Aug. 21, 2009 -- Bend it, twist it, roll it or stretch it, a new light emitting diode, or LED, created by scientists will still light up.
The new flexible and stretchable LEDs could be used in everything from bumper mounted brake lights to computer and television screens that roll up into a pen.
"These new inorganic LEDs are so thin you can roll them up, bend them over, and it doesn't affect their operation at all," said John Rogers, a scientist at University of Illinois at Urbana-Champaign and co-author of the paper that appears in this week's issue of the journal Science.
The two varieties of LEDs, organic and inorganic, appear on on everything from billboards to cell phones.
Organic or carbon-based LEDs are generally smaller and easier to manufacture, which is why they appear on cell phone screens. In general, inorganic LEDs are more difficult to create, needing higher temperatures and harder surfaces.
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Inorganic LEDs, however, tend to have higher performance than their organic counterparts. Inorganic LEDs are generally brighter and more efficient, which is why they are typically used in traffic lights, flashlights and outdoor electronic billboards.
"Think about a big billboard display made of (inorganic) LEDs," said Rodgers. "You can see the image clearly on a sunny day, but if you get close, you realize the individual LEDs are large and rather clunky."
The new inorganic LEDs don't have that issue. In fact, at 20 microns across and two microns tall, they are smaller than a 50 micron diameter human hair. Using commercially available printing technology, scientists say the LEDs could shrink to five microns across.
That tiny size gives the LEDs a flexibility and stretchability that no inorganic LED has ever achieved.
The scientists created the super skinny LEDs by same way LEDs have been manufactured for years, but with one change. Starting with a wafer, the scientists deposited the light emitting materials onto the hard surface. Between the LED layers and the wafer the scientists inserted a "sacrificial layer," according to Rogers.
The wafer template, which is usually destroyed in the process, can then be reused, which should make cheaper inorganic LEDs to manufacture.
The middle, sacrificial layer can be dissolved away and the LED lifted off with a rubber stamp and deposited on plastic, rubber or glass substrates.
"The fact that they can put the LEDs on almost any substrate is very exciting," said Ali Javey, a professor of electrical engineering at the University of California, Berkeley.
"This technology is probably scalable (to mass production). It needs to be demonstrated, but I don't see any show-stoppers in that regard."
One of the first uses of the material could be as a brake light in car bumpers. Part of the funding for the research came from car manufacturer Ford to develop a flexible red inorganic LED.
The Science paper only details red inorganic LEDs, but Rogers said he has unpublished data where he has produced blue, white, infrared and other colored inorganic LEDs.
There are a multitude of other potential applications for flexible and colored LED. Televisions, roll-up computer screens, light emitting elastic headbands and much more could be possible during the next few years, according to Rogers.
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