Optimal Angles for Maximal Adhesion in Living Tokay Geckos

In this paper, we report experimental measurements of the adhesive angles of living Tokay geckos (Gekko gecko) at the two different characteristic sizes of the feet and toes. In particular, we have determined the adhesive angles between the opposing front and rear feet and between the first and fifth toe of each foot on different inverted surfaces [steel, aluminium, copper, poly(methyl methacrylate), and glass]. We rationalize the experimental results with the multiple peeling theory, recently derived, finding an interesting agreement; previous reported observations on the architecture of the gecko adhesive system, even at the size scale of the single seta, suggest the validity of the approach at different hierarchical levels.