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Critter Chemistry

June 12, 2000

Gecko Bonding

Sophie Rovner

What's behind the remarkable ability of geckos to dash up smooth vertical surfaces and even stick to a ceiling? Robert J. Full, professor of biology at the University of California, Berkeley; Kellar Autumn, assistant professor of biology at Lewis & Clark College, Portland, Ore.; and their colleagues noted that these lizards uncurl their toes like an inflating party favor when putting their feet down and peel the toes back up as if removing a piece of tape when they step away. This precise footwork may result from the fact that the adhesive force depends on how the hairs on the gecko's feet attach and detach from a surface [Nature,405, 681 (2000)]. The foot of a Tokay gecko is covered with 500,000 fine hairs, each tipped with hundreds of projections known as spatulae. Working with single hairs, the researchers found that the strongest attachment results from jamming a hair--and hence the pads on the end of the spatulae--into the surface and then pulling it slightly downward before attempting to detach it. If all the hairs on one foot were attached this way, the adhesive force would total about 100 newtons. The million hairs contained in a dime-sized spot could lift a child weighing 45 lb. The researchers believe that the adhesion is based on van der Waals interactions. The gecko's bonding capabilities may provide the inspiration for a clean new adhesive.

Chemical & Engineering News
ISSN 0009-2347
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