Pattern formation in elastic bilayer systems through substrate pre-stretching

Compressing a thin film bonded to an elastic substrate beyond a critical stress results in an elastic instability, often referred to as wrinkling or ruga, that generates complex surface deformation. Although the best-known example is the sinusoidal wrinkling that appears under uni-axial compression of the film, other loading conditions and actuation mechanisms result in a diverse range of self-organized patterns. We will present experiments in which the substrate is pre-stretched prior to the adhesion of the film, which when released results in film compression. We will show that with only moderate variations in the system and control parameters we can transition between a wide range of patterns, with a well-defined phase diagram spanning periodic wrinkles, creases, folds, and high aspect ratio ridges. We will also explore the dynamics that control the pattern formation, as well as the effect of repeated unloading and reloading, in an effort to rationalize how the specific details of the pattern are determined.