Geckos suckers for walking on walls

Scientists in California have discovered why geckos can do the things they do, with implications for robot and remote-controlled appliance design.

Scientists at the Poly- PEDAL (Performance, Energetics, Dynamics, Animal Locomotion) Laboratory at the University of California, Berkeley, have made an important breakthrough in learning how geckos are able to stick to walls with such apparent ease.

Professor Full and his team now believe that the ‘stickiness’ of the gecko can be attributed to intermolecular forces so weak that they are normally swamped by the legion of strong natural forces, but which are nevertheless responsible for the attraction between layers of graphite, or that between enzymes and their substrate.

These intermolecular forces come into play because the gecko foot hairs get so close to the surface, allowing a billion spatulae to create a strong adhesive force. Calculations have shown that Van der Waals forces (those arising when unbalanced electrical charges around molecules attract one another) could explain the adhesion, possibly in conjunction with water adsorption.

If the human hand had the equivalent ‘sticking power’ it could lift weights disproportionate to both its size and normal conventions of lifting and ‘picking up’. With something approximating the geckos densely packed fine hairs, or ‘setae’ (up to half a million on each foot) and the weak attraction that molecules have for one another when they are brought very close together, the humble human hand could lift weights of up to 40 kilos.

The discovery may trickle down into the realms of engineering design. The Berkeley team are already working on a mechanical gecko which Professor Full hopes will lead to the discovery of a new, synthetic, dry adhesive.