"This technology could eventually lead to wearable 'smart clothes' that can power hand-held electronics through ordinary body movements," said Professor Liwei Lin of the University of California in Berkeley, head of the international research team that developed the fibre nanogenerators.

"And because the nanofibres are so small, we could weave them right into clothes with no perceptible change in comfort for the user."

The flexible nanofibres are made from organic polyvinylidene fluoride, or PVDF, making them relatively easy and cheap to manufacture.

Previous efforts have focused on nanogenerators out of inorganic semiconducting materials, such as zinc oxide or barium titanate.

"Inorganic nanogenerators -- in contrast to the organic nanogenerators we created -- are more brittle and harder to grow in significant quantities," Professor Lin said.

Although the exact ratio of movement to power has yet to be determined, it appears that more vigourous movements result in more electricity generated.

"Surprisingly, the energy efficiency ratings of the nanofibres are much greater than the 0.5 to 4 per cent achieved in typical power generators made from experimental piezoelectric PVDF thin films, and the 6.8 per cent in nanogenerators made from zinc oxide fine wires," said the study's lead author, Chieh Chang.

"We think the efficiency likely could be raised further," said Professor Lin.

"For our preliminary results, we see a trend that the smaller the fibre we have, the better the energy efficiency."

"We don't know what the limit is."