Imagine if all you had to do to charge your iPod or your BlackBerry was to
wave your hand, or stretch your arm, or take a walk? You could say goodbye to
batteries and never have to plug those devices into a power source again.
In research presented here today at the American
Chemical Society's 237th National Meeting, scientists from Georgia describe
technology that converts mechanical energy from body movements or even the flow
of blood in the body into electric energy that can be used to power a broad
range of electronic devices without using batteries.
"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.
Last year Wang's group presented a study on nanogenerators driven by ultrasound.
Today's research represents a much broader application of nanogenerators as
driven by low-frequency body movement.