Any future artificial transporters and robots operating at the nanoscale are likely to require molecules capable of directional translational movement over a surface. Even the design of such molecules is a daunting task, however, as they need to be able to use light, chemical or electrical energy to modulate their interaction with the surface in a way that generates directional motion. Our collaborators from Groningen now unveil just such a molecule, made by attaching four rotary motor units to a central axis. Inelastic electron tunneling, performed in Empas Molecular Surface Science Group, induces conformational changes in the rotors and propels the molecule across a copper surface. By changing the direction of the rotary motion of individual motor units, the self-propelling molecular 'four-wheeler' structure can follow random or preferentially linear trajectories. This design provides a starting point for the exploration of more sophisticated molecular mechanical systems, perhaps with complete control over their direction of motion.
Kudernac et. al Nature 479 (2011) 208
Echoes in the media