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Laser Light Can Lift Tiny Objects

Light has been put to work generating the same force that makes airplanes fly, a study appearing online December 5 in Nature Photonics shows. With the right design, a uniform stream of light has pushed tiny objects in much the same way that an airplane wing hoists a 747 off the ground.

Researchers have known for a long time that blasting an object with light can push the object away. That’s the idea behind solar sails, which harness radiation for propulsion in space, for instance. “The ability of light to push on something is known,” says study coauthor Grover Swartzlander of the Rochester Institute of Technology in New York.

Light’s new trick is fancier than a boring push: It created the more complicated force called lift, evident when a flow in one direction moves an object perpendicularly. Airfoils generate lift; as an engine propels a plane forward, its cambered wings cause it to rise.

Lightfoils aren’t about to keep an Airbus aloft for the time it takes to fly from JFK to LAX. But arrays of the tiny devices might be used to power micromachines, transport tiny particles or even enable better steering methods on solar sails.

Optical lift is “a really neat idea,” says physicist Miles Padgett of the University of Glasgow in Scotland, but it’s too early to say how the effect might be harnessed. “Maybe it’s useful, maybe it’s not. Time will tell.”
That light can have this unexpected lift effect started with a very simple question, Swartzlander says: “If we have something in the shape of a wing and we shine light through it, what happens?” Modeling experiments told the researchers that an asymmetrical deflection of light would create a surprisingly stable lift force. “So we thought we’d better do an experiment,” Swartzlander says. “Because this just looks too pretty.”

The researchers created tiny rods shaped kind of like airplane wings — flat on one side and rounded on the other. When these micron-sized lightfoils were immersed in water and hit with 130 milliwatts of light from the bottom of the chamber, they started to move up, as expected. But the rods also began moving to the side, a direction perpendicular to the incoming light. Tiny symmetrical spheres didn’t exhibit this lift effect, the team found.
Optical lift is different from the aerodynamic lift created by an airfoil. A plane flies because air flowing faster under its wing exerts more pressure than air flowing above. But in a lightfoil, the lift is created inside the object as the beam shines through. The shape of the transparent lightfoil causes light to be refracted differently depending on where it goes through, which causes a corresponding bending of the beam’s momentum that creates lift.

These lightfoils’ lift angles were about 60 degrees, the team found. “Most aerodynamic things take off at very gradual angles, but this has a very striking, very powerful lift angle,” Swartzlander says. “You can imagine what would happen if your airplane took off at 60 degrees — your stomach would be in your feet.”
As the rods lift, they shouldn’t stall out, the paper predicts. “The subtlety is that it actually self-stabilizes,” Padgett says. “It twists a little bit one way, and you think, ‘Oh dear, it’ll stop working,’ then the light rotates it back again.”
Swartzlander says he hopes to ultimately test the lightfoils in air, too, and try different shapes and materials with various refractive properties. In the study, the researchers used ultraviolet light to generate the lift, but other kinds of light would work just as well, Swartzlander says. “The beautiful thing about this is that it would work as long as you have light.”

Video: Riding a beam of light, a tiny particle thousandths of millimeters in size is pushed sideways by the same force that keeps airplanes aloft. Credit: Swartzlander et al.

Laura Sanders, Science News December 6, 2010 - Wired Mag.

See Also http://www.sciencenews.org/view/generic/id/67050/title/Light_can_generate_lift

Archive Gallery: How Science Made Movies Awesome

Popular Science has been around for 138 years, which gives us a couple of decades on the first commercial motion pictures. After the use of narrative and orchestra music became integral to cinema, filmmakers devoted themselves to elevating movies from experimental form of entertainment into an art form. Not only were we there to break the news when movies finally played sound, but we were privileged enough to receive a couple of enlightening articles from Charles Francis Jenkins, who helped invent the television, and D.W. Griffith, who is credited for creating America's first feature film.

3-D Movies are Here: January 1923

Although Avatar heralded a new, oft-debated era of 3-D movies in late 2009, James Cameron's technology was actually predicated by that of DW Griffith, who previously created The Birth of a Nation, America's first blockbuster. In 1923, movies still lacked color and sound, but Griffith claimed to have developed stereoscopic movies that "would drive startled spectators from their seats." Here's how it'd work: a stereoscoping movie camera would exposes red and green, left and right films simultaneously while filming. Audiences would watch movies using an alternating shutter device, which would filter double-image pictures so that the viewer sees the "right" picture with his right eye, and then the reverse an instant later. How's that for a predecessor to 3-D glasses?

