Drying patterns in a confined hyperelastic hydrogel

In many constraint systems, from paintings to muddy soils, the evaporation of a solvent leads to the formation of complex drying patterns. Commonly these patterns are characterized by brittle straight cracks. Here, we report very different structures that emerge during the drying of thin films of hyperelastic hydrogels confined between two glass plates. The evaporation front advances by intermittent bursts, leading either to a growing front of bubbles or finger-like structures. We discuss how these morphologies result from the interplay between the drying-induced flow inside the gel and the gel’s non-linear elasticity.