Nano-bristle clothes to generate power from body motions

We wrote the other day about a power-generating knee-brace. Here is an intriguing energy-producing innovation: Piezoelectric fabric which generates power through the bending of its component threads. The idea is to harvest useful amounts of power from a wearer’s body motions. In 2007 Zhong Lin Wang, a materials scientist at the Georgia Institute of Technology in Atlanta developed a generator composed of a forest of piezoelectric zinc oxide nanowires topped by a flat conductive plate. As the plate is pushed down, the wires bend, producing a voltage that induces current to flow into the plate. The New Scientistreports that now Wang has turned this idea into an electricity-generating thread, which he plans to weave into a fabric. His team figured out how to grow the nanowires on a strand of Kevlar fibre instead of a flat surface, so that the wires stick out from the fiber like the bristles on a pipe-cleaner. When two of the bristly fibers rub against one another, the nanowires deform, causing a current to flow through a thin layer of metal coating on one of the fibers.

In tests with just two short fibers, Wang’s team was able to generate a few picowatts of power, but they found that the power output increased fifty-fold when three pairs of fibers are twined together into a yarn, increasing the area of contact. Wang estimates that the fabric should be capable of generating about 80 milliwatts of electricity per square meter, enough to charge a cellphone battery or other personal electronics from the ordinary motions of a shirt or a curtain blowing in the wind. A fabric woven from such coated fibers should not ultimately be too expensive either, he adds, because the nanowires can be grown in bulk. With the fibers just forty micrometres in diameter, bristles and all, they should be much too small to give the wearer any prickly discomfort.