Abstract

I will introduce two instabilities that occur in highly elastic layers. In the first the layer is confined between and bonded to two rigid bodies which are then separated. At a critical separation fingers of air protrude into the elastic layer from its boundary in a way reminiscent of Saffman-Taylor fingering in confined viscous fluids. In the second the elastic layer is bonded to a rigid substrate and then caused to grow (or swell). The growth leads to substantial compression on the free surface and, at a critical degree of compression, the surface develops sulci. I will explore the patterns formed by these sulci and explain why the transition to the sulcal state has so far eluded theoretical explanation.