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Fireflies Inspire Brighter LEDs

LEDs are bright, but they don't shine as bright as their potential. That's because when light emits from an LED, some of it gets reflected back inside. 

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To make LEDs brighter, researchers are taking a cue from the firefly. In fireflies, a chemical reaction makes the light, which then emits through the insect’s exoskeleton, called the cuticle. Covering the cuticle are tiny scales that each have jagged edges. Each scale is about 10 micrometers long and makes a little slope that reaches 3 micrometers high. Computer simulations showed that the light at those edges was brighter.

A team of scientists from Belgium, France, and Canada, led by Annick Bay, decided to do something similar with LEDs. They put a layer of light-sensitive material on top of LEDs and then using a laser, created a sawtooth pattern, with each “peak” about 5 microns high. The structure minimized the reflection and boosted the LED's brightness by 55 percent.

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The team isn’t the first to look at fireflies. But previous efforts had focused on the tiniest structures of firefly skin, those at the nanometer scale, comparable to the wavelengths of light. This time, scientists went bigger: they looked at structures that were a thousand times larger.

The papers describing the work appear in the journal Optics Express.

Credit: Optics Express

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Baby Jumper Could Prevent Crib Death

Sudden Infant Death Syndrome is every new parent's worst nightmare. To keep a close eye on a sleeping baby, some parents rely on a two-way baby monitor or move the crib into mommy and daddy's room. Others stay awake all night worrying and periodically checking on their infant.

Researchers at the Fraunhofer Institute for Reliability and Microintegration in Berlin propose a different solution: a suit that monitors a baby's breathing.

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It looks like an ordinary “onesie” or “romper suit” but with a major difference: it has commercially available sensors integrated into the cloth. The circuit board for the sensors is printed on polyurethane, which is flexible, stretchable and comfortable for the child. The polyurethane circuit board is contained in a fabric cover that can be removed so that the jumper can be washed separately. 

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The sensors monitor the movement of the chest and stomach by checking both the distance between two points on the chest and responding to strain. If there is a problem -- if the rhythm of breathing or number of breaths is wrong -- it will sound an alarm. It isn't clear what kind of alarm would sound yet; current proposals are for some kind of visual and auditory alert. It's easy to imagine a wireless system firing off a signal to a smartphone.

The circuits themselves are made of ordinary materials and don’t need any specialized manufacturing methods, so the costs can be kept down. Since the electronics are mounted on the polyurethane sheets  rather than being stitched into the fabric, it’s easier to place the components exactly where they need to be on the circuit board.

The idea is similar the Exmobaby suit that appeared early in 2012. The difference is the use of flexible electronics and that the Exmobaby’s ad copy says it’s designed to track emotional states, not operate as a true medical device.

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There are still challenges to mass-producing the suit. One is that polyurethane tends to change shape during the manufacturing process. Even so a number of companies are testing out ways to build them cheaply. 

Baby safety isn’t the only idea the Fraunhofer scientists came up with for their flexible electronics: they also looked at how to make pressure bandages that tell doctors and nurses where the best place to put them is, and even a bandage that can monitor the health of kidneys.

Via Fraunhofer Institute

Credit: Fraunhofer Institute / VERHAERT Masters in Innovation

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Light Powers Levitating Magnets

Magnetic levitation is old hat these days, with maglev trains operating in China and planned systems taking shape in other countries. But they run by manipulating the train, which is "floating" on a magnetic field, with electricity. Now a team of researchers in Japan have found a way to manipulate magnetically levitating objects using light. The technique could lead to new forms of powered maglev transportation systems and could make solar-powered generators more efficient.

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To make the levitating graphite device, Masayuki Kobayashi and professor Jiro Abe of Aoyama Gakuin University in Kanagawa arranged a set of magnets made of neodymium, iron and boron in a grid. They then put a piece of graphite on top of the grid. When exposed to an external magnetic field, graphite -- specifically an artificial type called pyrolitic graphite -- generates its own field that repels the external one, a property called diamagnetism. That makes graphite levitate when it's placed on top of permanent magnets.

The researchers then hit the graphite with a laser. The laser heated up part of the graphite and changed its susceptibility to the surrounding magnetic field. Hitting the graphite in the center made it sink, as the heating was more even. Aiming the laser at the edge made it move in the direction of the beam.

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Next, they put the graphite on top of a tower of cylindrical magnets and hit the edge of it with the laser beam. The result was a little graphite disc spinning at up to 200 rpm when it was exposed to the laser -- or sunlight.

The researchers published the results of their study in the Journal of the American Chemical Society.

