UK technology group QinetiQ (formerly Dera) has switched its research into power-scavenging circuits from electric shoes to devices that fit on to mechanical systems and use their motion to produce power for small devices.
The company has suspended work on putting piezoelectric de-vices into shoes. The Electric Shoe Company, a subsidiary of industrial shoemaker Texon International, was set up last year to carry on the footwear work.
Adrian Bowles, technical leader for Qinetiq's piezoelectric research, said: "We took it on in a consulting role from Texon. We are looking at other applications for self-contained power sources, but not in the application of a shoe."
He says the focus is on mechanical systems and QinetiQ is building small demonstrators.
One problem raised by researchers at the Massachusetts Institute of Technology (MIT) was that of converting the power released by the flexing of a piezoelectric material, leading them to go to a switched power converter from simple passive electronics because of the low frequencies involved in walking.
"I have seen MIT's circuits, but what concerned me was that there was a huge bulk of components to make the circuit," said Bowles. "We looked at simple analogue circuits to step up the current and step down the voltage."
He says the faster motion of some mechanical systems will solve power conversion problems: "We are trying to stimulate the piezo material at higher frequencies. That way, you get a higher charge naturally."