U.S. researchers working on nanogenerators have moved one step closer to creating power sources for gadgets like cellphones and iPods by deriving electric energy from body motion, including the beating of a person's heart and the coursing of blood through veins.

The researchers from the Georgia Institute of Technology described how miniature generators using zinc oxide nanowires could also harvest energy from the environment, turning low-frequency vibrations like the movement of a light breeze into electricity.

"Quite simply, this technology can be used to generate energy under any circumstances as long as there is movement," lead researcher Zhong Lin Wang, said in a news release. He presented his research at the American Chemical Society's National Meeting Thursday.

The key is tiny zinc oxide nanowires, measuring 1/5,000th the diameter of a human hair. The nanowires are piezoelectric, which means they generate an electric current when subjected to mechanical stress, thus the ability to harness the energy in a body movement or a faint breeze.

Another major advantage, according to Wang, is that the nanowires can be grown on a variety of surfaces — metals, ceramics, polymers, clothing and even tents — and they can operate as nanogenerators in both air and liquid.

Could power medical monitors

To create a generator, a forest of nanowires would be grown to a height of one micron on gallium arsenide, sapphire or a flexible polymer substrate. Then a wavy plate of silicon electrodes would be pressed on top to generate an electric charge, according to a description provided by Wang to Scientific American magazine.

The biggest challenge now is to improve output voltage and power, said Wang, Regents' Professor at the institute's School of Material Science and Engineering.

Practical applications could come within five years in the medical field, where nanogenerators could provide the small amount of electricity needed for biomedical sensors such as those that monitor blood sugar levels, blood pressure and heart rates, according to an article in the Washington Times.

More mainstream applications for energy hogs like mobile phones, iPods and other wireless gadgets could come within the decade, with generators being woven into clothing and the soles of shoes to harvest the mechanical energy of walking or the rustling of fabric, Wang told Scientific American.

The research was funded by several American agencies including the Defense Advanced Research Projects Agency, the Department of Energy, the National Institutes of Health and the National Science Foundation.