are in fact.”
He said that while SunPower competes on costs, it does not aim to be the lowest-cost manufacturer.
“We want to have the best technologies so that people buy us for the reasons they buy a company’s product like Apple,” Mr. Werner said. “I don’t want to be the iPhone without the apps.”

Çin'in Güneşi Amerika'yı Yakıyor

 FREMONT, California - Silikon Vadisi girişimleri bir zamanlar güneş panelleri yapmak için kullanılan teknolojiyi yenileyip üretim maliyetlerini büyük ölçüde keserek güneş enerjisi sektörünü tepeden tırnağa değiştirmeyi hayal ediyordu. Yüksek teknoloji uzmanları tarafından kurulan şirketler sonunda seri üretime başlıyor ancak sektörün zaten değişmiş olduğunu fark ediyorlar. 

 Kendi hükümetleri tarafından sübvanse edilen Çinli şirketler, seri üretime geçip güneş panellerinin fiyatı düşürdü ve herkesi hayret ettirecek bir hızda pazarı ele geçirdi. Araştırma şirketi Bloomberg New Energy Finance'a göre, Çinli güneş paneli üreticileri ABD'nin en büyüğü olan California pazarının yaklaşık yüzde 40'ını ve Avrupa pazarlarının büyük bir kısmını ele geçirmiş durumda.

 Şanghay'daki JA Solar'ın CEO'su Fang Peng, "Her geçen yıl büyüyoruz. Bu yıl sonunda 1,8 gigawattlık kapasitemiz olacak. Ayrıca yıl başında 4 bin olan çalışan sayımız yıl sonunda 11 bine çıkacak" diyor. Kıyaslamak gerekirse, Silikon Vadisi'nde bulunan Solyndra şirketi 2011 sonunda 300 megawattlık üretim kapasitesine ulaşmayı umut ediyor. MiaSolé'nin Başkanı Joseph Laia, "Güneş enerjisi piyasası o kadar değişti ki, ağlayacak gibi oluyorum. Maliyet konusuna beklediğimizden 1 veya 2 yıl önce odaklanmak zorunda kaldık" diyor. Geniş kamu ve özel sektör desteğine rağmen Solyndra büyük zorluklarla karşı karşıya. Sektörün en büyüklerinden olan şirket, yatırımcılardan 1 milyar dolardan fazla topladı. Federal hükümet, şirketin yeni güneş paneli fabrikası için 535 milyon dolarlık kredi temin etti. Ancak Solyndra'nın fabrikası inşa edilirken, ithal edilen Çin malları yüzünden güneş modüllerinin fiyatı yüzde 40 düştü. Bunun üzerine Solyndra planlanandan iki ay önce, 13 Eylül'de panelleri piyasaya sürdü. Ayrıca daha pahalı olan panellerinin kurulum maliyeti hesaba katılınca aslında Çin mallarına göre daha uygun olduğuna müşterileri ikna etmek için bir pazarlama kampanyası başlattı. Solyndra'nın operasyonlardan ve mühendislikten sorumlu başkan yardımcısı Ben Bierman, "Pazarın durumu maliyetleri düşürmemiz için bizim üzerimizde bir baskı unsuru oluşturuyor" diyor. Bir zamanlar Silikon Vadisi'nin yeni isminin "Güneş Vadisi" olacağını öngören yatırımcılar, artık şirketlere para aktarmak konusunda daha tedbirli davranıyor. 

 San Francisco merkezli araştırma şirketi Cleantech Group'a göre, 2010'un üçüncü çeyreğinde, güneş paneli şirketlerine yapılan girişim sermayesi yatırımı 144 milyon dolara indi. Bir önceki yıl aynı dönemde bu rakam 451 milyon dolardı. Solyndra ve MiaSolé gibi bakır indiyum galyum selenyum (CIGS) kullanarak fotovoltaik hücreler üreten şirketler, bilhassa zarar gördü. Silikon plakalardan yapılan geleneksel güneş panellerinin aksine, CIGS hücreleri, cam veya esnek malzemeler üzerine yerleştirilebiliyor.

