Geckoes

A prime example of the impressive nse of adhesion in nature is the gecko, which can hang from the ceiling and climb with ease np smooth vertical surfaces (Fig. 20a). Its ability to do this was known for some time to be associated with the many thousands of hairs (or setae) comprising each foot (Fig. 20b). In addition, each seta was found to con-... 

FIG. 20 (a) Tokay gecko with toe outlined, (b) SEM of rows of setae, (c) The finest terminal... 

Smeets, W.J.A.J., J. Perez-Clausell, and F.A. Geneser. 1989. The distribution of zinc in the forebrain and midbrain of the lizard Gekko gecko. Anat. Embryol. 180 45-56. 

Edited by Eva Fairnell Production by Kathryn Botterill Design by Gecko Ltd Illustrations by Gecko Ltd Cover design by Susi Martin-T ylor Printed and bound by Scotprint... 

Autumn, K., Liang, Y. A., Hsieh, S. T., et al. (2000). Adhesive force of a single gecko foot-hair. Nature 405 681-685. 

R. Roll, Carotenoid and retinoid - two pigments in a gecko eye lens. Comp. Biochem. Physiol. A Mol. Integr. Physiol. 125 (2000) 105-112. 

Dial, B. E., Weldon, P. J., and Curtis, B. (1989). Chemosensory identification of snake predators [Phyllorhynchus decurtatus) by banded geckos [Coleonyx variegatus). Journal of Herpetology 23,224-229. 

Greenberg, B. (1943). Social behavior of the western banded gecko, Coleonyx variegatus Baird. Physiological Zoology 16,110-122. 

Mason, R. T. and Gutzke, W. H. N. (1990). Sex recognition in the leopard gecko, Euble-pharis macularis (Sauria Gekkonidae). Possible mediation by skin-derived semio-chemicah. Journal of ChemicalEcology 16,27-36. 

Gao Liang Jiang (Alpiniae officinari rhizoma) Ge Jie (Gecko) ... 

The greater the surface area the greater the number of induced dipole-induced dipole forces of attraction that can occur between the gecko s foot and the surface, such as the underside of a leaf or a wall or ceiling. 

Figure 6.2 Picture of a gecko foot (left) and scanning electron microscope images of different resolution of setae (middle) and spatulae (right). Images were kindly provided by K. Autumn.

Geckos, and maybe ladybugs, crawl on ceilings by van der Waals attraction. The adhesive force of a gecko foot hair or "seta" to a silicon surface is of the right magnitude to... 

Unless your in-laws are physicists, you probably won t find much here for the next family reunion. However, if van der Waals forces do come up, tell the kids about geckos and ladybugs. Try to protect the children from the kind of 1930s concepts and modern elaborations that they are likely to have picked up from timid teachers or dumbed-down texts. Even if many of its instructors still work with outmoded ideas, the next generation need not be afraid to flex the muscle of modern physics. 

Geckos, Aristotle observed more than 2,000 years ago, can "run up and down a tree in any way, even with the head downwards." Actually, they can do far more astounding things than that. 

Geckos can stroll across a plaster ceiling or hang upside down from a polished glass surface using only one foot. Geckos, it seems, can stick to almost any surface, rough or smooth. To understand how they do it, one needs to know a bit more about them. 

---