Nano gas turbine designed

One especially useful component of a microscopic machine would be a motor. Researchers from the Chung-Ang University in Korea have worked out how a nanoscale gas turbine made from nanotubes would work.

Nanotubes are rolled-up sheets of carbon atoms that can be narrower than a nanometer in diameter. A nanometer is one millionth of a millimeter, which is the span of 10 hydrogen atoms, or one-thousandth the diameter of an E. coli bacterium.

The researchers studied the friction between the outer nanotube surface and gas flowing past it with the idea that this friction could be used to provide engine torque, or the force required to turn a shaft.

They found that multiwall, or nested nanotubes, which experienced no friction between the tubes, can be used to make nanotube motors that can be efficiently operated and controlled by low liquid or gas flow rates.

The motor could eventually be used to drive nanoscale machines.

Previous research showed that an inner tube pulled partway out of a multi-wall carbon nanotube will snap back due to molecular electrostatic forces, and will continue to slide back and forth millions of times a second.

The researchers propose to use such a nanotube oscillator as a piston to pump the gas or liquid through a nanotube loop. The gas flow would spin a nanotube modified to have gear teeth. The gear-modified nanotube, embedded perpendicularly in the gas flow loop, would produce the motor's output in the form of a rotating shaft.

In the researchers' simulations, the speed of the oscillator determined the gas flow rate, which controlled the speed of the motor.

Nanotube motors could become practical within seven years, according to the researchers. The work appeared in the November issue of Nanotechnology.