Ben Feringa and colleagues used a molecule with a central carbon-carbon double bond that functioned as an axle. The upper part of the molecule acted as a rotor while the lower part was the stator. The team added the molecules to a liquid crystal film and illuminated them with light with a wavelength of 365 nm.
The light caused a photochemical isomerization around the double bond and changed the helicity of the molecule from right- to left-handed. A thermal step then caused the molecule to revert to its right-handed state. Two sets of a photochemical step followed by a thermal step resulted in the molecule rotating through 360°.