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Last Updated: Friday, 7 January, 2005, 12:41 GMT
Nano-propellers sent for a spin
Nano-rotor, Chemical Communications
The propeller motion is driven by hydrogen peroxide "fuel"
Metallic rods about 500 times smaller than the width of a human hair have been turned into tiny "propellers" by a Canadian research team.

The "nanorods" spin after becoming anchored to silicon wafers, Chemical Communications has reported.

Their motion is driven by addition of hydrogen peroxide (H2O2) to the solution in which they are contained.

A reaction at the free ends liberates gas bubbles to provide thrust, turning the rods at a near constant speed.

Only when the supply of hydrogen peroxide fuel is exhausted do the rods stop spinning.

Geoffrey Ozin and colleagues at the University of Toronto, Canada, used nanorods made up of a gold segment and a smaller nickel segment.

The rods attach to silicon wafers at the gold end. This metal does not react with hydrogen peroxide.

Nickel, on the other hand, acts as a catalyst in a "decomposition" reaction that produces oxygen and water from H2O2.

As oxygen bubbles off the nickel surface, it provides gas propulsion for the nanorods. The rods' behaviour was discovered entirely by accident.

Reversible spin

The tiny rods rotate in clockwise and anti-clockwise directions and exhibited more than one type of circular motion.

But researchers admit that if nano-machines are to have a future, ways must be found of getting different parts to interact as a functional whole.

Spinning nanorods, Chemical Communications
Oxygen bubbling off the nickel end causes the rods to spin
"Rotational motion is at the heart of many conventional machines, such as rotary engines, screws and clocks," said Professor Ozin.

"However, these machines clearly need more than just a rotor."

Nano-scale rotors have been built before. In 2000, Carlo Montemagno of University of California, Los Angeles (UCLA) used the biological molecule ATP synthase to drive a nickel rotor.

"Biological motors have done much cleverer things and some people have said 'that's cheating' because the clever thing was done by biology," said one researcher.

However, this scientist added, the rotors described by Professor Ozin's group did not seem to be controllable and were therefore not yet true nano-machines.

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