Future Movie Theater: April 1923

The 1920's saw a revolution in movie theater design. Before, people watched movies in five-cent nickelodeon theaters, but once full-length feature films became the norm, studios began building theater chains and movie palaces, which were renowned for their luxuriously large screens and spacious interiors. Samuel Lionel "Roxy" Rothafel, who went on to open New York's Radio City Music Hall in 1932, predicted that movie houses of the future would supplement screens would color-light paintings on curved walls. He envisioned auditoriums holding 5000 persons. While the movie played, hidden projectors would "paint" the walls with moving scenery, giving viewers the illusion that they were actually in the movie. Meanwhile, a hidden orchestra would provide music and sound effects. Although Rothafel's ideas ended up being more compatible with Broadway shows than with film, he is credited for the idea of synchronizing orchestral music with movie scenes.

Hooray, Live Sports Parties: May 1923

Earlier this year, millions of people around the globe gathered outdoors to watch live broadcasts of the FIFA World Cup. viewing parties are so ingrained in sports culture nowadays that it's difficult to imagine depending on newspapers or word-of-mouth to find out who won a big game.

In 1923, Charles Francis Jenkins, who helped invent the television, announced plans to broadcast motion pictures of world events and sporting games over radio airwaves. Although commercial radio had just begun airing live sports broadcasts, Jenkins was eager to take the technology further with an apparatus that could transmit one photograph every four minutes.His machine worked by using rapdily rotating circular prisms to cast lights and shadows onto a selenium cell in an electric circuit, which would convert the light into wireless waves. Admittedly, his invention needed work, but Jenkins was confident that with a little work, he would be able to broadcast live news events to far-off places. Since skeptics (okay, Popular Science) asked how the sun's glare would let them see outdoor broadcasts of baseball games, Norman Furber, a New York City inventor invented a special screen that could reflect images clearly as long as the sun didn't shine directly on it.

D.W. Griffith Explains Cinematic Technique: June 1926

Prior to The Birth of a Nation most films were merely recordings of subjects moving about: there were no close-ups, no experimental angles, and no use of shadows. Despite his controversial legacy as the creator of a highly racist film, D.W. Griffith is widely credited with pioneering the use of light and camera angles as a cinematic technique. In an article written specially for our publication, Griffith elaborated on how he manipulated light to heighten mood and tension. For instance, he used mirrors to replicate the effect of sunlight streaming through the trees. He also developed the reverse light technique, which placed light in front of the object in focus instead behind it, as was customary at the time. Much to the suprise of his colleagues, Griffiths' technique actually made subjects look much more natural. Moreover, he introduced the soft focus, or the gentle blurry effect achieved by photographing an image through multiple lenses.

Of course, there were plenty of light-related issues that continued to stump Griffith. Blonde hair and blue eyes did not register well in front of the camera, and actors struggled to film "ardent scenes" under the temperature of glaring lights. "I hope that cold light will soon replace the super-hot ones," Griffith said. "It will make action more effective."

How Talking Movies Work: November 1926

A year before The Jazz Singer premiered, audiences at a theater in New York watched in awe as images of a violinist, a vocalist, and an actor talked and played music from the movie screen. Engineers achieved this effect using the vitaphone, a new invention hailed as the long-awaited breakthrough in talking movies. As the diagram pictured left shows, the machine worked by recording sound on a master disk, while two electrically interlocked motors synchronized images with the sound. While filming, the camera would record images while a microphone on the ceiling would record sound and convert it to electrical impulses, which traveled through a vacuum tube to an amplifier. The impulses would then form groove formations on the sound disk. In the theater, an image projector and the sound disk operated from different ends of a motor. While the images played, a needle would translate the disk's impressions into electrical surges, thus creating amplified sound.

As you can see in the artist's diagram, one horn-shaped projector would transmit sounds recorded on the film, like the dialogue, while two other horns would transmit the orchestra accompaniment. Not long afterward, The Jazz Singer would use this very technology to become the first feature-length film with synchronized dialogue.

Behind the Scenes at a Talkie Studios: April 1929

The rise of talkies not only revolutionized the movie-going experience, but it completely upended the acting industry. Actors with thick accents or weak vocal deliveries, like It Girl Mary Pickford, fell from stardom. Norman Foster, a former Broadway Stage actor who had transitioned to talking movies, contributed an article describing how producers recorded dialogue in the new "talking movie studios." He recalled how strict Paramount was was about noise level -- evidently, the soundproof technology weren't too effective, as producers were tasked with both refining sound and keeping out superfluous noises. To ensure the crispness of recordings, studios were built with terra cotta tile walls and double doors. Felt carpets and curtains made of monk's cloth deadened footsteps and echoes.

To record sound, studio engineers would hang stage microphones on set. The sound would travel through a wire to the monitor room, where the operator would make the sound more natural by tweaking the volume of transmissions. From the monitor room, the transmission would travel to the sound room, where it would be recorded and played back for the director after shooting finished.

