Flexible, wear-resistant strands of conductive fibers are used to make smart clothing with embedded computers and sensors, such as hats that can sense changes in signals.

Previous efforts to create fibers with wear-resistant coatings and conductive cores have encountered problems. When materials cool and shrink at different rates during manufacturing, or are twisted and cleaned once in the final product, small stress cracks can develop and often cause smart devices to stop working.

now, Rayway Researchers at Singapore's Nanyang Technological University have discovered a conductive material that shrinks on cooling and does not develop stress cracks, similar to the aluminosilicate glass used in smartphone screens. The material borrows techniques from fiber-optic cable manufacturing, and the process is cheap and “industry-ready,” Wei said.

The technique involves placing a semiconductor wire made of silicon or germanium into molten glass at a temperature of about 1000 degrees Celsius and drawing it into thin strands. The glass is later etched away with hydrofluoric acid and replaced with a polymer coating that allows for a more flexible material. Fibers can stretch up to 10 kilometers.

A small amount of this fiber is then woven into fabric using a standard loom and regular cotton. Wei says the new material alone feels like “fishing line” on the skin, so cotton is needed to make the clothes comfortable.

The researchers used the fibers to create several prototypes, including electronic sensors and chips that communicate through conductive materials, such as a hat that detects changes in the color of traffic lights. It then passes that information to a smartphone app, a jumper that can receive and decode images sent by pulses of light rather than radio waves, and a watch strap that measures the wearer's heart rate.

In a six-month test where the garment was worn, washed and dried, the fibers were durable and continued to conduct electricity.

However, there are still weaknesses. The link between the flexible material and the rigid circuit board that holds computer chips and other components tends to fail after a few months, causing smart features to stop working.

“The only part that consistently leads to test failures is the connection between the fiber and the external circuitry,” Wei says. “The challenge now is to find a stable connection method.”