However, flexible LEDsdesigned to form part of an elastic or deformable coating for clothing or apparel – even displays specifically designed to be directly bio-compatible – still rely on a hard substrate on which to layer the appropriate electroluminescent material. Now researchers at the Korea Advanced Institute of Science and Technology (KAIST) have created a fiber-like LED that can be directly knitted or woven to form part of the fabric itself.
"Our research will become a core technology in developing light emitting diodes on fibers, which are fundamental elements of fabrics," said Professor Choi, head of the research team at the School of Electrical Engineering at KAIST. "We hope we can lower the barrier of wearable displays entering the market."
To produce their LED strands, the scientists start with a fiber of polyethylene terephthalate, which they then dip several times into a solution of PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) and then dry at 130° C (266° F) for 30 minutes to ready it for layering with organic materials. Once dried, the dipped fiber is then re-dipped in a bath of super-yellow (poly-(p-phenylenevinylene) polymer organic LED (OLED)) solution, dried again in an oven, and finally coated with a Lithium Fluoride/Aluminum (LiF/Al) compound.