The Advent of Newsreel Cinemas: August 1930

Back in the day, newsreels were a hallmark of the movie-going experience--since we hadn't quite reached the era of personal televisions yet, people watched the news in newsreel cinemas, which often aired entertainment programs in addition to actual news. At the time this article was written, newsreels were hailed as "talking newspapers" because people were in awe at how stories could appear in theaters before going to print. Moreover, being able to hear and see disasters -- buildings consumed by flame, soldiers dying on the battlefield -- made world events all the more harrowing. Viewers could barely get enough of it. Three companies, Fox, Paramount, and Pathe, distributed sound newsreels to 12,000 special news cinemas all of the country. The heart of the newsreel culture, was of course, in New York, where its Newsreel Theater presented hourly newsreels from 10 AM until midnight.

Thanks to the advent of newsreel cinemas, journalism changed practically overnight. Previously, gathering pictorial news required only a guy with a camera; now, companies needed a sound truck, cameras, microphones, and other expensive equipment to keep up.

How to Create Special Effects: March 1933

Much like today, up-and-coming independent filmmakers worked steadily in the shadows of their big-budget Hollywood counterparts. Curious to see how amateur filmmakers created special effects with limited equipment and finances, we paid a trip to the set of The Lunar Expedition, which was located in the garage of two Los Angeles filmmakers. While there, we were struck by the ingenuity of their meticulously constructed scale models and special effects. The illustration at left shows how they filmed a scene where the rocket flies through a storm. First, they built small model rocket out of metal and illuminated its insides with a tiny bulb. Cotton was used for the clouds, while water dripping down a glass panel served as the rain. Lamplight filtered through a cut-up photo of clouds blinked on and off to simulate lightning.

The First Drive-In Theater: August 1933

Nowadays, drive-in theaters seem like a cute relic of the past, but in the early 1930's, they were slated to be the next big trend in movie-going. For the next two decades, they entertained teenagers on dates and distressed parents who grew concerned about what their kids were doing in those filthy "passion pits." Back to the 1930's though--the drive-in debuted in Camden, N.J., where families were free to watch movies without worrying about their children's noisiness. A month after the theater opened, we reported that a new system of directional sound projection allowed audiences to hear dialogue as clearly in the back row as they could in the front. The pit could also occupy 400 cars, which were parked on levels inclined in a way so that vehicles didn't obstruct anyone's view.

Mobile Theater: April 1937

In 1937, New Jersey struck again: a local inventor unveiled a truck that doubled as a mobile movie theater. A projector mounted in the rear of the truck transmitted the film through an inclined mirrors and onto a translucent screen. The truck came equipped with twelve loudspeakers, six on each side, and a gasoline engine within the truck body for generating electricity. We predicted that politicians would one day use mobile theaters for campaigns.

By Denise Ngo Posted 12.03.2010 - Popular Science

Antimatter held for questioning

Magnetically trapped atoms could test fundamental physics.
Eugenie Samuel Reich

For physicists, a bit of antimatter is a precious gift indeed. By comparing matter to its counterpart, they can test fundamental symmetries that lie at the heart of the standard model of particle physics, and look for hints of new physics beyond. Yet few gifts are as tricky to wrap. Bring a particle of antimatter into contact with its matter counterpart and the two annihilate in a flash of energy.

Now a research collaboration at CERN, Europe's particle-physics lab near Geneva, Switzerland, has managed, 38 times, to confine single antihydrogen atoms in a magnetic trap for more than 170 milliseconds. The group reported the result in Nature online on 17 November¹. "We're ecstatic. This is five years of hard work," says Jeffrey Hangst, spokesman for the ALPHA collaboration at CERN.

The electrodes (gold) of the trap used to combine positrons and antiprotons to form antihydrogen. N. MADSEN, ALPHA/SWANSEA

An antihydrogen atom is made from a negatively charged antiproton and a positively charged positron, the antimatter counterpart of the electron. The objective — both for ALPHA and for a competing CERN experiment called ATRAP — is to compare the energy levels in antihydrogen with those of hydrogen, to confirm that antimatter particles experience the same electromagnetic forces as matter particles, a key premise of the standard model. "The goal is to study antihydrogen and you can't do it without trapping it," says Cliff Surko, an antimatter researcher at the University of California, San Diego. "This is really a big deal."
The ALPHA claim is the first major advance since the creation of thousands of antihydrogen atoms in 2002 by a forerunner experiment called ATHENA² and by ATRAP³ (see 'A brief history of antimatter'). Both experiments combined decelerated antiprotons with positrons at CERN to produce antihydrogen atoms. But, within several milliseconds, the atoms annihilated with the ordinary matter in the walls of their containers.

To prevent that from happening, the ALPHA team formed antihydrogen atoms in a magnetic trap. Although not electrically charged like antiprotons and positrons, antihydrogen — like hydrogen — has a more subtle magnetic character that arises from the spins of its constituent particles. The ALPHA researchers used an octupole magnet, produced by the current flowing in eight wires, to create a magnetic field that was strongest near the walls of the trap, falling to a minimum at the centre, causing the atoms to collect there. To trap just 38 atoms, the group had to run the experiment 335 times. "This was ten thousand times more difficult" than creating untrapped antihydrogen atoms, says Hangst — ATHENA made an estimated 50,000 of them in one go in 2002. To do spectroscopic measurements, Surko estimates that up to 100 antihydrogen atoms may need to be trapped at once.

