Abstract:

Bioinspired micropillar-arrayed surfaces have been widely adopted across diverse applications because they enable tunable adhesion enhancement. Although prior studies have examined their load-sharing efficiency and adhesion enhancement, the rate-dependent effects remain largely unexplored. Here, we investigate the rate dependence of the load-sharing efficiency and adhesion enhancement by extending an elastic array model to the viscoelastic case through the Lee-Radok correspondence principle. Our results show a pronounced drop in the load-sharing efficiency at intermediate loading rates, which can be attributed to a reduced effective stiffness ratio between the backing layer and the micropillars, leading to a larger count of deformation accommodated by the backing layer. The extent of the intermediate-rate reduction scales positively with the array size, and decreases with the increasing pillar spacing and pillar length. In terms of adhesion performance, the array designs that enhance adhesion relative to a smooth interface in the static limit do not necessarily retain this advantage once the rate effects are considered. This degradation is particularly pronounced for the dense arrays of slender micropillars, for which the maximum pull-off force ratio relative to a smooth surface can drop much more markedly than in the quasi-static case, thereby necessitating careful evaluation. The findings provide guidance for the design and reliability assessment of bioinspired micropillar interfaces under rate-dependent loading conditions.

Key words: micropillar-arrayed surface, rate effect, load-sharing efficiency, adhesion performance