Light-Driven Molecule Moves Microscale Objects

Chemists at Rijksuniversiteit Groningen and Technische Universiteit Eindhoven, both in the Netherlands, have designed and synthesized a helical molecule that rotates when exposed to ultraviolet radiation and heat, carrying along with it objects tens of thousands of times larger. The molecule, which they described in the March 9 issue of Nature, illustrates the potential of such structures to operate as rotary motors in nanomachines.

In their work, they doped liquid crystal with the molecule at 1 percent by weight and placed a 28-µm-long glass rod atop a film of the doped material. Exposing the film with 365-nm radiation caused the rod to rotate in the same direction as the molecular motor at an average rate of 0.67 rpm.

Observations using atomic force microscopy and optical profilometry indicate that the rotation of the molecule changes the texture of the liquid crystal, imparting torque to objects on the film that induces their rotation.