"İnce filmli" güneş panellerinin avantajı, ucuza mal edilmeleri olmalıydı ancak CIGS hücrelerinin seri üretimi beklenenden daha zor oldu. Silikon Vadisi'ndeki şirketler sorunu çözmeye çalışırken, silikon fiyatları düştü ve hükümetlerinden destek alan Çinli şirketler geleneksel güneş panellerinin üretimini hızla artırdı. Eylül ayında Sharp tarafından satın alınan güneş paneli üreticisi Recurrent Energy'nin Başkanı Arno Harris, Çin hükümeti tarafından sübvanse edilen Yingli Green Energy ile tedarik anlaşması imzalandıklarını açıkladı. Çinli şirketin ucuz ve kaliteli ürün ve finansman sunduğunu söylüyor. Harris, "Bu anlaşma sayesinde verimli şekilde finanse edilmiş projeler üzerinden rekabet edebilir teklifler verebileceğimizi fark ettik" diyor. 

 Çin'den gelen rekabet yüzünden Silikon Vadisi şirketleri alternatif stratejiler üretmek zorunda kaldı. Girişim şirketi Innovalight, "silikon mürekkep" adı verdiği ve sürülünce silikondan yapılan standart güneş hücresinin verimliliğini arttıran bir ürün geliştirdi. Innovalight yöneticileri, Çinlilerle rekabet etmek için kendi fabrikalarını kurup yüz milyonlarca dolar harcamak ve yerine ürünü Çinlilere lisanslamaya karar verdi. Innovalight'ın Başkanı Conrad Burke, "Sübvansiyon, düşük faizli krediler, ucuz işgücü ve sizi güneş enerjisinde 1 numara yapmaya çalışan bir devlet stratejisiyle nasıl baş edebilirsiniz ki?" diye soruyor. 

"Amerikan stratejisinin merkezinde inovasyon olacak. Bu Çin'deki ölçüde bir üretim sağlamayacak ancak Çin'e en son teknolojiyi satıyoruz ve burada iş olanakları yaratıyoruz" diye ekliyor. Yine de bir diğer Silikon Vadisi şirketi SolarCity'nin Başkanı Lyndon Rive, şirketinin perakende devi Wal-Mart için, çok sayıda geleneksel güneş paneli kuracağını söylüyor. Ancak bu panellerin neredeyse hepsi Çin'de üretilmiş olacak.

 By TODD WOODY

After years of research, we may be close to full-scale production of super-strong spider silk 
Mutant silkworms can produce miles of super-strong silk, in a new breakthrough that could lead to mass production of tough, flexible spider-silk material. Thanks to the efforts of these genetically modified spider-worms, along with spidergoats and spider-alfalfa, spider clothes may soon be upon us.
Randy Lewis, a molecular biologist at the University of Wyoming, has been milking his spidergoats for a couple years now, and he’s been trying to improve yields of genetically engineered spider-silk alfalfa. He’s researching improved synthetic spider silk genes, and he hopes to start growing spider cotton in the near future. With his latest research, spider fabrics might only be a year away.

Last week, Lewis and Malcolm Fraser at the University of Notre Dame announced they bred silkworms that had been genetically engineered to produce spider silk.

“From our perspective, there are huge advantages to the fact that the fiber is already spun,” Lewis said. “You don’t have to purify the protein, you don’t have to take it and spin fibers.”
Lewis said the study, which has not yet been published, proves the concept of engineering and breeding transgenic silkworms.

“The real question is going to be, can we make the necessary improvements in the mechanical properties of the silkworm silk by incorporating the spider silk in it? If we can do that, then obviously it makes a whole lot of things possible in terms of the amount of material you can make.”
A single silkworm cocoon contains more than a half-mile of silk thread, so colonies of transgenic silkworms produce plenty of silk, said Fraser, a molecular biologist at Notre Dame. He believes industrial production of engineered spider silk could happen within a year.

Spider silk is one of the most valuable materials in nature. It could be used for a vast array of products, from artificial ligaments to super-strong wound dressings or even body armor. Lewis envisions spider-silk replacement tendons, parachute cords and more.

Silk could even be used to transport drugs or act as nanoscale transistor scaffolds. In a study last year, scientists at Legacy Clinical Research & Technology Center in Portland, Ore., demonstrated that silk-based brain implants containing adenosine can suppress seizures in rats. In a paper published in the journal Science in July, Tufts University researchers said silk could be used to build flexible and degradable displays or even implantable optical systems for medicine.