ATRAP still hopes to reach that goal first. In a paper due out in Physical Review Letters, the collaboration reports that it has efficiently separated antiprotons from the cold electrons that are used to cool them down, a step towards creating slower-moving antihydrogen atoms that might stay trapped for longer. "Rather than trying to demonstrate that we can confine 38 antihydrogen atoms for a small fraction of a second, we are working on new methods to produce and trap much larger numbers of colder atoms," says Gerald Gabrielse, ATRAP's spokesman. "We shall see which approach is more fruitful."

Two other collaborations aim to study antihydrogen. In 2003, the international ASACUSA experiment at CERN proposed a scheme to create a beam of antihydrogen atoms⁴. Yasunori Yamazaki, an atomic physicist at the Advanced Science Institute in Saitama, part of Japan's RIKEN network of research labs, now says the group has produced such a beam and may be able to use it to study the energy levels in antihydrogen without needing to trap the atoms. Another CERN experiment called AEgIS is starting to compare the effect of gravity on antihydrogen with that on ordinary hydrogen. Antimatter is almost certain to fall at the same rate as normal matter, but if it doesn't the results could help scientists to distinguish between alternative approaches to unifying quantum theory with general relativity.

Published online 17 November 2010 | Nature 468, 355 (2010) | doi:10.1038/468355a

World’s Most Powerful Laser on Target for Awesome Science

Scientists recently pulled together the pieces of the world’s most powerful laser and, in a first-ever complete dry run, pulled the trigger on a peppercorn-sized pellet of nuclear fuel. The energy crushed the capsule instantly, causing it to spew a shower of neutrons. In short: It worked.
The firing of the National Ignition Facility, or NIF, at Lawrence Livermore National Laboratory, located 40 or so miles east of San Francisco, wasn’t an earnest attempt at a more-energy-out-than-you-put-in “ignition” of fusion, the same process that merges atoms at the sun’s core — and the facility’s ultimate goal. Yet the staff and independent researchers working with the $3.5 billion machine have reason to be optimistic about achieving fusion within two years, even if much of the device’s time is earmarked for defense research and prospects of near-limitless and pollution-free energy aren’t certain.
“In my mind, to have accomplished this shot is an almost unfathomable scientific achievement,” Paul Drake, a physicist at the University of Michigan using NIF as a proving ground for studying supernova physics in the laboratory, told Wired.com. “I’ve had a lifetime of experience of big science facilities, and find myself in awe of [the NIF team] having made this thing work this fast.”

The research facility’s construction began in 1997 and spreads over an area nearly the size of three pro league football fields, most of the space occupied by equipment that revs up 192 laser beams. During the Sept. 29, 2010 firing of the laser, scientists and engineers funneled these beams into a 30-foot-diameter metal sphere at the end of the complex. At the center of this chamber, a tiny plastic pellet filled with heavier forms of hydrogen received a punishing 1 megajoule zap, similar to the instantaneous oomph of a car traveling 100 mph.
According to engineering physicist Edward Moses, who heads up the NIF team, the laser burst was about 75 percent of its full energy capacity. In addition, the cryogenically cooled pellet was filled with deliberately less-than-perfect fuel.
“The last thing we’d ever think about doing is playing cowboy with this thing,” Moses said. Throughout the next year or two leading up to an all-or-nothing firing, the facility will make similar integrated shots about once a month.
Richard Petrasso, a fusion scientist at MIT who works with the machine’s diagnostic equipment, said the tiptoeing is for a good reason.
“The facility is like a new car engine,” Petrasso said. “You don’t hit the pedal all the way down to the ground the first time. You have to tune it to get all of the conditions just right — the laser, the diagnostics and the surface of the capsule.”
About 10 trillion neutrons zoomed out of the capsule during the test shot, signaling the successful fusion of some tritium and deuterium atoms — the “heavy” hydrogen fuels in the pellet. Moses said 1,000 times more neutrons should fly out during the ultimate goal of a fusion chain reaction.
At that point, if the machine can actually do it, Drake said the scientific payoffs will be huge.
“We’re still proving we can do experiments we want, and also for the broader scientific community,” Drake said. “But without hesitation, I’d say NIF is on track for doing some pretty awesome science,” including simulating Jupiter’s oddly magnetic core, the innards of stars and other hot-and-dense environments around the universe.

