A flexible, durable cloth that generates power from the same effect behind most static electricity could harvest energy from human motion to power wearable gadgets, researchers in Korea and Australia say.
Wearable devices such as the soon-to-drop Apple Watch are growing increasingly popular, but these gizmos are often limited by stiff batteries with limited lives. Although flexible, stretchable batteries do exist, they are often relatively flimsy and have very short battery lifetimes.
The new energy-generating cloth the researchers developed instead aims to power devices using a phenomenon called triboelectricity. When two different materials repeatedly touch and then separate, the surface of one material can steal electrons from the surface of the other. This is why rubbing your feet on a carpet or a comb through your hair can build up static electricity.
The pliable, foldable generators are made from two kinds of fabric — one coated only in silver, and another coated in silver, zinc oxide nanorods roughly 100 nanometers wide and 1 micron high, and silicon rubber. When the researchers stacked four pieces of the cloth together and pushed down, it immediately pumped out 170 volts and 120 microamperes on average and showed a maximum power of roughly 1.1 milliwatts. The cloth was durable as well, generating electricity for more than 12,000 cycles of compression and release.
The researchers showed their nanogenerator could power wearables by embedding six green light-emitting diodes, a liquid crystal display and a vehicle's keyless entry remote control into what they called a "self-powered smart suit," a jacket they stuck their cloth onto. The scientists detailed their findings, which could give new meaning to the term "power suit," online last month in the journal ACS Nano.
Charles Q. Choi is a science reporter who contributes regularly to IEEE Spectrum. He has written for Scientific American, The New York Times, Wired, and Science, among others.