Spinning a triboelectric yarn

To Georgia Tech’s Zhong Lin Wang, our daily fidgeting, or even tossing and turning in bed at night, is a possible source of renewable energy. Wang’s group has made yarn composed of fabric fibers wrapped around a 50-µm-diameter stainless steel thread that can be woven into brightly colored, washable textiles that generate energy from motion (ACS Nano 2017, DOI: 10.1021/acsnano.7b07534). Sewn into clothing, the textiles could harvest enough energy from walking and everyday activities to charge cell phones and wearable electronics. The yarn is powered by the triboelectric effect, in which static electricity builds up from the friction between two different materials. When the materials move close together, electrons jump from one to the other. When they move back apart, those electrons flow into either a capacitor to store the charge or a circuit to generate power. As the yarn is stretched and released, the outer layer of fabric fibers—made from polyester, cotton, silk, or wool—moves closer to the stainless steel core, then away again, generating a small electric current. The researchers report that a sock with a textile patch charged a capacitor to 1 V after about 19 seconds of walking. The yarn works at up to 90% humidity, so it can survive heavy sweating. It also withstood 120 cycles through a washing machine, but it’s line dry only.