Geckos interactions

Although any single van der Waals interaction is weak, a large number of van der Waals interactions creates a strong force. For example, geckos stick to walls and ceilings by van der Waals interactions of the surfaces with the 500,000 tiny hairs on each foot. 

Like a gecko, fimbriated bacteria use multivalent contacts for adhesion. Moreover, multivalency is a general theme in biological systems and multivalent interactions are of importance for numerous biological processes, such as immune... 

The role of frictional forces in adhesion has recently been re-examined, further exemplifying the complex mechanism of attachment in geckos. Conventionally, friction is described as a contact interaction between two surfaces that opposes their relative motion, thus preventing slippage. Friction at a macroscopic scale is proportional to, and depends upon, the normal force, which acts perpendicular to the surfaces, pushing them together. It also depends upon the coefficient of friction... 

Van der Waals-type interaction of every single seta with the substrate is a sufficient mechanism to explain the uncommon properties of gecko adhesive system. Van der Waals... 

In the hairy attachment system of the gekkonid lizards, van der Waals interactions are responsible for the generation of attractive forces (Hiller 1968 Autumn et al. 2000, 2002). Experiments, in which the force-displacement curves were determined for individual spatulae by atomic force microscopy, show that these smallest elements of the gecko s attachment system generate forces of about 10 nN O Fig. 54.5). An estimate of adhesion energy (y)... 

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