Being able to generate useful mechanical motion this way could change the way solar power setups are made. A spinning disk could run a generator directly rather than extracting the energy in several steps such as converting the DC current from a photovoltaic cell or using solar power to make steam.

Via Physorg, Journal of the American Chemical Society

Credit: Masayuki Kobayashi and Jiro Abe

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Gel and Light Beam Could Starve Tumors

A gel that expands and contracts when hit with light could work to cut off the blood supply to a tumor.

Developed by Akira Harada, a professor of Macromolecular Science and his team at Osaka University in Japan, the gel could also be used inside a person's body to pump drugs in a specific location at a specific time.

The gel is made from a polymer called a hydrogel and two chemicals -- alpha-cyclodextrin and azobenzene -- that work similar to muscle-contracting enzymes in the body. When exposed to ultraviolet light, the gel expands. When exposed to red light, it contracts.

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Hitting a strip of the gel with UV light from different directions makes it bend away from the light. "Only the surface irradiated by UV absorbs the light, while the other side does not," Harada told Discovery News. "Therefore, the [strip of] gel bends. The same is true for irradiation by visible light." After exposure to UV light for 15 minutes, the gel formed curly shapes like spirals.

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The gel expands and contracts because of the way the two added chemicals change when the light hits them. When inside the gel, the cyclodextrin and azobenzene molecules are bound to each other and molecules that make up the gel. Ultraviolet light disturbs those bonds and changes the shape of the azobenzene molecule. The azobenzene breaks from the cyclodextrin. This allows the gel molecules to spread out, expanding the volume. Red light restores the molecules' original shapes, which makes them bind tightly again, which shrinks the gel.

Harada said that he was able to repeat the expansion and contraction at least five times without the gel losing its ability to do it, and there's no reason it couldn't continue.

Using the light to alter the chemical bonds and change the shape of the gel is new, said Albert Schenning, an associate professor of chemistry at the Eindhoven University of Technology in the Netherlands.

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Using the gel in a medical situation might involve a doctor injecting the gel into a vein and then running an very thin optical fiber to the location to deliver the light. A gel laced with drugs would theoretically release them at the sight as it expanded. Or it could be expanded inside a blood vessel feeding a tumor to cut off the supply.

There is still some work to do. The reaction is still slow -- to get the gel to expand or contract took an hour. Schenning said future experiments might show how to speed that up.

Harada's work appears in the Dec. 11 edition of Nature Communications.

Photo: Blood vessels feed cancer cells, but a new technique could choke those vessels off and stop cancerous growth. Credit: Sciepro/Science Photo Library/Corbis

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Next Gen Power Suits Woven from Silicon Fiber

In the future, power suits may do more than command attention and exude confidence. They may actually charge your electronic devices.

A team of scientists led by John Badding, a chemistry professor at Pennsylvania State University has made a solar cell into the shape of a fiber, which can be woven into fabric. That fabric could be turned into a garment that harnesses energy from the sun and turns it into renewable electricity.

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The researchers combined glass optical fibers with traditional photovoltaics normally used for rooftop solar panels. Both of these components are typically rigid and stiff. But Pier Sazio, a research fellow in optoelectronics at the University of Southampton and one of the co-authors, told Discovery News that silicon becomes flexible when it's very thin, while also retaining its strength. 

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To make the fiber, they mixed silicon with other elements, including boron and helium and then turned it into a hot, high-pressure gas. Next, they filled a thin, hollow fiber optic with the gas mixture. As it cooled, the silicon mixture formed three concentric layers.

The innermost layer, called the "p" layer, was positively charged and accepted electrons. The outermost layer, called the "n" layer, was negatively charged and had an excess of electrons. A middle layer between the two, called the "i" layer, was neutral.

As sunlight hits the fiber, photons knock electrons from the outermost "n" layer and send them into the "p" layer. That generates current, just like an ordinary solar celm, except this one is cylindrical rather than flat.

By attaching two small electrodes, one to the "p" layer and the other on the "n" layer, one would be able to extract the charge for power.

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Because the fiber is round, it's able to pick up sunlight from any angle. The thinness of the fiber -- on the order of 15 micrometers, which is about the same as acrylic -- allows it to be woven and twisted and turned into clothing that could power or charge a small electronic device. No surprisingly, the military has been interested: modern soldiers carry a lot of electronic gear and batteries are heavy.

