'Electron turbine' could print designer molecules

By # NewScientist.com news service
# Kate McAlpine

A carbon nanotube that spins in a current of electrons, like a wind turbine in a breeze, could become the world's smallest printer or shrink computer memory, UK researchers say.

The design is simple. A carbon nanotube 10 nanometres long and 1 nm wide is suspended between two others, its ends nested inside them to form a rotating joint. When a direct current is passed along the tubes, the central one spins around.

That design has as yet only been tested using advanced computer simulations by Colin Lambert and colleagues at Lancaster University, Lancashire, UK.

But Adrian Bachtold of the Catalan Institute for Nanotechnology, who was not involved in the work, intends to build the electron turbines and says it should be straightforward.

Researchers have made or designed a range of small-scale motors in recent years, using everything from DNA to light sensitive molecules to cell-transport proteins.

The Lancaster design is one of the simplest yet. Imagined applications for nanomotors range from shrinking optical communications components to new forms of computer memory.
Tiny turbine

Conventional water or wind turbines spin by deflecting oncoming air or water in one direction. This causes a reaction force to push them in the opposite direction.

Similarly, when electrons move through the nanotube turbine, they tend to bounce off its spiral arrangement of carbon rings in a particular direction. This redirects the electrons into a spiral flow, and causes the tube to rotate in the opposite direction.

The Lancaster team is confident this electron "wind" can overcome any friction forces that would prevent the middle tube spinning. They also hope to minimise friction at the joints by making the nanotubes as smooth as possible.
Tiny inkjet

The Lancaster researchers say their motor could be used to pump atoms and molecules through the spinning middle tube. Multiple pumps could precisely control a chemical reaction, driving atoms in a pattern to engineer new molecules. "It's like a nanoscale inkjet printer," says Lambert.

Atoms pumped through the motor could also be used to represent digital data, with an array of motors shuttling atoms between the 1 and 0 ends of the middle tube to store or process information. This method could store data in a space about 10 times smaller than today's state-of-the-art commercial systems, says Lambert.

"The work of Lambert's group is exciting," says Bachtold, "the proposed motors should be rather straightforward to fabricate". But he points out that only experiments will reveal whether this new nanomotor design lives up to its promise.

A paper on the electron windmills will be published in Physical Review Letters this month. A pre-review version is available on the arXiv pre-print website.