Molecular Electric Motor Unveiled

The future of nanotech devices looks brighter now that single-molecule electric motors have been developed by chemists at Tufts University. Molecular motors powered by light and chemical reactions have been made before, but no electrically driven ones had been devised, despite theoretical predictions that such devices would be feasible. Charles Sykes and coworkers developed their single-molecule electric motor by using electrons from the asymmetric tip of a low-temperature scanning tunneling microscope (STM) to drive rotation of an asymmetric butyl methyl sulfide molecule adsorbed on a copper surface at 5 K (Nat. Nanotechnol., DOI: 10.1038/nnano.2011.142). Although the rotation is in both directions and thus has some randomness to it, there is a slight preference for one direction over the other, making it possible for the motor to perform useful work. Sykes’s group confirmed the preferential motion by using STM to monitor each rotational event in real time. Herre S. J. van der Zant of Delft University of Technology, in the Netherlands, comments that the work is “a fundamental study aimed at understanding how to drive and measure motion at a nanometer scale. Practical applications are still far away but may involve lab-on-a-chip products.”