At the end of the day, however, most of NIF’s operating time isn’t slated for doing fundamental science. Moses said about 10 percent of the machine’s time is dedicated to that now and will go up to 20 percent after 2013. Another 40 percent (by 2013) is hedged for more ignition research, and the remaining 40 percent chunk will be for gathering data about fusion physics for the government. In other words, it will simulate fusion bomb explosions without detonating them.
“Strategic security is also part of the mission,” Moses said. “We want to make sure we can build virtual test sites on computers, but we need good data to ground the models.” If NIF achieves fusion burn, he said it will be the only facility of its kind to safely create the conditions of active weapons.
Beyond NIF’s three-pronged mission, there’s also the promise of developing a safe fusion energy source that releases 30-40 times the energy put in. The only theorized “pollution” would be helium, which is the universe’s most pervasive and inert gas.
“The energy potential is there, for sure,” Petrasso said. “The question is about practical implementation. There are a lot of … issues that have to be dealt with to turn it into a reactor that makes energy.”

Images: Lawrence Livermore National Laboratory. 1) Inside the National Ignition Facility’s 10-meter-diameter target chamber. 2) NIF’s laser bay. 2) The container of the tritium/deuterium fuel pellet, called a “hohlraum.” Video: Wired.com

How Modified Worms and Goats Can Mass-Produce Nature's Toughest Fiber

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.

Silkworm: A mature silkworm is pictured just before it starts spinning its transgenic silk. University of Notre Dame

“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.

In New Attempt to Build a Practical Military Laser Weapon, Lockheed Inverts a Prism

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.

Laser-Powered Warfare Lockheed's RELI laser, developed under a DARPA contract, works like an inverse prism to focus several different wavelengths of laser light. Lockheed Martin

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.

Casimir effect put to work as a nano-switch

A new technique that takes control of the Casimir effect – a strange quantum phenomenon that gums up nanoelectromechanical systems (NEMS) – may pave the way to a switch that could cut the power consumption of nanoscale gadgets.

The Casimir effect tends to force together two parallel conducting plates when they are a few micrometres apart or less. It arises because of the quantum electromagnetic fluctuations that always occur in a vacuum. The close proximity of the two plates constrains the fluctuations in the gap between them. This makes the fluctuation between the plates weaker than those in the surrounding space, so the plates are pushed together.

The effect was named after Dutch physicist Hendrik Casimir, who predicted its existence in 1948. Nanotechnologists are keen to tame it, because it gums up their nanoscopic machines.

A European research team has now done just that, using a material already used in rewritable CDs and Blu-ray discs. AIST, an alloy of silver, indium, antimony and tellurium, reversibly switches from a crystalline to an amorphous state when heated by a laser, allowing data to be written and rewritten onto a disc.

Golden ball

The team deposited AIST on an aluminium-coated silicon wafer and held it between 40 and 120 nanometres from a gold sphere in an ultra-high vacuum. When AIST was in an amorphous form, the Casimir force measured about 100 piconewtons, but it increased by 20 to 25 per cent when the AIST was in its crystalline form.

This is because the crystalline phase is more reflective, so it confines the electromagnetic fluctuations more effectively and so increases the Casimir force.

Group member George Palasantzas at the University of Groningen in the Netherlands says this phenomenon could be used to build a new type of low-power nanoswitch. The switch would be physically moved by altering the state of the AIST, and so changing the strength of the Casimir force.

"The state remains stable even when power is turned off, which is a unique feature," Palasantzas says – unlike existing nanoswitches, such as those used to switch the transmission frequency in mobile phones.

Davide Iannuzzi of the Free University in Amsterdam, the Netherlands, who was not involved in the study, says it is "an important contribution", though he warns that in real applications, the build-up of electric charge between moving parts may have more of an effect on the nanoswitch than the Casimir force. "If one finds an easy way to control the [electric charge], then the Casimir force becomes indeed interesting – but that is quite a challenge," he says.

Palasantzas, however, predicts that ways will be found to minimise the electrostatic build-up, so that the Casimir force exceeds the electrostatic force for distances below about 100 nanometres.

Journal reference: Physical Review A, in press

Work light twice as hard to make cheap solar cells

"Third-generation" solar cells that could shatter the efficiency limit of conventional cells have come a step closer. A proof-of-concept device is the first to generate twice the standard current produced from the most energetic photons in sunlight.

A photon arriving at a solar cell needs a certain amount of energy to break an electron free from its atom and generate current. However, photons with energy above that threshold still generally release only a single electron, generating no additional current even if they arrive with more than enough energy to free two electrons.

In 1961, semiconductor pioneers William Shockley and Hans Queisser showed that the these factors limited single solar cells to converting no more than 31 per cent of incident solar energy to electrical energy. But around a decade ago Martin Green of the University of New South Wales in Sydney, Australia, challenged that orthodoxy. He suggested the third generation of solar cells could break the 31 per cent barrier.

