Molecule makes ring rotor

At the size-scale where we live, it takes a considerable amount of force to get something moving, and keep it moving. At the molecular scale, however, everything above absolute zero is constantly moving.

The trick to making nanoscale machines is finding ways to control this molecular motion.

Researchers from the University of Edinburgh in Scotland have interlocked large, ring-shaped molecules to make a molecular rotor that moves in only one direction. The molecule could eventually be used as a nanoscale motor or winch.

The molecular rotor contains one large ring with two or three small rings that move around it. Two small rings complete a cycle around four binding sites on the larger ring during a sequence of six light-driven chemical reactions. Different wavelengths cause reactions that break the hydrogen bonds holding one of the two small rings to a site on a larger ring.

The rings are moved one at a time and each time a ring makes a move, it is forced to move in the direction not blocked by the second ring.

Although the molecular movement during each step happens in a millionth of a second, the chemical reactions take 5 to 20 minutes each, meaning that the prototype takes an hour to complete a rotation.

The molecular rotor could be used in practical applications in 10 to 20 years, according to the researchers. The work appeared in the July 10, 2003 issue of Nature.