Twisted nanotubes have spring

Researchers from the University of North Carolina at Chapel Hill have found a way to use carbon nanotubes -- rolled-up sheets of carbon atoms that form naturally in soot -- as tiny springs for microscopic devices.

The researchers combined an atomic force microscope with scanning electron microscopy to position tiny paddles on top of a nanotube. They used the paddles as handles to force the nanotube to twist, which stored energy in the same manner as the twisted rubber band that turns a toy airplane's propeller.

The scanning electron component allowed the researchers to see the paddles as they touched them with the atomic force probe, which is sensitive enough to measure the small forces needed to twist the nanotube.

The process of twisting the tubes stiffened them by as much as 20 times, an effect the researchers are currently working to explain. The tiny springs could be used as chemical sensors and frequency sources for communications or computational electronics.

It will be more than five years before the devices can be used practically, according to the researchers. The work appeared in the November, 2002 issue of the Journal Vacuum Science and Technology B.