Wee Walker

If each bit of digital data could be represented by a single molecule, memory devices could shrink by more than three orders of magnitude. But manufacturing such devices requires a simple way to keep molecules straight and organized. A team led by University of California, Riverside, chemist Ludwig Bartels has come up with a possible solution: molecules that walk in a straight line, without guides or templates.

Called 9,10-dithioanthracene, or DTA, the new molecule sports two sulfur atoms protruding from a central structure made of linked benzene molecules. The Riverside researchers deposited DTA molecules on a smooth copper surface and cooled them to about -223 degreesC; they found that the molecules would then form rows and begin to move in straight lines – almost as if they were walking.

“Effectively, [the molecule] kind of rotates around each of the feet and wobbles forward or wobbles backward,” says Bartels. Biomolecules such as DNA and proteins have exhibited similar behaviors, but they’ve generally required some kind of molecular guide to align them. By contrast, all Bartels’s molecule needs is a bit of heat.

The wobbly molecules won’t show up in the next Dell computer, but Bartels believes that similar molecules could ultimately be useful in making molecular memory devices. “The work is amazing,” says Rice University chemist James Tour, a leader in the field of molecular transport devices. The major challenge, he cautions, will be to tailor molecules to move in the same way on surfaces other than copper.