 The Motor in Mid-Spin
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July 24, 2003 — Scientists in the United States say they have made a motor that is more than 250 times smaller than the human hair, a breakthrough in the new frontier of nanotechnology.
The gadget comprises a gold blade attached to an axle made from a carbon nanotube whose ends are anchored to two silicon dioxide electrodes.
Voltage flows through the electrodes and down the conductive nanotube to rotate the blade. Three other electrodes — two placed either side of the axle, one underneath — provide additional voltage control, so that the speed of the blade, its direction and position can be governed precisely.
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The arrangement, so tiny that it has been imbedded in a silicon chip, is not the smallest nanoscale device in the world; that title belongs to experimental "bio-switches" made from molecular DNA and driven by chemicals.
But, said the inventors, it offers several advantages. As an electrical-mechanical device, it can tolerate wider temperature ranges, operate in a vacuum and cope with harsher chemical environments than its "bio" equivalents.
Nanotechnology is an eagerly researched area because of the potential it offers for the next generation of miniaturized devices in communications, consumer products and medicine.
Scientists working with electromechnical systems have met with frustrations, for conventional metals and plastics can throw up unexpected performance problems when they are sized down to microscopic size.
That explains a surge of interest in carbon nanotubes, a new material comprising long, resilient chains of carbon atoms that conduct heat and electricity.
The research, led by Alex Zettl of Lawrence Berkeley National Laboratory in Berkeley, California, is published in Thursday's issue of the journal Nature.
The invention is important because it proves that electromechanical devices can be made on such a small scale using simple, elegant sources to drive them. Up until now, nanoscale motors have needed help from large and cumbersome external sources, such as lasers and magnets, in order to operate.
The invention has several potential outlets, said Zettl.
The blade could act as a switch in next-generation communications, working as a rotating mirror for laser signals. It could also act as a tiny propeller to drive fluids.
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