Deformations of compliant textured surfaces due to surface stress

Protrusions or textures on a compliant solid surface will tend to deform, flatten, and develop rounded corners when the surface is in contact with a liquid or air. Considering initially rectangular ridges of height h and width w, this deformation has been studied experimentally and theoretically for nearly planar surfaces, where the aspect ratio is small, h/w << 1. We develop a microfabrication technique to produce compliant textures with large amplitude and extend these investigations to compliant textures with higher aspect ratio, h/w ~ 1. We experimentally measure texture flattening and rounding of sharp corners for two-dimensional ridges and three-dimensional pillars, and observe large deformations. We compare the results to previous theoretical predictions for low-aspect-ratio structures and comment on how the intial wavelength λ, height h, and width w change the amount of the final deformation. Finally, we discuss the implications for surface stress.