From slippery to sticky with the flip of a switch

Filed in archive Materials on June 21, 2006

Changing a surface from sticky to slippery could now be as easy as flipping a molecular light switch. Researchers at Rensselaer Polytechnic Institute (RPI) have created an "optically switchable" material that alters its surface characteristics when exposed to ultraviolet (UV) light. The new material could have a wide variety of applications, from a protein filter for biological mixtures to a tiny valve on a "lab-on-a-chip", says an RPI press release.

To make the new materials, researchers attached 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. Exposing the material to UV light is like flipping a molecular switch, causing sticky proteins to detach from the surface and wash away.

"We asked ourselves, can one use light to help the proteins hop on and hop off? We have shown that when one changes light, the proteins don't stick as well," said Georges Belfort, the Russell Sage Professor of Chemical Engineering at Rensselaer.

Belfort envisions a number of potential applications for the materials, ranging from new membranes for treating polluted water to the targeted release of drugs in the body.

For example, in recent years researchers have developed "lab-on-a-chip" technology for automating laboratory processes on extremely small scales. Belfort notes that the new material could be employed as a surface valve that can be opened and closed by applying light, offering the ability to control liquid flow in a chip's ultra-tiny channels.