ILED wafers cannot be reused because the normal process is to saw apart the newly formed ILED crystals—while also cutting through the underlying wafer. (OLEDs have always been able to reuse their substrates, one of the reasons they have cost less than ILEDs.) After the ILED crystals have been separated they are picked up by a robotic device so they can be packaged, wired and used as tiles to make jumbotrons and other large, mostly outdoor displays. The robotic device is unable to pick up crystals that are smaller than about 100 microns per side, which prevents ILEDs from being made smaller.
The process that Rogers and his colleagues described in their research uses a different approach to cutting apart and transferring the ILED crystals. "We've found a way to take the inorganic material you grow on the wafer and embed a sacrificial base," he says. The researchers then make a lithographic imprint on the newly formed crystals. Instead of using a saw or a robotic "picker," the researchers use a rubber stamp to separate and lift the individual crystals—which in this new process can be as small as 20 microns on each side—so they can be arranged in tight arrays on glass, plastic, rubber or other surfaces. The underlying wafer can now be reused. (A micron is one millionth of a meter, or about 40 millionths of an inch.)
With this new process, the ILEDs can be interconnected, much the way OLEDs are wired, which saves space. "It's not the individual wiring that's done with ILEDs today," Rogers says.
It's unclear exactly how much of a cost difference there will be between OLEDs and ILEDs if they are used in comparable devices such as televisions or computer monitors. Even though ILEDs cost more to make, Kymissis says, "because they're so bright, you don't need as many."
Ford funded the research in part as a way to develop flexible lighting for vehicle interiors and brake lights, although, according to Rogers, it will be at least a couple of years before his team's technology would be ready for commercial use.