When a zinc oxide nanowire is stretched or compressed, a voltage is generated across it. This effect, called piezoelectricity, can be used to convert mechanical energy into an electrical form. Now, Zhong Lin Wang and co-workers1 at the Georgia Institute of Technology in the USA have built a device that generates an electrical current when an array of up to 1,000 nanowires is bent.

Credit: © 2007 AAAS

The nanowires were grown on either a gallium nitride or sapphire surface that serves as a bottom electrode. A saw-tooth-shaped silicon electrode coated with platinum forms an electrode above the bed of nanowires, and the entire device is sealed and embedded in water. An ultrasonic wave then drives the saw-tooth electrode up and down, so as to contact and bend the nanowires and produce a voltage that drives a current between the electrodes.

The nanogenerator delivers high power density compared with similar microgenerators, and improving the uniformity of the device should further increase the power output. Ultimately, these nanowire generators could simultaneously power large numbers of nanowire devices.