A nanogenerator is a device that generates energy on a nanoscale level, using tools such as nanowires. The most well-known example is Zhong Lin Wang’s nanogenerator, which converts ultrasonic waves into electricity using piezoelectricity. Other approaches include chemical energy, heat, and electromagnetic waves. Nanoscale power generation has the potential to greatly improve power generation and storage density, leading to advancements such as electric cars with longer battery life.
A nanogenerator is any nanoscale device used to generate energy. Usually this would mean smaller than a micron (1000 nanometers or 1/1000 of a millimeter) in size, but in practice the word has been used to describe generators as large as 2 mm or 2,000,000 nanometers in diameter. Alternatively, a nanogenerator can be any generator that uses nanoscale tools, such as nanowires, to generate electricity.
So far, the term “nanogenerator” has mostly been used in reference to the work of Zhong Lin Wang and colleagues at the Georgia Institute of Technology. Wang’s team built a nanogenerator that uses an array of zinc oxide nanowires to convert ultrasonic waves into electricity. The nanogenerator exploits the piezoelectric effect, a phenomenon manifested by some materials whereby mechanical stress is converted directly into electric current. Wang visualizes the nanogenerator integrated into future nanomachines or implants that can obtain energy directly from the vibrations inside the human body caused by the circulatory system. Dr. Wang’s prototype nanogenerator was 2 mm in size, but he hopes to reduce it to nanoscale dimensions and make it ready for adoption by 2011.
When nanoscale machines were first conceived by Eric Drexler in the late 1970s, one of the main objections that arose regarding their feasibility was “How should they be powered?” Dr. Wang’s work answered this question when it was presented in 2007. However, the approach of using piezoelectricity to power nanodevices is still just one among many: other possible approaches to generating or distributing energy on nanoscale include chemical energy, using nanowires for energy from a macroscale source, obtaining energy directly from heat, or an electromagnetic wave-based generator such as UV light.
Although overshadowed by Dr. Wang’s team, there has been some other work on nanogenerators. Dozens if not hundreds of academic and industry groups are researching nanoscale power generation. Nanoscale power generation can offer order-of-magnitude improvements in power generation and storage density over current technologies. This could enable electric cars that can run for hundreds or even thousands of miles without recharging, if technology advances far enough.
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