Copyright 2000 Telegraph Group Limited  
June 08, 2000, Thursday


LENGTH: 294 words

HEADLINE: News: Gripping solution to mystery of geckos

BYLINE: By Roger Highfield Science Editor

THE mystery of how geckos scurry across ceilings has been solved by scientists who believe it should be possible to exploit the "intermolecular glue" in a new generation of dry adhesives.
The clinging properties of the feet of these lizards are well known, and their anatomy has been described for more than a century. Yet they have eluded attempts to understand how they achieve these gripping feats. Today, in the journal Nature, Prof Robert Full of the University of California, Berkeley, shows that the secret lies in their hairy feet.
Each foot is packed with about half a million fine hairs, or setae. The tip of each hair has hundreds or thousands of projections, called spatulae, which measure about 10 millionths of an inch across and can get so close to a surface that weak interactions between molecules in the pad and on the surface become significant.
Prof Full's team deduced that the geckos exploit short-range atomic interactions, known as van der Waals' forces, by measuring the forces acting on a single seta during adhesion and disengagement. "These billion spatulae, which look like broccoli on the tips of the hairs, are outstanding adhesives," he said.
The van der Waals' forces used by the lizard are weak until surfaces get very close. When a large area is in contact, though, they can add up to a strong attraction.
A single gecko hair, only one 10th the diameter of a human hair, could lift an ant, and a million hairs covering an area the size of a 5p piece could lift a child of about 45lb. The combined force is a thousand times more than geckos need, so they can hang from a ceiling by one toe.
Since the mechanism works so well, the team has launched an effort to make a strong yet dry adhesive out of artificial hairs.