Breaking the limit

Earlier this year, a team from the universities of Texas and Minnesota offered one way to break through the barrier, by capturing extra energy lost as heat after the electrons escape their atoms. Now Bruce Parkinson and Justin Sambur at the University of Wyoming in Laramie, and Thomas Novet of Voxtel in Beaverton, Oregon, have taken the first steps along another route to super-efficient solar cells. Their approach involves harnessing particularly energetic photons – those with more than twice the energy needed to free an electron – and using them to free two electrons rather than one, potentially doubling the current generated.

The process had already been seen in macroscopic semiconductors, but it has been extremely inefficient. Seeking better results, Parkinson and colleagues turned to quantum dots, tiny chunks of semiconductor that confine current carriers in nanometre-sized volumes.

Parkinson's team coated a smooth titanium dioxide electrode with a single layer of lead-sulphide quantum dots. The quantum dots chosen must absorb between 0.85 and 1.39 electronvolts to free up one electron.

The researchers illuminated the device with a variety of wavelengths of light. Using reddish light in which individual photons carry 1 to 2 electronvolts, 70 to 80 per cent of the relatively small number of photons absorbed by the device freed up an electron. But then the team switched to light from the blue end of the spectrum, where individual photons carry over 2.4 electronvolts, which is 2.7 times the threshold for freeing electrons. Now they collected an excess of electrons, up to about double the number of absorbed photons. This strongly suggests that many of the photons were generating two electrons.

Super-cheap cells

"It's very good science," says Michael Naughton of Boston College. The demonstration of collecting the electrons is an important step toward future solar cells, he says.

"This is a first step," Parkinson told New Scientist. The single layer of quantum dots used in the experiment is so thin that it absorbed only a little of the incident light and total efficiency was very low. But he expects others to refine the technique and boost total efficiency.

The quantum-dot solar cell technology could replace dyes in dye-sensitised solar cells. These cells presently have a peak production efficiency of around 11 per cent, but it is "cost per watt" that is the most important metric, says Parkinson, and quantum-dot sensitised solar cells could be very cheap to make. "What we need is a 12 to 15 per cent efficient solar cell that you can manufacture for a cost not much more than newsprint."

Journal reference: Science, DOI: 10.1126/science.1191462

Invisibility cloaks and how to use them

The "invisibility cloaks" being made in labs today can hide objects when viewed from a wide range of directions and in visible light – both considered implausible developments when the first working invisibility cloak was demonstrated just four years ago. But the technology that makes objects vanish looks set to be more useful for the safety of offshore structures and for unlocking cosmological secrets than for would-be Harry Potter impersonators.

In 2006, John Pendry's team at Imperial College London made the news with a design for a cloak that could steer light around an object to render it invisible. Within months a team led by David Smith of Duke University in Durham, North Carolina, had built such a device using exotic "metamaterials" – materials with unusual electromagnetic properties that are not found in nature.

But that first cloak could only hide two-dimensional objects viewed from specific directions – and only if they were "viewed" using one particular microwave frequency. Producing a cloak to hide objects from visible light, which has a wavelength several orders of magnitude smaller than microwaves – let alone cloaking objects when viewed from any direction – seemed a more remote possibility.

Just four years later that's no longer the case. "While full cloaking has not been achieved, it shows promises in the right direction," says Ulf Leonhardt at the University of St Andrews, UK.

Carpet trick

Last year, physicists at the University of California, Berkeley, and Cornell University in Ithaca, New York, independently built optical-frequency cloaks. These were so-called carpet cloaks, made from silicon, which were placed over the object to be cloaked. The object created a bump in the carpet, but the carpet appears flat when light arriving from a specific direction reflects off the surface.

For now, such technology can cloak only objects with a surface area of a few square micrometres and a few hundred nanometres deep. But "in principle, you can make the [cloaked] object larger and larger", says Thomas Zentgraf, a member of the Berkeley team.

Another limitation of the technology – that it works for specific viewing angles only – is already being overcome. Earlier this year, Tolga Ergin of the Karlsruhe Institute of Technology in Germany and colleagues demonstrated a version of the technology that could hide an object from view from a wider range of directions, bringing 3D cloaking a step closer. They arranged photonic crystals in a woodpile-like stack, filling the gaps between the crystals with varying amounts of a polymer to control the refractive index of the metamaterial. This changed the refractive index to a differing degree across the metamaterial, allowing it to mask a bump in a gold foil over a wide viewing angle of about 60 degrees.

"We are optimistic that we can do this [for any viewing angle] in a few years," says Zentgraf.

Waves and event horizons

But even 2D cloaking technology could have real-world uses. Stefan Enoch at the Fresnel Institute in Marseille, France, and colleagues have shown that metamaterials could guide waves around offshore structures, protecting them from storms or tsunamis.

Meanwhile, metamaterials could also shed light on black holes. In 2008, Leonhardt and his team showed how to mimic an event horizon in the lab.

