Multiscale mechanics and physics of nature’s dry adhesion systems

Dry adhesion systems adhere via physical bonds without any significant contribution from a liquid medium. In nature, these systems are found among the footpads of spiders, lizards and many other small animals, with high adhesion force, low detachment force and elfcleaning properties. These features are highly interesting for biomimetic man-made adhesives. Heavy animals have an adhesion force much higher than its muscle force, and to enable detachment, they have evolved a functional surface with hair-like structures called setae. Each seta branches into numerous microcontact elements that interact with the contacting area. This thesis continue on previous work, analyzing the functional surface in terms of contact geometries and stress distribution, and considers, for the first time, the effect of thermal fluctuations. Numerical and analytical results show how the muscle force is concentrated to a small fraction of the adhesion area, where each microcontact element is trapped in a potential well. The rate of detachment depends on the maximal concentration of stress across the crocontacts. When a seta is axially loaded, the concentration of stress is minimized, whereas radial loading amplifies the concentration of stress by a factor of maximum 68 and enable detachment with the animal’s limited muscle force. The results give theoretical insight in the adhesion and detachment of a functional surface. This knowledge is valuable and can be considered when constructing man-made adhesives with inspiration from nature’s dry adhesion solutions