Electrons will jump from the metal tip of an electrical source to a lever coated in nanoparticles made of gold, the researchers discovered. The jumping electrons pull the lever toward the tip, closing a simple circuit that may be the smallest ever devised.

A circuit this small is "fantastically sensitive," chemistry professor and lead researcher Al-Amin Dhirani explained. "Such a circuit could make possible a biosensor that is activated by the reaction of just one molecule" -- for instance, a single molecule of DNA left at the scene of an otherwise perfect crime.

Archimedes of Atomic Architecture

The golden nanocircuit's architecture might impress even Archimedes, the mechanical genius whose super-size catapults, levers, screws and hoists helped protect ancient Greece from marauding invaders.

"The device we built has an extremely flexible cantilever coated with a gold film," Dhirani told NewsFactor. "A sharp tip was brought close to the gold nanoparticles tethered to the film, and the distance between the tip and the nanoparticles was on the order of [a] nanometer," or one-billionth of a meter.

The gold film and the sharp tip are nanoscale electrodes that control electron movement -- one electron at a time.

"A voltage between the tip and the film tends to drive electrons between these two electrodes via the nanoparticles," Dhirani said. "When an electron is on the nanoparticle, it creates an electric field, pulling the cantilever towards the tip," and closing the circuit.

Neat Achievement

Reactions to the research by other experts have been mixed, ranging from enthusiasm laced with cautionary reservations to sharp criticism.

"Dhirani and his team have developed a combined electrical-mechanical technique which is rather novel and a neat achievement," said Andy Sachrajda, a nanoelectronics expert and group leader of the Quantum Physics Institute for Microstructural Sciences at Canada's National Research Council.

"While it is too early to speculate on any individual applications, it is encouraging that this sort of mechanical device can detect forces at the single electron level at room temperature," Sachrajda added.

High-Powered Hybrid

Single electrons and far-away planets share similar detection techniques. Planets beyond our solar system are too distant to detect directly and individual electrons too small, so scientists use so-called "indirect detection techniques" that examine the effects these invisible objects have on their visible surroundings.

Planets exert minute but detectable gravitational effects on nearby stars, for example, and single electrons alter electric currents. The gold nanocircuit detects a single electron through its effect on the flexible microscopic lever. (continued...)

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