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 A Thousand Pinpoints of Light

By Phil Berardelli

ScienceNOW Daily News

20 August 2009

Imagine cardboard-thin TV screens that stretch across entire walls or portable video screens that can be rolled up when not in use. Those are some of the possible applications for tiny, inorganic light-emitting diodes (LEDs) that researchers have developed. The new LEDs are just as thin as conventional organic LEDs and liquid-crystal displays, but they're much brighter and more versatile.


That's what a team from institutions in China, Singapore, and the United States set out to do. "We wanted to see if we could use inorganic LEDs in ways that exploit some of the processing advantages of organic LEDs," says materials scientist and co-author John Rogers of the University of Illinois, Urbana-Champaign. The challenge, Rogers explains, was to find a way to grow, shape, and manipulate the inorganic LED devices en masse, because doing so would eliminate the need to cut and connect them individually--a cumbersome task when hundreds or thousands of the devices are involved.

As Rogers and colleagues report tomorrow in Science , they first created what they call a "sacrificial layer" in the manufacturing process. It's a weak adhesive that holds the LEDs in place while they form, but then it's partially dissolved away by an etching liquid. Next, a rubber stamping device presses down on and grabs hold of a bunch of the crystals. The stamping device picks up the LEDs and deposits them onto flexible sheets of glass, plastic, or rubber, where they are integrated with the conductors and insulators that will allow the lighting array to function. The result is a thin, flexible array that's much brighter than conventional organic LED arrays.


Supposedly comparable in price to OLEDs because inorganic diodes are so much brighter, far fewer are needed to create a display of equivalent brightness. This process could give rise to weaving optical electronics into textiles.
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