Light Triggers Multiple Motions In A Single Nanostructured Material

Molecular machines are capable of myriad motions, including rotation and even walking. It isn’t always easy, though, to translate those microscopic motions to the macroscopic scale. One team of chemists has now stepped up to that challenge by encoding multiple motions into a springlike material that responds to light (Nat. Chem. 2014, DOI: 10.1038/nchem.1859). The nanostructured “springs” are made from a liquid-crystalline polymer doped with an azobenzene molecular switch. Working with Oxford University’s Stephen P. Fletcher, Nathalie Katsonis and her coworkers from the University of Twente, in the Netherlands, took inspiration from plant tendrils that coil to access sunlight. The new material was designed to have a twist geometry, which produces ribbons that coil to different extents and with different handedness simply by cutting them from the film in different orientations. The differently cut spirals each have different responses to UV light, including winding, unwinding, or helix inversion. By connecting two spirals that move in different ways, the chemists built a pistonlike machine capable of moving a 2-mg magnet back and forth. The materials may be useful for driving microfluidic systems, Katsonis notes, because they don’t require electrical wiring to work.