Sometimes, science does things just to see if it is possible. This seems to be one of those times. While I really wanted to have my long promised flying car by now, this is pretty cool too.
Controlled clockwise and anticlockwise rotational switching of a molecular motor
- U. G. E. Perera, F. Ample, H. Kersell, Y. Zhang, G. Vives, J. Echeverria, M. Grisolia, G. Rapenne, C. Joachim & S-W. Hla
- Nature Nanotechnology 8,46–51 (2013) doi:10.1038/nnano.2012.218
The design of artificial molecular machines1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 often takes inspiration from macroscopic machines13, 14, 15, 16, 17, 18, 19. However, the parallels between the two systems are often only superficial, because most molecular machines are governed by quantum processes.
Previously, rotary molecular motors3 powered by light4, 5, 6 and chemical7, 8, 9, 10, 11 energy have been developed. In electrically driven motors, tunnelling electrons from the tip of a scanning tunnelling microscope have been used to drive the rotation of a simple rotor12 in a single direction and to move a four-wheeled molecule across a surface13. Here, we show that a stand-alone molecular motor adsorbed on a gold surface can be made to rotate in a clockwise or anticlockwise direction by selective inelastic electron tunnelling through different subunits of the motor. Our motor is composed of a tripodal stator for vertical positioning, a five-arm rotor for controlled rotations, and a ruthenium atomic ball bearing connecting the static and rotational parts. The directional rotation arises from sawtooth-like rotational potentials, which are solely determined by the internal molecular structure and are independent of the surface adsorption site.