American Scientist

March-April 2006

Volume: 94 Number: 2

Seen from the underside, a tokay gecko displays its unique feet to good advantage. Geckos generate remarkably strong adhesive forces with the pads on their toes, allowing them to run on smooth vertical or even inverted surfaces. The structures that generate these forces—ridges covered with hairs that split into hundreds of tiny endings—have been known for some time, but how they worked has remained controversial until recently. In "How Gecko Toes Stick," Kellar Autumn summarizes current knowledge about gecko adhesion and recounts his own experiments, which confirmed the tiny van der Waals force as the source of the gecko's ability to stick to nearly anything. The exertion of such extreme adhesive force may allow a falling gecko to defy gravity by slapping a foot across a passing leaf, but a gecko on a ginkgo tree is still a rare sight. (Photograph by Martin Harvey/NHPA/Photo Researchers, Inc.)