Archive for August 5th, 2009
LED Lights That Fit in Your Wallet: The Next Big Thing?
Pretty soon, you may be lighting up your office or home with a flat, credit-card sized LED light. Oree, an Israeli start-up, recently received $4 million in funding from Silicon Valley Bank and Kreos Capital to work on driving down the cost of LED lighting.
According to Oree, small, flat lights emit less heat and consume less energy than standard LED bulbs. The lights could be used in everything from LCD displays to offices that require discreet lighting.
Oree’s flat LED’s can also be molded into shapes—a quality that could reduce the production cost of electronics using the technology.
Other companies working on lowering the cost of LED include Illumitex, Lumenz, and Bridgelux.
Oree’s announcement is part of a larger Israeli trend—the country has attracted $400 million in cleantech investments in the last few years.
Interested in making your own? Click here for the Video
Nitride phosphor from Philips Lumileds closes yellow LED gap
Posted by LED Larry in Uncategorized on August 5th, 2009
Philips Lumileds researchers have developed a monochromatic nitride diode that closes the yellow light LED gap.
The phosphor-converted (PC) amber LED demonstrated by Regina Mueller-Mach and her colleagues uses the down-conversion of blue light from an indium-gallium-nitride (InGaN) LED to longer-wavelength light by a phosphor, in a variation of a well-established process for producing cold or warm white light from blue LED light.
Monochromatic LEDs cover a large part of the visible spectrum with high efficiency. For blue light, nitride diodes achieve external quantum efficiencies in excess of 65%.
For red light, phosphor diodes achieve efficiencies of approximately 50%. However, so far no highly efficient monochromatic LEDs have been available for the “yellow gap” at around 560 nm.
Leveraging previous research on warm white light, the researchers succeeded in down-converting blue LED light into monochromatic amber light with a 595 nm wavelength and a color purity of 98.7%. The external quantum efficiency of the PC amber LED is at 30-40%, depending on temperature.
Compared to direct amber LEDs, the new PC amber LED is two to five times as bright. It achieves a light output of 70 lumens at a 350 mA current.
The LUXEON Rebel PC Amber LED can be used in yellow traffic lights or signals as well as in cars’ turn signals or warning lights for construction sites, or in consumer electronics because their high efficiency makes them relatively inexpensive.
–Posted by Gail Overton from Laser Focus World
Filmmaker takes a new look at the world through Eyeborg project
Eyeborg Projects
After years of wearing a patch to hide his disfigured right eye, damaged as a child in a shooting accident, Canadian filmmaker Rob Spence was forced eventually to replace the eye with a prosthetic one. The camera on Spence’s cell phone, though, gave him a rather novel idea. What if he could build a miniature, wireless video camera into his prosthetic eye? What followed has become the Eyeborg Project, the progress of which can be now followed online.
While Spence had few resources of his own to invest, the sheer inventiveness of the project has attracted backing from many quarters, including corporate circles. Also assisting Spence is engineer Kosta Grammatis and inventor and professor Steve Mann – aka Cyber-Mann – who has worn video-enabled computers since the early 1980s.
While Spence’s project initially drew comparisons with the bionic eye featured in the ‘70s TV show, The Six Million Dollar Man, recent attempts to fit a working LED device into his eye socket, as reported by New Scientist, gives Spence an appearance more like that of Arnold Schwarzenegger’s cyborg from Terminator.
Although this development is more of a sideshow to the main event: installing a video camera with which Spence can capture his unique perspective on the world around him – a take that, if all goes according to plan, will be relayed back to a computer.
In recent months, the Eyeborg team is reporting “major headway” and hopes to have a working prototype up and running later this month. Stay tuned.
Making Light Bulbs from DNA
DNA light: Coating an ultraviolet LED with DNA nanofibers containing dyes creates a bulb that emits bright white light. Credit: Angewandte Chemie
By adding fluorescent dyes to DNA and then spinning the DNA strands into nanofibers, researchers at the University of Connecticut have made a new material that emits bright white light. The material absorbs energy from ultraviolet light and gives off different colors of light–from blue to orange to white–depending on the proportions of dye it contains.
The researchers, led by chemistry professor Gregory Sotzing, create white-light-emitting devices by coating ultraviolet (UV) light-emitting diodes (LEDs) with the material. They are even able to fine-tune the white color tone to make it warm or cold, as they report in a paper published online in the journal Angewandte Chemie.
The new material could be used to make a novel type of organic light bulb. The light emitters should also be longer-lasting because DNA is a very strong polymer, Sotzing says. “It’s well beyond other polymers [in strength],” he notes, adding that it lasts 50 times longer than acrylic.
The color-tunable DNA material relies on an energy-transfer mechanism between two different fluorescent dyes. The key is to keep the dye molecules separated at a distance of 2 to 10 nanometers from each other. When UV light is shined on the material, one dye absorbs the energy and produces blue light. If the other dye molecule is at the right distance, it will absorb part of that blue-light energy and emit orange light.
By changing the ratio of the two dyes, the researchers can alter the combined color of light that the material gives off. Varying the amount of dye also lets them make finer tweaks. For example, by increasing the proportion of dye in the DNA from 1.33 percent to 10 percent, they can change the white light from cool to warm. “As you go across the white spectrum, if you want a soft yellow-type light or blue-type light, you can get these very easily with the DNA system,” Sotzing says.
Others have used nanostructured materials such as silica nanoparticles and block copolymers–self-assembled materials containing two linked polymer chains–to get the right spacing between the two dyes. But, says David Walt, a chemistry professor at Tufts University, “the advantage in the present system seems to be that the DNA fibers orient the dyes in an optimum way for efficient [fluorescence energy transfer] to occur.” Furthermore, when larger amounts of dye are used in the other materials, they start to aggregate. This has two effects: it decreases energy transfer between them, dimming the light output, and it also prevents precise color tuning.
To make the fibers, Sotzing and his colleagues make a solution of salmon DNA and mix in the two types of dye. The solution is pumped slowly out from a fine needle, and a voltage is applied between the needle tip and a grounded copper plate covered with a glass slide. As the liquid jet comes out, it dries and forms long nanofibers that are deposited on the glass slide as a mat. The researchers then spin this nanofiber mat directly on the surface of an ultraviolet LED to make a white-light emitter.
During the fiber-spinning process, the two different dye molecules automatically attach themselves to two different locations on the DNA. The researchers have found in previous work that the nanofiber mats produce 10 times brighter light than thin films of the dye-containing DNA.
“It’s really very cool [work], and I think that it has practical promise,” says Aaron Clapp, a professor of chemical and biological engineering at Iowa State University. “[But] it seems like an overly dramatic way of doing it.”
Clapp speculates that instead of relying on energy transfer between the two fluorescent dyes, you could just change their ratios and get the colors you want.
However, each dye would then require a different input energy source as opposed to just one UV source, Sotzing points out. What’s more, energy transfer between two dyes gives better control over the color of the output light.
Walt says that it may be possible to use the first dye to transfer energy to multiple dyes and get an even wider range of colors. “The results reported here suggest DNA-[energy transfer] light emitters are promising,” Walt says, “but the ultimate utility will depend on factors such as lifetime and power efficiency.”
Copyright Technology Review 2009.