Thursday, June 05, 2008
Knowing my strange yet heartfelt obsessions, a friend sent me an article with a picture of a gecko's foot.
Gecko pads are made of hairs that are divided and subdivided and then subdivided again, so the end of the hair has been described as looking like broccoli. The result is a bunch of hair so fine that the attraction between it and say, a plate of glass, is based on Van der Waal's forces. These are electrical charges that only come into effect when two surfaces are infinitesimally close to each other. Although they only operate at these short distances they are very strong, so something small enough to take advantage of them can support a lot of weight. Gecko feet are uniquely built by these subdivisions to provide a lot of flat pads at the end for maximimum stick, and yet be thick enough in the hairs, bundles and plates that make up the pads to have strength that will support the animal. The result is a creature which can walk up vertical glass.
The "broccoli" description doesn't do it justice. Here is the picture, from the University of Kwazulu-Natal's alumnus newsletter.
The photo, by Tony Bruton and Vijay Bandu, won a prize in the university's Science Close-Up category.
One interesting effect of this arrangement is seen when a gecko is trying to be stealthy. Instead of tiptoeing on the tips of its toes, it curls its toes into the air, away from the surface and creeps by plunking along on the flats of its feet.