CORK, Ireland--William Henry, an applications specialist at Ireland's Tyndall National Institute, can't tell you exactly how long one of the miniature LEDs the organization has developed will emit light. But it's a long time.
The micro LED--which is significantly smaller than conventional light-emitting diodes--requires only a few billionths of an amp to operate. Thus, it can survive for quite a while on a limited power source. One of the researchers on the project had one running constantly for two-and-a-half years on his desk. Then someone damaged it while moving it around. One member of the group calculated that it could last 80 years (assuming no accidents) on the power stored in a coin-size battery.
"We can produce visible light from nanoamps," Henry said.
Miniature is the keyword in the FLAME project, which stands for "future lighting applications for miniature entities." The micro LED measures only 15 microns across, far smaller than the 300 microns of a conventional LED. (A micron is a millionth of a meter).
Smaller devices generally consume less power than larger ones. The device is also more efficient at extracting light from the power put into it than standard LEDs, which means that it also emits less heat. Although the light from LEDs tends to be cool, the back of diodes, which are chips, do get hot. Venture capitalists have been showering the LED industry with investments in the past few years because many believe the chips will replace conventional lights.
Tyndall will initially likely try to market the device as an alternative to lasers, particularly in medical equipment. Lasers are far from perfect. They wear out, they create safety problems for people handling them, and they can also produce heat, a problem when you are trying to harvest or examine fluid or tissue samples from a patient. By contrast, these micro LEDs could be placed at the tip of fiber-optic probes or used inside chips designed for examining blood samples without changing the state of the materials it is studying.
The small size could also open the door to some commercial applications. One idea floating around the lab is to embed these tiny devices into shoes or tickets to prevent counterfeiting. (Pink Floyd put an LED in a CD case once. It flickered on every few seconds to remind you that you own it.)
I asked if I could take a picture of one of the prototypes; instead, I received the official photograph of some of the pixels. A while back, the institute obtained a fancy camera to shoot a picture of a micro LED while it was turned off, but in all of the close-ups it got washed out in the background when it wasn't emitting light. Eventually, they just put it under a microscope and got the image from there.