Nanogenerators May Spark Miniature Machines

Researchers have developed a new technique for powering nanometer-scale devices without the need for bulky energy sources such as batteries. By converting mechanical energy from body movement, muscle stretching or water flow into electricity, these "nanogenerators" could make possible a new class of self-powered implantable medical devices, sensors and portable electronics.

Described in the April 14th issue of the journal Science, the nanogenerators produce current by bending and then releasing zinc oxide nanowires – which are both piezoelectric and semiconducting. The research was sponsored by the National Science Foundation (NSF), the NASA Vehicle Systems Program and the Defense Advanced Research Projects Agency (DARPA).

"Our bodies are good at converting chemical energy from glucose into the mechanical energy of our muscles," Wang noted. "These nanogenerators can take that mechanical energy and convert it to electrical energy for powering devices inside the body. This could open up tremendous possibilities for self-powered implantable medical devices."
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A scanning electron microscope image (top) shows an array of zinc oxide nanowires. Middle image shows a schematic of how an AFM tip was used to bend nanowires to produce current. Bottom image depicts output voltages produced by the array as it is scanned by the AFM tip. Credit: Z. L. Wang