If the medium through which an electromagnetic wave is propagating is moving as fast as the wave itself, the wave is effectively trapped and cannot escape the medium. This has the same effect as a black hole's event horizon, the point of no return for light: an observer outside an event horizon could see nothing inside, as no light can escape the black hole's gravity to cross the horizon to the universe outside.

To mimic this, Leonhardt's team fired laser pulses into a specially fabricated optical fibre. The pulses were designed to modify the fibre's optical properties, so as the laser pulse travelled along the fibre, the change in the fibre's properties moved along it at the same speed. It was as if a virtual fibre was moving at the speed of light, effectively trapping the light

A black hole emits so-called Hawking radiation, and theory says that Leonhardt's team laboratory analogue should do so too, albeit at levels too small to be easily detected yet. Even Harry Potter's cloak wouldn't be capable of that.

Journal references: The two optical frequency cloak papers: University of California, Berkeley study, Cornell University study; Ergin's 3D cloaking study: Science, DOI: 10.1126/science.1186351; Leonhardt's black hole study: Science, DOI: 10.1126/science.1153625

Extreme PowerPoint places you in 3D slide show

IT WILL either revolutionise your presentations or make "death by PowerPoint" worse. One thing is certain: by allowing you to touch and play with light, Microsoft's LightSpace technology will make presenting more fun.

The LightSpace prototype projects slides, documents, photographs or video onto any surface, from a table to a door. Presenters can then touch and literally pick up a virtual item from a display and carry it across the room as a spot of light in the palm of their hand.

To perform commands – "play video", for example – you move your hand along a projected light beam that acts as the central control. Holding your hand in the right position on the menu for a few seconds activates the function.

"The aim is to bring the kind of multi-touch interaction you get with LCD surface displays to every surface in a room," says Andrew Wilson of the Microsoft Research lab in Redmond, Washington.

On grid

LightSpace works by using projectors, motion-tracking sensors and depth-sensing cameras.

Based loosely on Kinect, Microsoft's gaming system that tracks body movement without the need for a handheld controller, the technology is due to be demonstrated at the User Interface and Software Technology conference in New York City this week.

With Kinect, a device called a "depth camera" bathes the gamer in an infrared grid pattern whose telltale distortion lets a computer work out the distance between a camera and every pixel in the image it observes. That way, it builds a 3D image of the gamer's movements in front of the TV set.

LightSpace uses three depth cameras to create a full 3D image of the area of the room in which a presentation is being made. Instead of looking for gaming cues such as kicks and punches, it identifies which projected media the user is interacting with.

Early stages

It's a compelling prospect, but Microsoft stresses it is still a prototype and far from being out on the market. "We're still exploring the interactions enabled by this kind of technology," says co-developer Hrvoje Benko. For example, it may be most effective when accessed by multiple presenters. In tests the system has successfully tracked six people simultaneously.

Wilson says the project may yet work in concert with another Microsoft project, Skinput, in which a user-worn microprojector casts touchscreen menus on the skin, with taps on the skin recognised acoustically.

If the LightSpace technology does come to market as a presentation tool, users would need to beware of the same issues that spoil so many PowerPoint presentations, says Max Atkinson, author of the book Lend Me Your Ears, a critique of computer-assisted slide-show presentations. He points out that an audience might struggle to concentrate in a presentation with multiple active surfaces. "I'm not against digital aids for presenters, but LightSpace sounds a massive distraction."

The 10 Greatest (Accidental) Inventions of All Time

The Microwave - Percy L. Spencer

Percy Spencer, an engineer at Raytheon after his WWI stint in the Navy, was known as an electronics genius. In 1945, Spencer was fiddling with a microwave-emitting magnetron—used in the guts of radar arrays—when he felt a strange sensation in his pants. A sizzling, even. Spencer paused and found that a chocolate bar in his pocket had started to melt. Figuring that the microwave radiation of the magnetron was to blame (or to credit, as it would turn out), Spencer immediately set out to realize the culinary potential at work. The end result was the microwave oven—savior of eager snackers and single dudes worldwide.

Saccharin - Ira Remsen, Constantin Fahlberg

In 1879, Ira Remsen and Constantin Fahlberg, at work in a laboratory at Johns Hopkins University, paused to eat. Fahlberg had neglected to wash his hands before the meal—which usually leads to a quick death for most chemists, but led to him noticing an oddly sweet flavor during his meal. Artificial sweetener! The duo published their findings together, but it was only Fahlberg's name that made it onto the (incredibly lucrative) patent, now found in pink packets at tables everywhere. That is to say, Remsen got screwed—he later remarked, "Fahlberg is a scoundrel. It nauseates me to hear my name mentioned in the same breath with him."

