UCLA chemists have created the first nano valve that can be opened and closed at will to trap and release molecules. It can be used as a drug delivery system.

It consists of moving parts — switchable rotaxane molecules that resemble linear motors attached to a tiny piece of glass (porous silica), which measures about 500 nanometers. Tiny pores in the glass are only a few nanometers in size.

University of California – Los Angeles news release