27.3 Friday, Jan. 4 Gecko toe and lamella adhesion on macroscopically rough surfaces GILLIES, A G*; LIN, H; HENRY, A; REN, A; SHIUAN, K; FEARING, R S; FULL, R J; University of California, Berkeley email@example.com
The role in adhesion of the lamellae and toes - intermediate sized structures - found on the gecko foot remains unclear. Insight into the function of these structures can lead to a more general understanding of the hierarchical nature of the gecko adhesive system, but in particular how environmental topology may relate to gecko foot morphology. We sought to discern the mechanics of the lamella and toes by examining gecko adhesion on controlled macroscopically rough surfaces. Live Tokay geckos, Gekko gecko, were used to observe the maximum shear force a gecko foot can attain on an engineered substrate with sinusoidal patterns of varying amplitudes and wavelengths in sizes similar to the dimensions of the lamella and toe structures (0.5 – 6 mm). We found shear adhesion was significantly lower on surfaces that had amplitudes and wavelengths approaching the lamella length and inter-lamella spacing, losing 95% of adhesion over the range tested. We also found that the toes are capable of adhering to surfaces with amplitudes much larger than their dimensions even without engaging claws, maintaining 60% of adhesion on surfaces with amplitudes of 3 mm. Results suggest that gecko adhesion may be predicted by the ratio of the lamella dimensions to surface feature dimensions, and that macroscopic-scale features are necessary to maintain contact, and consequently, generate adhesion on macroscopically rough surfaces. Findings on the larger scale structures on gecko feet could provide the biological inspiration to drive the design of more effective and versatile synthetic fibrillar adhesives.