The molecule-sized gearshaft, shown here in a computer simulation, consists of a cylinder of carbon atoms known as a "nanotube", with individual atoms of the organic molecule benzyne attached to the side to form gear teeth. It is one of the first suggested practical uses for nanotubes, whose structure was first suggested by Sir Harold Kroto, the British scientist who won the 1996 Nobel Prize for Chemistry.
The Nasa scientists at the Ames research centre in Mountain View, California, have not yet built the nanogear system. But they are increasingly confident that they could be constructed and form part of miniature self-repairing machines.
The idea is part of the growing field of nanotechnology, which uses structures at the molecular scale to build tiny, efficient machines.
"One practical use of nanotechnology would be to build a 'matter compiler'," said Creon Levit, one of the Nasa team. "We would give this machine, made of nano-parts, some raw materials, like natural gas for example.
"A computer program would specify an arrangement of atoms and the matter compiler would arrange the atoms from the raw material to make a macro- scale machine or parts."
Nanotechnology is expected to become a worldwide industry worth billions of pounds once scientists break through the problems of precise manufacture.
Though it may take decades, they expect to be able eventually to produce self-repairing machines that could, for example, be injected into the blood to seek out and clean away harmful fat deposits.
Al Globus, one of the team working at the Ames centre, said "A step along the way to making an aerospace 'matter compiler' is an even smaller hypothetical machine - the assembler/replicator.
"It can make a copy of itself from raw materials, just as a living cell can duplicate itself.
"Then we would write computer programs to make aerospace materials, parts and machines at atomic levels of detail. They would have tremendous strength and thermal properties."Reuse content