“There’s lots of things you can do with fibers that you can’t do with something that comes as an amorphous blob or a solid,” Lewis said.
Nano-fabrics could be even stronger than spider silk, but as of now they’re impossibly small. Last week, Canadian researchers reported building the longest-ever polyyne chain — polyyne carbon-carbon bonds are even stronger than those in graphene — but it was only 44 carbon atoms long.

Nano-sized fibers are still limited. “We can make textile quantities of the silkworm silks,” Fraser said. “Nanotechnology is certainly something that has some awesome potential, but I don’t know how soon that potential will be realized, and even if it is realized, I’m not sure that it would replace many of the medical applications of natural silk fibers, which are considerable.”

Lewis has been working on those applications for two decades. It’s been 12 years since he first isolated the genes that produce high-performance spider silk, and he garnered international attention for his transgenic goats, whose DNA has been altered to produce the proteins necessary to make spider silk. When the goats give birth and start lactating, they produce spider silk proteins in their milk, which is collected, purified and spun into silk, Lewis said.

It would be easier to milk spiders than mutant goats, if only spiders were not so murderous and territorial. As it is, spider farms have not proven a successful venture, whereas there are long traditions of farming both silkworms and goats. Scale makes a difference too: Lewis can get half an ounce of silk from every quart of milk. It would take 100 spiders to obtain that amount.

Transgenic silkworms could be even more productive. Breeding them involved some sneaky DNA, however. Kraig Biocraft Laboratories Inc., a Lansing, Mich., firm, partnered with Fraser, who discovered and patented a DNA transposon called “piggyBAC.” The transposon can insert itself into a cell’s genetic material. The researchers used piggyBAC to incorporate snippets of spider DNA into silkworm embryos, resulting in silkworms that spin a hybridized part-silkworm, part-spider silk.

The researchers wanted to be sure they could breed the spiderized silkworms, so they also added fluorescent protein to the spider DNA. The mutant silkworms had glowing red eyes, and their silk was fluorescent green.
Fraser said he is completing molecular analyses before submitting his study to a research journal. Meanwhile, he hopes to continue improving the snippets of spider DNA — especially if scientists obtain a sequence for a brand-new spider just discovered in Madagascar. The Darwin’s bark spider makes the largest webs in the world, spinning silk that is 10 times stronger than Kevlar.

Fraser also studies HIV and hepatitis, and he hinted that piggyBAC-hacked silkworms might be useful for other applications: “Silk isn’t the only protein that silkworms can produce,” he said.
Lewis said his highest priority is figuring out the fastest and most efficient way to produce large quantities of silk. He also hopes to continue isolating new spider silk genes and incorporating them into his formula. As of now, his formula is a blend of several different spider proteins, mainly from the golden orb weaver.
Lewis also hopes to start breeding cotton plants that contain the protein necessary to make spider silk. Cotton seeds already contain protein, and they’re considered a waste product, Lewis said.

“If we can take and use something that nobody is going to eat and that doesn’t have much value, and use that as a production system, then we have very little impact on food and fiber, and we can use the methods that are already out there,” he said.

Then spider clothes might not be far off at all.

Lasers can be powerful weapons — they can take down an aircraft at long ranges and in unstable conditions, for instance. But they are hampered by power and size limits, so they’re not widely used by the military (yet).
Lockheed Martin has a solution: a fiber laser that basically works like a backward prism.

Lockheed is among three firms recently awarded contracts to develop a laser for the military’s Robust Electric Laser Initiative, which seeks to improve the power of electric lasers. Fiber lasers are efficient and compact, but until now they have been weaker than other types, like chemical lasers. The RELI program seeks to improve laser strength while reducing power and cooling, so systems can be small enough to install on ships or airplanes.

A Lockheed subsidiary developed a first-of-its-kind high-powered fiber laser capable of producing 100 kilowatts or more, according to Lockheed. It uses fiber optics to produce near-perfect beams. The method also confines the laser light to the fiber’s glass structure without using mirrors or other optics.
John Wojnar, director of business development for the laser systems business, said in a September issue of Aviation Week that it works like a inverse prism: lasers with slightly different wavelengths enter a combiner, and the result is a single, focused beam. It’s called Spectral Beam Combining.
Lockheed won an initial $14 million contract from the US Army Space and Missile Defense Command to develop the system. Along with General Atomics and Raytheon, the firm must demonstrate a 25 kW system that can be scaled up to 100 kW within five years.
General Atomics will improve its Hellads distributed-gain laser approach to improve efficiency, while Raytheon will pursue a planar waveguide laser, according to Aviation Week.
Northrop Grumman is also expected to obtain a RELI contract.

