Researchers in the US and Finland claim they have found a way of improving the performance of motor commutators by using microscopic tubes of pure carbon, just 30nm in diameter.  They found that brush contact pads made of these “nanotubes” have ten times less resistance than conventional carbon-copper composite brushes.

The researchers – from Rice University in Texas, and the University of Oulu in Finland – replaced the composite brushes in a motor with millimetre-square blocks containing millions of the nanotubes (as shown above). They discovered that the blocks (shown highly magnified below) maintained better contact with the motor’s spinning disc than standard brushes.

The nanotubes, each about 3,000 times thinner than a human hair, are lightweight, durable and good conductors of heat and electricity. When packed together to form miniature “forests”, they also regain their shape very quickly after being compressed.

“This elasticity is something that`s not found in existing composites that are used for brush contacts, and that`s the essence of why the nanotube brush contacts perform better,” explains Robert Vajtai, a faculty fellow at Rice University. “They keep much more of their surface area in contact with the spinning disc.”

The researchers believe that the improved contact between the surface of the spinning disc and the brush accounts for the 90% reduction in lost energy.

“The findings show that nanotubes have a great deal of practical relevance as brush contacts,” says Professor Pulickel Ajayan, the lead researcher at Rice. “This could be a very interesting, near-term application for nanotubes”.