Optimal Design of High-Aspect-Ratio Micro/Nano Hierarchical Structures Mimicking Gecko Foot-Hairs

Abstract

Geckos have extraordinary climbing ability. The multi-scale hierarchical structure of the gecko foot-hairs, especially the high-aspect-ratio structure of its micro-scale seta and nano-scale spatulae is the critical factor of the gecko’s ability to adopt and stick to any different surface with powerful adhesion force. In this paper, a series of models such as robust adhesion, easy detachment, rough surface adaption, anti-bunching and anti-fracture, have been proposed by simulating gecko’s attachment. Based on these models, we have launched a bottomup methodology for designing the high-aspect-ratio hierarchical structure mimicking gecko’s dry adhesive pad. A skillful procedure is also developed here to find out optimum parameters by multi-object optimization, including the hierarchical structural dimensions, the density and pattern of the fibers, and the geometric parameters of the single fiber. The outcome illustrates that the optimal designed parameters of the structure are analogous to those of geckos observed. Especially, the simulated adhesion force of the structure is consistent with the measured value of a single seta, which proves that the optimized structure also has powerful adhesive ability like geckos.