Role of structural stiffness on the loading capacity of fibrillar adhesive composite

Bio-inspired fibrillar adhesives have been extensively studied for applications in a wide range of fields, including transfer printing, intelligent robotics, and space technology. Herein, by considering a generalized adhesive composite composed of a fibrillar adhesive layer and a backing layer in contact with a smooth substrate, we developed a theoretical approach based on the peel zone model to predict its loading and failure behavior. The effects of mechanical and geometrical properties were discussed and verified with finite element method simulations. We found that the loading capacity is dominated by the effective adhesion strength and the stretched area of the adhesive micropillars (peel zone) with a simple linear relationship. Specifically, the peel zone is determined by the ratio of the bending stiffness of the backing layer to the tensile stiffness of the micropillar structures. Moreover, a design map for desired loading capacity with optimized structural stiffness is proposed. These findings present a comprehensive understanding of the loading mechanism of fibrillar adhesives and provide new insights into the rational design of reversible strong adhesion for related technologies.