Smart shoes are one step closer to reality today, thanks to the development of miniature mechanical power plants by the Georgia Institute of Technology.

Researchers there have created a new type of small-scale generator that produces alternating current through the stretching and releasing of zinc oxide wires.

The nanoscale 'flexible charge pump' uses the piezoelectric wires to harvest mechanical energy from the environment, raising the possibility of smart clothing that generates power when you walk, self-powered gadgets and even tiny sensors that live in your bloodstream.

Hair today, power tomorrow

The miniature wires are just three microns thick - 25 times thinner than a human hair - and generate a small voltage (45 millivolts) when stretched and released.

Professor Zhong Lin Wang at the Institute envisages arrays of the minuscule electricity generators woven into materials to provide high levels of power.

Ultimately, he says, "Self-powered nanotechnology could be the basis for a new industry. That's really the only way to build independent systems."