Dynamic Wrinkling of Geometrically Templated Poly(vinyl alcohol) Soap Films during Liquid-to-Solid Phase Transition

Wrinkles generated from dynamic buckling instability, compared to static wrinkling from materials mechanical properties mismatch, can offer a broader selection of attainable patterns due to the tunable material elasticity by environmental conditions such as humidity, temperature, and mechanical load. However, such dynamic wrinkling is often transient due to its formation on ephemeral liquid films or thin polymer sheets at interfaces. Here, we report a new method to fabricate long-lasting wrinkling patterns from the dynamic process of drying high molecular weight poly(vinyl alcohol) (PVA) soap films templated by 3D printed frames. The PVA soap films are highly stable on the frame without burst due to the extensive chain entanglement; the wrinkle patterns can survive the phase transition and remain stable after water evaporation. The correlations between wrinkle patterns generated and PVA molecular weight, concentrations, evaporation speed, and environmental humidity are studied. An analytical model is established and verified experimentally. Possibilities to locally control the winkle patterns on films of zero and negative Gaussian curvatures are demonstrated. This work may give insights to program patterns towards applications such as flexible electronics and biomedical devices.