Researchers build molecular motor with electrically controlled rotation
Simulations showed that the molecule’s ability to conduct electricity could rise by as much as 100 times as it rotated.
An international research team has demonstrated a motor consisting of a single molecule connected to gold electrodes. Electricity drives its rotation, and reversing the voltage polarity changes the direction of movement, the researchers reported.
The design draws on the Archimedes screw, a rotating spiral traditionally used to raise water. Michael Pittelkow’s group at the University of Copenhagen created the spiral molecule, which measures a few millionths of a millimeter and bonds to gold through sulfur atoms. At Israel’s Weizmann Institute of Science, Oren Tal and Anil Kumar Singh led researchers who placed individual molecules between atomically sharpened gold tips. Changing the gap allowed them to compress or stretch each molecule.
The team found that electrons impart angular momentum as they pass through the spiral, setting it in motion. Rotation becomes continuous above a threshold voltage. The experiments also showed that the moving molecule carried electricity more efficiently than the stationary molecule.
To explain that behavior, Fabian Pauly, Léon Martin and Yuta Ito at the University of Augsburg performed quantum mechanical simulations using the LiCCA supercomputer. Their calculations indicated that rotation lets the molecule reach arrangements that favor electrical conduction but that it normally avoids at rest. With collaborators in Copenhagen and Wuhan, the researchers also built a simplified model reproducing the measured rotation and current increase. They said the findings could eventually support molecular electronics, spintronics and systems for manipulating tiny amounts of fluid.
