A piezoelectric fabric that generates power through the bending of its component threads could 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, US, 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.
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 fibre like the bristles on a pipe-cleaner.
When two of the bristly fibres rub against one another, the nanowires deform, causing a current to flow through a thin layer of metal coating on one of the fibres.
In tests with just two short fibres, Wang's team was able to generate a few picowatts of power, but they found that the power output increased 50-fold when three pairs of fibres 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 metre, enough to charge a cellphone battery or other personal electronics from the ordinary motions of a shirt or a curtain blowing in the wind.....