The work appeared online on Dec. 4 and wil be in an upcoming print issue of Advanced Materials.

via Penn State, Advanced Materials

Credit: Badding, et. al, Pennsylvania State University

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Mysterious Material Remembers Its Shape

By TechNewsDaily Staff

A weird new lab-made substance acts like a liquid in air, but is solid in water. Credit: Luo Lab

A strange new substance acts like a liquid when exposed to air, but takes a solid shape when it's dunked in water.

The new stuff is a metamaterial, scientists' word for a lab-made material that has properties uncommon in nature. Even among metamaterials, however, this material is unusual -- it's composed of artificial DNA, while most metamaterials are composed of nonbiological chemicals such as silicon or copper. Its creators are calling it a "meta-hydrogel."

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In the future, metamaterials made of biological stuff could go into soft, flexible circuits, according to a statement from Cornell University, where the meta-hydrogel was made. Because they have pores in which drug molecules could fit, meta-hydrogels could help release medicines slowly inside the body, the statement said.  

Adding to its unusual properties, the new meta-hydrogel remembers its original shape. If it's made in a mold, it will return to its original, molded shape every time it's doused in water, even after researchers expose it to air -- and force it into its liquidlike state -- several times. The researchers made a video that shows the meta-hydrogel firming up into letters when a researcher adds water to it.

To get the meta-hydrogel to take on a new solid shape, the gel’s creators heat it to 185 degrees Fahrenheit (85 degrees Celsius) and set it in new molds.

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When a team of Cornell engineers first mixed the chemicals to make their meta-hydrogel, they didn't know it would act so strangely. "This was not by design," Dan Luo, the lead scientist in the research, said. Luo and his colleagues have used synthetic DNA to make hydrogels, or gels composed mostly of water, before. This time, they wanted to make a DNA hydrogel with a different microscopic structure. It was only after they created their meta-hydrogel that they discovered its unique abilities, the researchers wrote in a paper they published Dec. 2 in the journal Nature Nanotechnology.

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Copyright 2012 TechNewsDaily, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Plastic Could (Finally) Replace Glass

Everyone loves a good touch screen -- until it drops and gets cracked. The only other material that was feasible for them was plastic, but there wasn’t one that was strong and hard enough, until now.

Dai Nippon Printing, of Japan, unveiled a plastic that resists scratching as well as glass does and has the added bonus of being flexible. It would replace the glass covers that currently grace the fronts of smartphones.

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The display cover is actually comprised of separate layers: one is the resin that gives the display cover its hardness, while the other protects it from fingerprints. The company didn’t go into details about the composition of the plastic in its press release.

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How hard is the display? According to the company it has a “pencil hardness” of 9H, which means that a 9H pencil has a tough time scratching it; that’s comparable to many ceramics and enamels.

DNP also tested steel wool on it with a pressure of 7 pounds per square inch (500 grams per square centimeter) and found it still didn’t scratch after 200 scrapes.

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Hardness is only one part of it, though. The fact that it's plastic means that it's slightly flexible, and that in turn means it won’t shatter when dropped. Any smartphone  owner will appreciate that. Plastic is also lighter than the same volume of glass.

On top of all that, the flexibility allows a bendy display.

DNP has said they will be shipping samples in the first part of 2013, so it isn’t clear if any smartphone makers have signed on. But anything that makes un-crackable touch screens is a welcome development for the butterfingered among us.

Credit: Dai Nippon Printing

Via TechOn, Dai Nippon Printing (In Japanese)

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Coated Sapphire Is Invisible to Infrared Cameras

Infrared detectors are used to see objects otherwise hidden under cover of darkness. The dectors pick up the heat given off by living bodies, warm buildings and vehicles and reveal them as glowing objects when viewed through infrared goggles or cameras. If a building, body or vehicle is cold, the detector typically can't visualize it.

Now new technology from researchers at Harvard School of Engineering and Applied Sciences could turn infrared detection on its head. The technique not only makes hot objects appear cold to infrared detectors -- which could help hide soliders from their enemies at night -- but it can be also used to make an infrared camera so sensitive that even cold objects would look relatively bright.

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The researchers coated a millimeter-thick sheet of sapphire with a 180-nanometer layer of vanadium dioxide, which is used as an insulator. Next, they heated the layered material to 154 degrees Fahrenheit (68 degrees Celsius). At that temperature, the crystal structure of the vanadium dioxide became altered, changing it from an insulator to a metallic conductor.

When the scientists shone infrared light onto the altered material, they found it was a near-perfect absorber, soaking up 99 percent of the infrared light that hit it. It worked because the infrared light waves bounced off the sapphire get absorbed by the vanadium dioxide, and any light waves that escape destructively interfere with each other so that they cancel out.

When the scientists cooled the layers down, the materials returned to their former states.

