Thursday, May 17, 2007

Nanogenerators:Batteries could be obsolete?

In the near future a well place nanogenerator into the shoes could be able to generate enough current to power a cellphone or small pc. The prototype "nanogenerator" was created by researchers at Georgia Tech's School of Materials Science and Engineering. Mechanical vibrations from walking, or sonic waves, or the flow of blood or other liquids can all generate current to power devices according to the researchers. Professor Zhong Lin Wang and his team developed the nanogenerators made of hundreds of tiny microscopic wires (nanowires) works like a miniature windmill with the vertically-aligned zinc oxide filaments waving back and forth when subjected to movement. Movement of the wires against silicon "zig-zag" electrodes, which contain thousands of nanometer-scale tips made conductive by a platinum coating produce tiny sparks of electricity. The nanogenerators take advantage of the unique coupled piezoelectric and semiconducting properties of zinc oxide nanostructures, which produce small electrical charges when they are flexed. The vertically-aligned nanowires are grown in the laboratory and are approximately a half-micron apart on gallium arsenide, sapphire or a flexible polymer substrate. A layer of zinc oxide is grown on top of substrate to collect the current. The electrode is then lowered on top of the nanowire array, leaving just enough space so that a significant number of the nanowires are free to flex 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. According to the inventors this is sufficient to power nanoscale devices without batteries or other external power sources. Still to be perfected the nanogenerator could be useful in medicine and implanted into the body to power electronic devices that measure blood pressure. The device was developed in part through a grant from the military's research agency and potential military use could include wearable biochemical sensors or trigger device to power explosives.
Defense Advanced Research Projects Agency (DARPA), funding for the project comes from the National Science Foundation and the Emory-Georgia Tech Center of Cancer Nanotechnology Excellence.

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