Geckos attach and detach their adhesive toes in milliseconds while running with reckless abandon on nearly any surface. The adhesive on gecko toes differs dramatically from that of conventional adhesives. Conventional pressure-sensitive adhesives (PSAs) are soft viscoelastic polymers that degrade, foul, self-adhere, and attach accidentally to inappropriate surfaces. In contrast, gecko toes bear angled arrays of branched, hair-like fibers (setae) formed from stiff, hydrophobic keratin that act as a bed of angled springs with an effective stiffness similar to that of PSAs. Setae are selfcleaning and maintain function for months during repeated use in dirty conditions. Setae are an anisotropic “frictional adhesive” in that adhesion requires maintenance of a proximally directed shear load. Thus, gecko setae resist inappropriate bonding and are capable of easy and rapid attachment and detachment. Engineered adhesive nanostructures inspired by geckos may become the glue of the future—and perhaps the screw of the future as well.
Kellar Autumn is an associate professor of biology at Lewis & Clark College in Portland, Oregon. Autumn received his BA degree in mathematics and biology at the University of California, Santa Cruz, in 1988, and his PhD degree in integrative biology at the University of California, Berkeley, in 1995. He continued at UC–Berkeley as an Office of Naval Research postdoctoral fellow until 1998, and joined the faculty of biology at Lewis & Clark College in the same year.
Autumn's research focuses on the biomechanics, physiology, and evolution of animal locomotion. He is best known for his discovery of the mechanism of adhesion in geckos, which inspired a new subfield of research on adhesive nanostructures. Autumn and his colleagues hold a patent for synthetic adhesives inspired by gecko feet.
Autumn can be reached at the Department of Biology, Lewis & Clark College, 0615 SW Palatine Hill Rd., Portland, OR 97219, USA; tel. 503-768-7502, fax 503-768-7658, e-mail email@example.com, and URL www.lclark.edu/˜autumn.