Adjusting the nano-switch

Scientists at the University of North Carolina at Chapel Hill and North Carolina State University have found that rotating a carbon nanotube can control its ability to conduct electrical current to another material. The finding is likened to controlling the flow of electricity to lights by turning a dimmer switch.

The discovery marks the first time scientists have been able to show the control of electrical resistance by rotating a nanostructure.

That knowledge is said to be especially useful to researchers working in wireless communications or micro-robotics because it would theoretically make it easier for them to design electronic devices and actuating systems at the nanoscale level.

The molecular size and mechanical and electronic properties of carbon nanotubes make them prime candidates for use as components in nanometer-sized electronic and actuating devices.

‘We found that we could change the electrical resistance between the carbon nanotube and a graphite substrate up to a factor of 50 by simply rotating the nanotube,’ said Dr Marco Buongiorno Nardelli, a research associate in physics at NC State. Being able to do this, he said, gives nanoscale-device designers a controllable, continuous means of converting mechanical signals into electrical signals.

‘Being able to adjust the electrical resistance in this way could, one day, lead to much faster, more energy – efficient electronic devices,’ said Dr Nardelli.

Dr Nardelli added that without its long-term practical applications, the team’s discovery is significant because it represents another building block in modern science’s understanding of nanotechnology fundamentals.

The transfer of electrons from one material to another has almost always been thought of in terms of energy conservation, with no attention being paid to momentum conservation, he said. ‘These experiments show us that momentum conservation plays a role, too.’