‘ Yarn batteries’ might power flexible devices

◗ Scientists will need to overcome the challenge of creating a device that is deformable, durable, versatile and wearable while still holding a charge

Beijing, April 1: Scientists have developed rechargeable yarn batteries that are waterproof and flexible, and could power smart fabrics and devices in future.

Most people are familiar with smartwatches, but for wearable electronics to progress, scientists will need to overcome the challenge of creating a device that is deformable, durable, versatile and wearable while still holding and maintaining a charge.

One dimensional fibre or yarn has shown promise, since it is tiny, flexible and lightweight, researchers said.

Previous studies have had some success combining one- dimensional fibres with flexible zinc manganese dioxide batteries, but many of these lose charge capacity and are not rechargeable.

Researchers from University of Hong Kong and Shenzhen University in China wanted to develop a rechargeable yarn zinc- ion battery that would maintain its charge capacity, while being waterproof and flexible.

They twisted carbon nanotube fibres into a yarn, then coated one piece of yarn with zinc to form an anode, and another with magnesium oxide to form a cathode.

These two pieces were then twisted like a double helix and coated with a polyacrylamide electrolyte and encased in silicone.

The study, published in the journal ACS Nano, showed that the yarn zinc- ion battery was stable, had a high charge capacity and was rechargeable and waterproof.

In addition, the material could be knitted and stretched. It also could be cut into several pieces, each of which could power a watch.

In a proof- of- concept demonstration, eight pieces of the cut yarn battery were woven into a long piece that could power a belt containing 100 light emitting diodes ( known as LEDs) and an e l e c t ro l u m i n e s c e n t panel.