Humans have long been trying to make the dream of nanoscopic robots come true. It's getting closer each time nanoscience produces components for molecular-scale machines.
One such device is a rotor; a movable component that rotates around an axis. Trying to observe such rotational motion on the molecular scale is an extremely difficult undertaking but Japanese researchers at the Universities of Osaka and Kyoto have met this challenge. As Akira Harada and his team report in the journal Angewandte Chemie, they were able to get "snapshots" of individual molecular rotors caught in motion.
As the subject of their study the researchers chose a rotaxane. This is a two-part molecular system: A rod-shaped molecule is threaded by a second, ring-shaped molecule like a cuff while a stopper at the end of the rod prevents the ring from coming off. The researchers attached one end of the rod to a glass support. To observe the rotational motions of the cuff around the sleeve, the scientists attached a fluorescing side chain to the cuff as a probe.