Nanogenerator produces electricity from ultrasonic waves
Atlanta (GA) – Scientists at the School of Materials Science and Engineering at the Georgia Institute of Technology have demonstrated a nano-scale generating that could provide electricity to microscopic machines by harvesting different types of energy from their environment.
According to Zhong Lin Wang, professor at Georgia Tech, the generator can convert mechanical energy from environmental sources such as ultrasonic waves, mechanical vibration or blood flow into continuous direct-current electricity. The device could enable nano-machines that are integrated into silicon or even into the human body without requiring batteries or external power sources.
Details about the nanogenerator, which is constructed fabricated using an array of zinc oxide nanowires, will be released in the April 6 issue of the journal Science.
“This is a major step toward a portable, adaptable and cost-effective technology for powering nanoscale devices,” said Zhong Lin Wang in a prepared statement. “There has been a lot of interest in making nanodevices, but we have tended not to think about how to power them. Our nanogenerator allows us to harvest or recycle energy from many sources to power these devices.”
On a more general level, the nanogenerator is built by growing an array of vertically-aligned nanowires approximately a half-micron apart on gallium arsenide, sapphire or a flexible polymer substrate. A layer of zinc oxide is grown on top of the substrate to collect the current. The researchers said that they also “fabricate silicon ‘zig-zag’ electrodes, which contain thousands of nanometer-scale tips made conductive by a platinum coating.”
The complete electrode is positioned on top of the nanowire array, leaving just enough space to allow a “significant” number of the nanowires to swing free within the gaps created by the tips. Moved by mechanical energy such as waves or vibration, the nanowires periodically contact the tips, transferring their electrical charges. By capturing the tiny amounts of current produced by hundreds of nanowires kept in motion, the generators produce a direct current output in the nano-Ampere range, the researchers explained.
Wang and his group believes that their nanogenerator could produce as much as 4 watts of power per cubic centimeter. That does not sound much, but the electricity generated would be enough to power bio-sensors, environmental monitors and even nanoscale robots, Wang said.