For the past several years, scientists from around the world have been engaged in the development of nanogenerators – tiny piezoelectric devices capable of generating electricity by harnessing minute naturally-occurring movements, such as the shifting of clothing or even the beating of a person's heart. So far, while they may have worked in principle, few if any of the devices have been able to generate enough of a current to make them practical for use in consumer products. Now scientists from the Georgia Institute of Technology are claiming to have created "the world's first practical nanogenerator."
The device was developed by a team led by Dr. Zhong Lin Wang. Its charge comes from zinc oxide nanowires, which generate an electrical current when flexed or strained. Because the nanowires are so tiny (500 of them can fit inside the width of a human hair), Wang's team was able to deposit millions of them onto flexible polymer chips, each chip about a quarter the size of a postage stamp. When five of the chips – each one a separate nanogenerator – were stacked together, their combined output current was about 1 microampere at 3 volts. That's over 150 times the voltage that the team first achieved six years ago, and is about equivalent to that generated by two regular AA batteries.
To charge the nanogenerator, the scientists simply squeeze it between their fingers. In a demonstration at last month's 241st National Meeting & Exposition of the American Chemical Society, they used it to light an LED bulb, and to power a liquid crystal display. Wang believes that by introducing more nanowires per generator, and stacking more generators together, enough power could be produced to run an iPod or charge a mobile phone.
"This development represents a milestone toward producing portable electronics that can be powered by body movements without the use of batteries or electrical outlets," he said. "Our nanogenerators are poised to change lives in the future. Their potential is only limited by one's imagination."
Georgia Tech is now looking for a company interested in producing the nanogenerator commercially, with Wang estimating that it could hit the market within three to five years. Its first use could be in environmental sensors, which would store power in a capacitor, then use it to wirelessly transmit data.
