Wearable power weave

Wearable technology is being tailored for the next generation of smart gadgets but one thing that might lead to it unraveling is finding a lightweight and yet efficient way to power wearables. Researchers in the US hope their stitch in time will offer a bespoke answer to the problem. They have developed fabrics that can generate electricity not only from a person's physical movement but also by absorbing energy from sunlight. [Jun Chen et al., Nature Energy (2016); DOI: 10.1038/nenergy.2016.138]

"This hybrid power textile presents a novel solution to charging devices in the field from something as simple as the wind blowing on a sunny day," explains Zhong Lin Wang of the Georgia Tech School of Materials Science and Engineering. Wang and his colleagues used a commercial textile machine to weave together solar cells constructed from lightweight polymer fibers with fiber-based triboelectric nanogenerators. The latter exploits the triboelectric effect together with electrostatic induction to generate a current when the device is rotated, slides or vibrates. The triboelectric nanogenerators trap energy when they become electrically charged in moving contact with a second material. The solar power aspect involves using wiry photoanodes that can be woven into the textile.

Wang points out that the fabric is very flexible, breathable, light weight and could be adapted for use in a wide range of applications, clothing, bedding, curtains, tents. The powerful fabric is just 320 micrometers thin and could be blended with wool or other fibers. "The backbone of the textile is mostly made of commonly used polymer materials that are inexpensive to make and environmentally friendly," Wang adds. "The electrodes are also made through a low-cost process, which makes it possible to use large-scale manufacturing."

In their tests, the team used a small sheet of the powerful fabric attached it to a handling rod to make a small flag, which could blow in the air rushing past their car's open window and generate a significant amount of power even on a cloudy day. Under sunlight and movement, however, the 40 x 50 millimeter piece of fabric could charge a 2 microfarad commercial capacitor to 2 volts in about one minute. "That indicates it has a decent capability of working even in a harsh environment," Wang explains. The next step after proof of principle will be to optimize long-term durability as well as finding a way to encapsulate the electrical components to protect them from rain and moisture.

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".