Liquid Locomotion

Thanks to a specially textured surface developed in the lab of Evelyn N. Wang ‘00, an assistant professor of mechanical engineering, researchers can now ensure that droplets of liquid spread across a surface in only one specific direction. Wang and her students made the material at the MIT Microsystems Technology Laboratories by etching a silicon wafer to produce a grid of tiny pillars. Then they coated the pillars with gold on one side to make them bend in one direction, causing liquid that is dropped onto the chip to spread only in that direction. “Nobody had really studied this kind of geometry, because it’s hard to fabricate,” Wang says. She says such systems could be used for a wide variety of applications, such as ink-jet printing or manipulating biological molecules on the surface of a chip for medical testing.