Mikhail Kats, the lead author of the research, told Discovery News that vanadium dioxide, unlike other materials, absorbs infrared radiation differently depending on its temperature -- it can be tuned.

If one could coat a vehicle or building with this material, it would make the objects invisible -- or at least black -- to an infrared camera, since any infrared radiation emitted by the objects would be absorbed by the material before it could escape.

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And because the material is so sensitive to infrared light, it could also work as a detector. Any imaging device has to absorb light in order to translate it into electrical signals and make a picture. The more sensitive the sensor, the better the detector.

One big challenge was making the vanadium dioxide crystals pure enough. Any flaws would mean it lost its unique reaction to temperature.

The research appears in the latest issue of Applied Physics Letters.

via Harvard University

Credit: Harvard University / Kirill Nadtochiy

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Japanese Floating Train of the Future Has Arrived

Just when you weren't sure whether Japanese trains could get any faster or more convenient, the Central Japan Railway Company unveils the prototype for a floating maglev train designed to hit 311 miles per hour.

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Granted the train isn't scheduled for use until, oh, 2027, but the specs are impressive. The train manufacturer, known as JR Tokai for short, recently showed the public its "Series L0" prototype. With a 92-foot-long front car and a lengthy aerodynamic nose, the 14-carriage train will float above the tracks.

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This frictionless train will use magnetic levitation -- maglev -- to take passengers from central Tokyo to the western city Nagoya in about 40 minutes. For a bullet train, that trip currently takes closer to 90 minutes. By car, the distance between the two cities is a little over 200 miles.

Magnetic levitation promises insanely smooth, quiet and high-speed transportation. But, as Gizmodo's Andrew Tarantola rightfully pointed out, maglev trains are far more expensive and technically challenging to build. This particular project will ultimately cost a mind-boggling $112 billion, Engadget's Nicole Lee reported. For perspective, Boston's Big Dig project cost $24.3 billion, including interest.

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Once the Tokyo-Nagoya leg is completed, the plan is to extend it to Osaka by 2045. Maybe at that point Japanese train prototypes will just be teleporting passengers. A girl can dream, right?

Photo: Central Japan Railway Company's Series L0 prototype is designed to travel at 311 miles per hour. Credit: Phys.org.

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Solar 'Funnel' Could Boost Energy Efficiency

Typical solar cells made of silicon miss out on a wide swath of energy shining from the sun.

But according to calculations made by scientists at the Massachusetts Institute of Technology and China's Peking University and Xi'an Jiaotong University, poking a sheet of material just a molecule thin changes the material's atomic structure and improves its ability to harvest a broader spectrum of sunlight.

Conventional solar panels made of crystalline silicon are most sensitive to wavelengths of sunlight in the red end of the visible range or the near-infrared. Panels made of amorphous silicon are more sensitive to wavelengths of light in the blue range.

But the sun's peak wavelength is in the green part of the spectrum. Photons (light particles) from that wavelength of light do the best job at hitting atoms inside solar panels and knocking out the electrons that ultimately generate an electric current. If solar panels could be tuned to harvest a larger spectrum of sunlight, they'd generate more electricity and be more efficient.

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In this week's issue Nature Photonics, MIT professor Ji Lu and his colleagues have proposed a radical idea that turns a very thin sheet of material into a kind of “solar energy funnel” that takes advantage of elastic strain. The material is molybdenum disulfide, which is not typically made into a solar panel but has been experimented with as a semiconductor material for transistors. It's also in a certain class of substances called 'ultrastrength materials,' which can be stretched out of shape for long periods of time without breaking.

The technique involves poking the sheet of molybdenum disulfide with a microscopic needle. The pressure from the needle causes an elastic strain that not only takes on the shape of a funnel but increases in intensity toward the center.

Like silicon, molybdenum disulfide releases electrons when hit by sunlight. Stretching the material into a funnel shape varies its atomic structure from the edge to the center, and allows different parts of the sheet to respond to photons from different wavelengths of sunlight.

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This means a single sheet of material can actually work harder to collect more energy from the sun. In addition, because the sheet is funnel-shaped, the charged particles will tend to gather at the bottom of it -- moved there by electrostatic energy and not gravity. Having the electric charges all end up in one place is a lot more efficient than having them simply bouncing randomly around the sheet.

All this sounds good, but it hasn't been confirmed by real-world experiments; the calculations are all mathematical models. But the principle has been used before. IBM and Intel have both done experiments with elastic strains in silicon channels in transistors with some success.

Via MIT News

Credit: MIT News/ Yan Liang

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