Changing a surface from sticky to slippery could now be as easy as flipping a molecular light switch. Researchers at Rensselaer Polytechnic Institute have created an “optically switchable” material that alters its surface characteristics when exposed to ultraviolet (UV) light. The new material, which is described in the June 19 issue of the journal Angewandte Chemie International Edition, could have a wide variety of applications, from a protein filter for biological mixtures to a tiny valve on a “lab-on-a-chip.” The material was made by attaching spiropyran molecules to a widely used industrial polymer, poly(ether sulfone). Spiropyrans are a group of light-switchable organic molecules that exist in a colorless, “closed” form under visible light, but switch to a reddish-purple, “open” form when exposed to UV light. This change leads to an alteration of the new material’s polarity, or the chemical structure of its atoms. In switching from non-polar to polar, the material becomes less attractive to proteins that might stick to its surface. Exposing the material to UV light is like flipping a molecular switch, causing sticky proteins to detach from the surface and wash away in the liquid, the researchers report.