Flexible Micro-LEDs May Reshape Future of Wearable Technology

Researchers from the University of Texas at Dallas and their international colleagues have developed a method to create micro-LEDs that can be folded, twisted, cut, and stuck to different surfaces. The technology aims to fill a demand for bendable, wearable electronics.

“The biggest benefit of this research is that we have created a detachable LED that can be attached to almost anything,” said Moon Kim, the Louis Beecherl Jr. Distinguished Professor, Materials Science and Engineering, at UT Dallas and an 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.”

The researchers developed 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.

The researchers added a nonstick layer to the substrate to make the LED detachable from the wafer. The nonstick layer, made of graphene, acts similarly to the way parchment paper protects a baking sheet and allows for the easy removal of cookies, for example.

“The graphene does not form chemical bonds with the LED material, so it adds a layer that allows us to peel the LEDs from the wafer and stick them to any surface,” Kim said.

Collaborators in South Korea carried out laboratory tests of the LEDs by adhering them to curved surfaces, as well as to materials that were subsequently twisted, bent, and crumpled. In another demonstration, they adhered an LED to the legs of a Lego figure with different leg positions.

Bending and cutting do not affect the quality or electronic properties of the LED, Kim said.

The bendy LEDs have a variety of possible uses, including 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.

The researchers are working to apply the fabrication technique to other types of materials.

The research was published in Science Advances (www.doi.org/10.1126/sciadv.aaz5180).