Electronicdisplays for integration with clothing and textiles are a rapidly developing field in the realm of wearable electronics. However, flexible LEDs designed to form part of an elastic or deformable coating forclothing or apparel – even displays specifically designed to be directly bio-compatible – still rely on a hard substrate on which to layer theappropriate electroluminescent material. Now researchers at the Korea Advanced Instituteof Science and Technology (KAIST) have created a fiber-like LED thatcan be directly knitted or woven to form part of the fabric itself.

"Ourresearch will become a core technology in developing light emitting diodes onfibers, which are fundamental elements of fabrics," said Professor Choi, headof the research team at the School of Electrical Engineering at KAIST. "We hopewe can lower the barrier of wearable displays entering the market."

The solution-dipping method of LED fiber creation is said to be compatible with processes in the textile industry KAIST

To producetheir LED strands, the scientists start with a fiber of polyethyleneterephthalate, 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 toready it for layering with organic materials. Once dried, the dipped fiber isthen re-dipped in a bath of super-yellow (poly-(p-phenylenevinylene) polymerorganic LED (OLED)) solution, dried again in an oven, and finally coated with a Lithium Fluoride/Aluminum (LiF/Al) compound.

Thisprocess, the researchers claim, is a much more efficient way of applying LEDmaterials to small cylindrical structures than any heat-treating method. By carefullyadjusting the extraction rate of the fiber from the solution, the researcherssay they can control the deposition thickness to within hundreds ofthousandths of a nanometer.

Dipped LED fibers glow brightly when a voltage is applied KAIST

The researchers believe their method of producing LED fibers could be an acceleratorfor the commercialization of wearable displays because inexpensive, automated high-volume production of fibers using such textile manufacturing methods asroll-to-roll processing could be employed. In this way, LED fibers could be mass-produced as easily as nylon or polyethylene fiber is produced today.

"Thistechnology will eventually allow the production of wearable displays to be aseasy as making clothes," said Seon-Il Kwon, a member of the KAIST Electrical Engineeringteam.

The results of this work were recently published in the journal AdvancedElectronic Materials

Source: KAIST