Stanford University mechanical engineering graduate student Elliot Hawkes wanted to find out how geckos (small tropical lizards) climb walls. Many geckos have specialized toe pads that allow them to climb smooth vertical surfaces. Now Hawkes is climbing sheer glass buildings on campus, testing a controllable adhesive system that sticks to glass and supports a person’s weight.
Each handheld pad is covered with 24 adhesive tiles, each covered with sawtooth-shaped silicone rubber structures about the width of a human hair. Pads are connected to springs that become less stiff the further they are stretched; the user pulls on the springs, applying an identical force to each adhesive tile, and flattens the rubbery structures to the glass. Stickiness happens, and when the user releases the load tension so that only the tips touch glass, the gecko pad lets go.
Prospective applications have scientists asking new questions. Can manufacturing robots with gecko hands lift large glass panels or liquid-crystal displays? Could the National Aeronautics and Space Administration (NASA) Jet Propulsion Lab apply gecko technology to a spacecraft’s robotic arms? “The ability of the device to scale up controllable adhesion to support large loads makes it attractive for several applications,” says Mark Cutkosky, the Fletcher Jones Chair at Stanford’s School of Engineering and senior author of the research, published in the Journal of the Royal Society Interface in November 2014.