Slinky - Richard James

In 1943, Navy engineer Richard James was trying to figure out how to use springs to keep the sensitive instruments aboard ships from rocking themselves to death, when he knocked one of his prototypes over. Instead of crashing to the floor, it gracefully sprang downward, and then righted itself. So pointless—so nimble—so slinky. The spring became a goofy toy of many childhoods—that is before every kid inevitably gets theirs all twisted up and ruins it. 300 million sold worldwide!

Play-Doh - Kutol Products

Before being found ground into the rugs of child-rearing homes everywhere, Play-Doh was ironically created to be a cleaning product. The paste was first marketed as a treatment for filthy wallpaper—before the company that produced it began to go down the tubes. The discovery that saved Kutol Products—headed for bankruptcy—wasn't that their wall cleaner worked particularly well, but that schoolchildren were beginning to use it to create Christmas ornaments as arts and crafts projects. By removing the compound's cleanser and adding colors and a fresh scent, Kutol spun their wallpaper saver into one of the most iconic toys of all time—and brought mega-success to a company headed for destruction. Sometimes, you don't even know how brilliant you are until someone notices for you.

Super Glue - Harry Coover

In what have been a very messy moment of discovery in 1942, Dr. Harry Coover of Eastman-Kodak Laboratories found that a substance he created—cyanoacrylate—was a miserable failure. It was not, to his dismay, at all suited for a new precision gun sight as he had hoped—it infuriatingly stuck to everything it touched. So it was forgotten. Six years later, while overseeing an experimental new design for airplane canopies, Coover found himself stuck in the same gooey mess with a familiar foe—cyanacrylate was proving useless as ever. But this time, Coover observed that the stuff formed an incredibly strong bond without needing heat. Coover and his team tinkered with sticking various objects in their lab together, and realized they had finally stumbled upon a use for the maddening goop. Coover slapped a patent on his discovery, and in 1958, a full 16 years after he first got stuck, cyanoacrylate was being sold on shelves.

Teflon - Roy Plunkett

The next time you make a frustration-free omelette, thank chemist Roy Plunkett, whose experienced immense frustration while inadvertently inventing Teflon in 1938. Plunkett had hoped to create a new variety of chlorofluorocarbons (better known as universally-despised CFCs), when he came back to check on his experiment in a refrigeration chamber. When he inspected a canister that was supposed to be full of gas, he found that it appeared to have vanished—leaving behind only a few white flakes. Plunkett was intrigued by these mysterious chemical bits, and began at once to experiment with their properties. The new substance proved to be a fantastic lubricant with an extremely high melting point—perfect at first for military gear, and now the stuff found finely applied across your non-stick cookware.

Bakelite - Leo Baekeland

In 1907, shellac was commonly used to insulate the innards of early electronics—think radios and telephones. This was fine, aside from the fact that shellac is made from Asian beetle poop, and not exactly the cheapest or easiest way to insulate a wire. What Belgian chemist Leo Baekeland found in instead was—get ready—polyoxybenzylmethylenglycolanhydride, the world's first synthetic plastic, commonly known as Bakelite. This pioneering plastic was moldable into virtually any shape, in any color, and could hold its form against high temperatures and daily wear—making it a star among manufacturers, jewelers, and industrial designers.

Pacemaker - Wilson Greatbatch

An assistant professor at the University of Buffalo thought he had ruined his project. Instead of picking a 10,000-ohm resistor out of a box to use on a heart-recording prototype, Wilson Greatbatch took the 1-megaohm variety. The resulting circuit produced a signal that sounded for 1.8 milliseconds, and then paused for a second—a dead ringer for the human heart. Greatbatch realized the precise current could regulate a pulse, overriding the imperfect heartbeat of the ill. Before this point, pacemakers were television-sized, cumbersome things that were temporarily attached to patients from the outside. But now the effect could be achieved with a small circuit, perfect to tuck into someone's chest.

Velcro - George de Mestral

A dog invented velcro.

Alright, that's something of an exaggeration, but a dog did play an instrumental role. Swiss engineer George de Mestral was out for a hunting trip with his pooch, and noticed the annoying tendency of burrs to stick to its fur (and his socks). Later, looking under a microscope, Mestral observed the tiny "hooks" that stuck burrs to fabrics and furs. Mestral experimented for years with a variety of textiles before arriving at the newly invented nylon—though it wasn't until two decades later that NASA's fondness for velcro popularized the tech.

X-Rays - Wilhelm Roentgen

Okay, yes, x-rays are a phenomenon of the natural world, and thus can't be created. But sshhh! The story of their discovery is a fascinating one of incredible chance. In 1895, German physicist Wilhelm Roentgen was performing a routine experiment involving cathode rays, when he noticed that a piece of fluorescent cardboard was lighting up from across the room. A thick screen had been placed between his cathode emitter and the radiated cardboard, proving that particles of light were passing through solid objects. Amazed, Roentgen quickly found that brilliant images could be produced with this incredible radiation—the first of their kind being a skeletal image of his wife's hand.