New Nanogenerator may charge iPods and cell phones

"This research will have a major impact on defense technology,
environmental monitoring, biomedical sciences and even personal
electronics," says lead researcher Zhong Lin Wang, Regents' Professor,
School of Material Science and Engineering at the Georgia Institute of
Technology. The new "nanogenerator" could have countless applications,
among them a way to run electronic devices used by the military when
troops are far in the field.

The researchers describe harvesting energy from the environment by
converting low-frequency vibrations, like simple body movements, the
beating of the heart or movement of the wind, into electricity, using
zinc oxide (ZnO) nanowires that conduct the electricity. The ZnO
nanowires are piezoelectric — they generate an electric current when
subjected to mechanical stress. The diameter and length of the wire
are 1/5,000th and 1/25th the diameter of a human hair.

In generating energy from movement, Wang says his team concluded that
it was most effective to develop a method that worked at low
frequencies and was based on flexible materials. The ZnO nanowires met
these requirements. At the same time, he says a real advantage of this
technology is that the nanowires can be grown easily on a wide variety
of surfaces, and the nanogenerators will operate in the air or in
liquids once properly packaged. Among the surfaces on which the
nanowires can be grown are metals, ceramics, polymers, clothing and
even tents.

"Quite simply, this technology can be used to generate energy under
any circumstances as long as there is movement," according to Wang.

To date, he says that there have been limited methods created to
produce nanopower despite the growing need by the military and defense
agencies for nanoscale sensing devices used to detect bioterror
agents. The nanogenerator would be particularly critical to troops in
the field, where they are far from energy sources and need to use
sensors or communication devices. In addition, having a sensor which
doesn't need batteries could be extremely useful to the military and
police sampling air for potential bioterrorism attacks in the United
States, Wang says.

While biosensors have been miniaturized and can be implanted under the
skin, he points out that these devices still require batteries, and
the new nanogenerator would offer much more flexibility.

A major advantage of this new technology is that many nanogenerators
can produce electricity continuously and simultaneously. On the other
hand, the greatest challenge in developing these nanogenerators is to
improve the output voltage and power, he says.