Researchers at UT Dallas and their international colleagues have developed a method to create micro LEDs that can be folded, twisted, cut and stuck to different surfaces. Their invention helps pave the way for the next generation of flexible, wearable technology.
As they are lightweight, thin, energy-efficient, and visible in different types of lighting, LEDs are ideal components for backlighting and displays in electronic devices. They are typically used in products ranging from brake lights to billboards, reports UT Dallas.
Micro LEDs can be as small as 2 micrometers and bundled to be any size. They provide higher resolution than other LEDs. Their size makes them a good fit for small devices such as smartwatches, but they can be bundled to work in flat-screen TVs and other larger displays. LEDs of all sizes, however, are brittle and typically can only be used on flat surfaces.
“The biggest benefit of this research is that we have created a detachable LED that can be attached to almost anything,” said Dr. Moon Kim, Louis Beecherl Jr. Distinguished Professor of materials science and engineering at UT Dallas and a corresponding author of the study. “You can transfer it onto your clothing or even rubber — that was the main idea. It can survive even if you wrinkle it. If you cut it, you can use half of the LED.”
Researchers in the Erik Jonsson School of Engineering and Computer Science and the School of Natural Sciences and Mathematics helped develop the flexible LED through a technique called remote epitaxy, which involves growing a thin layer of LED crystals on the surface of a sapphire crystal wafer, or substrate.
Typically, the LED would remain on the wafer. The researchers added a layer, made of a one-atom-thick sheet of carbon called graphene, to prevent the new layer of LED crystals from sticking to the wafer.
Their colleagues in South Korea carried out laboratory tests of LEDs by adhering them to curved surfaces, as well as to materials that were subsequently twisted, bent and crumpled. They also adhered an LED to the legs of a Lego minifigure with different leg positions.
The flexible, bendable LEDs have potential uses in flexible lighting, clothing and wearable biomedical devices. From a manufacturing perspective, the fabrication technique offers another advantage: Because the LED can be removed without breaking the underlying wafer substrate, the wafer can be used repeatedly.
“You can use one substrate many times, and it will have the same functionality,” Kim said.
The research was published online in the journal Science Advances.