These "Hair-Thin" Semiconductor Fibers Drive Smart Hats, Shirts, and Watch Straps

Researchers from Nanyang Technological University and the Chinese Academy of Sciences have developed "hair-thin" semiconductor fibers that, they say, can be woven into almost any fabric to create smart wearable electronics.

"It took extensive analysis before landing on the right combination of materials and process to develop our fibers," claims Wan Zhixun, first author on the paper detailing the team's work. "By exploiting the different melting points and thermal expansion rates of our chosen materials, we successfully pulled the semiconductor materials into long threads as they entered and exited the heating furnace while avoiding defects."

The fibers themselves are made from a silicon semiconductor core with a silica glass tube, and a germanium core with an aluminosilicate glass tube — all common materials. The silicon version, the researchers say, is well suited to extreme conditions; the germanium version capable of working with light-based technologies, including Li-Fi networks. The cores are inserted into the glass tubes and heated, then stretched through an extruder. Once stretched, the glass is removed and the core combined with a softer polymer tube and metal wires — then heated and pulled again to create the final, hair-thin soft threads.

"Silicon and germanium are two widely used semiconductors which are usually considered highly brittle and prone to fracture," says Gao Huajian, professor and co-principal investigator on the project. "The fabrication of ultra-long semiconductor fiber demonstrates the possibility and feasibility of making flexible components using silicon and germanium, providing extensive space for the development of flexible wearable devices of various forms."

To prove the concept, the team has woven the fibers into a trio of wearable electronics: a beanie hat that can receive signals from traffic lights to assist with crossing the road; a "smart top" shirt designed to be worn at art galleries and museums to receive information about exhibits and feed it to the wearer's earpiece; and a smartwatch wristband that uses the fibers to measure heart rate without a rigid sensor.

The team's work has been published under open-access terms in the journal Nature.