Suction effects of crater arrays

Abstract

There are emerging experimental evidence that craters engineered on polymer surfaces can enhance attachment via suction effects. In the past, we have developed a theoretical framework for quantifying suction forces produced by an isolated crater, i.e., a crater resides on the surface of a semi-infinite solid, under both dry and wet conditions. Following this framework, in this paper, we investigate the suction effects produced by an array of craters. As arrays of both cylinder-shaped (CS) and spherical-cap-shaped (SCS) craters have been reported in the literature, we first make a comparison between them and find that the SCS craters outperform the CS craters. Thereafter, we focus on SCS crater arrays and study the effects of area fraction as well as different types of array patterns (square vs. hexagon). Assuming a given polymer matrix, using finite element modeling (FEM), we find that for both patterns, when the preload is small, suction force increases with crater area fraction. However, when the preload is large (e.g., when the craters attain full closure), non-monotonic relationship between suction force and crater area fraction exists. This is because suction force is governed by not only the pressure drop but also the projected area of the crater after unloading.