Hysteretic Behavior in Responses of Microwrinkle Patterns to Mechanical Strain

Abstract

Surfaces of some compliant materials, whose surface layers are harder than the bulk, sometimes form wrinkles with a stripe pattern. The wrinkles have potential impacts on the nanotechnology because the spatial wavelength can be small as submicron scales. The microwrinkles can rearrange in response to the mechanical perturbation, e.g., compression. Here, we focus on a hysteretic behavior of the microwrinkles under a slow cycle of compression and decompression. The local stripe directions change to the compression direction one after another as compression proceeds. However, the stripe patterns upon compression are different from those upon decompression, showing hysteresis in the pattern. We propose a simple phenomenological model that resembles Ising spin models, to understand the basic mechanism of the hysteretic behavior. The model suggests that the hysteresis in the pattern can be caused by the direct coupling between elements.