Biological and artificial attachment devices: Lessons for materials scientists from flies and geckos

In insects, spiders, and geckos, adhesion to surfaces is mediated by finely structured contact elements. We have studied the structure and function of these elements on the micro and nano level by microscopical and nanomechanical techniques. Local mechanical properties and adhesion forces are measured by novel test methods and compared with predictions based on theoretical contact mechanics. Structure, size and shape of the contact elements are found to play important roles; in particular the principle of “contact splitting” has been identified: finer contact elements (down to sub-micron level) produce larger contact forces in heavier animals. The insight gained in studying biological systems can be transferred to the development of optimized artificial attachment devices. From our findings, the desired mechanical parameters of attachment structures can conveniently be delineated in newly developed adhesion design maps. Based on these investigations, a clearer strategy for producing optimum bio-inspired attachment structures is beginning to emerge. This paper gives an overview of our recent work in theory and experimental measurement of such adhesion phenomena.