Stephen Steiner wants to make nanotechnology more accessible to speed up the innovation process.

Researchers have developed a new material that can fill in its own surface cracks.

Researchers at the University of Illinois at Urbana-Champaign (UIUC) have made a polymer material that can heal itself repeatedly when it cracks. It's a significant advance toward self-healing medical implants and self-repairing materials for use in airplanes and spacecraft. It could also be used for cooling microprocessors and electronic circuits, and it could pave the way toward plastic coatings that regenerate themselves. 
Modeled on human skin, a new material that heals itself multiple times is made of two layers. The polymer coating on top contains tiny catalyst pieces scattered throughout. The substrate contains a network of microchannels carrying a liquid healing agent. When the coating cracks, the cracks spread downward and reach the underlying channels, which ooze out healing agent. The agent mixes with the catalyst and forms a polymer, filling in the cracks.  Credit: J. Hanlon, Univ. of Illinois Beckman Institute 

The first self-healing material was reported by the UIUC researchers six years ago, and other research groups have created different versions of such materials since then, including polymers that mend themselves repeatedly when subject to heat or pressure. But this is the first time anyone has made a material that can repair itself multiple times without any external intervention, says Nancy Sottos, materials-science and engineering professor at UIUC and one of the researchers who led the work.
"It's essentially like giving life to a plastic," says Chris Bielawski, a chemistry professor at the University of Texas at Austin. The ultimate goal would be to create materials that mend themselves, he says, and "this is an amazing proof of concept."

Sottos and her colleagues have designed the new material, reported in this week's Nature Materials, to mimic human skin. If the skin's outer protective layer is cut, the inner layer, which is infused with a dense network of tiny blood vessels, rushes nutrients to the cut to help with healing. The self-healing material consists of an epoxy polymer layer deposited on a substrate that contains a three-dimensional network of microchannels. The epoxy coating contains tiny catalyst particles, while the channels in the substrate are filled with a liquid healing agent.

To test the material, the researchers bend it and crack the polymer coating. The crack spreads down through the coating and reaches the underlying microchannel. This prompts the healing agent to "whip through the channels and into the crack," Sottos says. There, it comes into contact with the catalyst and, in about 10 hours, becomes a polymer and fills in the crack. The system does not need any external pressure to push the healing agent into the crack. Instead, the liquid moves through the narrow channels just as water moves up a straw.

The researchers are able to crack and reheal the surface as many as seven times before the catalyst wears out and stops working. The next generation of the self-healing material should be able to heal itself many more times, according to the researchers. Sottos and her colleagues are designing it so that it will have a two-part system that injects both a healing agent and a catalyst into the crack.
The researchers could also increase the rehealing capacity of the material by hooking up the microchannel network to a little reservoir, Sottos says. If the material runs out of healing agent or catalyst, the reservoir could pump in more.

The material's microchannel design could be a solution to the increasing problem of heat buildup in microelectronics chips. Typically, microelectronic circuit chips sit on substrates that are designed to conduct heat away from the circuit. These heat regulators have their limits. Instead, Sottos says, "you could put a cooling fluid through a [microchannel] network like a little mini-heat exchanger."

Sottos says that researchers could use the same design with other resin and catalyst combinations that can form different polymers. This opens the door for many other applications. While practical self-healing materials might be years away, it's easy to imagine their applications in prosthetics and medical implants made from biocompatible self-healing materials. The cost of the materials might keep them limited, at least initially, to certain high-value, high-performance applications such as use in air- and spacecraft, says Ian Bond, aerospace engineering professor at the University of Bristol, in the United Kingdom.

In the future, different chemistries could lead to cheaper self-healing materials, according to Bielawski. "You could use cheap epoxies ... that you can buy at Home Depot ... as a healing agent," he says.

Prachi Patel - technologyreview.com