Researchers from the School of Electrical Engineering at KAIST have developed fiber-like light-emitting diodes (LEDs), which can be applied in wearable displays.

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Traditional wearable displays have been manufactured using a hard substrate, which is subsequently attached to the surface of clothes. The technique has had limited applications for wearable displays because they were inflexible and ignored the characteristics of fabric.

To solve the problem, the research team, led by Professor Kyung-Cheol Choi, discarded the notion of creating light-emitting diode displays on a plane. Instead, they focused on fibers, a component of fabrics, and developed a fiber-like LED that shared the characteristics of both fabrics and displays.

The technology applies a dip-coating process to immerse and extract a three dimensional (3-D) rod (a polyethylene terephthalate fiber) from a solution, which functions like thread. Then, the regular levels of organic materials are formed as layers on the thread.

The dip-coating process allows the layers of organic materials to be easily created on the fibers with a 3-D cylindrical structure, which had been difficult in existing processes such as heat-coating process. By controlling of the withdrawal rate of the fiber, the coating's thickness can also be adjusted to the hundreds of thousandths of a nanometer.

The researchers said that the technology would accelerate the commercialization of fiber-based wearable displays because it offers low-cost mass production using roll-to-roll processing, a technology applied to create electronic devices on a roll of flexible plastics or metal foils.

“Our research will become a core technology in developing light emitting diodes on fibers, which are fundamental elements of fabrics. We hope we
can lower the barrier of wearable displays entering the market,” said Professor Choi.