Humidity‐Driven Dynamic Based on Polystyrene‐Contained Gelatin (Gel‐PS) and PDMS Bilayer Wrinkling System

Abstract Hierarchical stimuli‐responsive surface pattern, which can realize the responsive surface with the dynamically tunable structures and on‐demand properties, is the key to realize smart materials and devices, yet its fabrication remains challenging. This study presents a simple and robust fabrication strategy for creating a dynamic hierarchical surface wrinkle using a bilayer wrinkling system. This system consists of a hard and thin skin film made of gelatin containing polystyrene (PS) particles and a soft and thick substrate of polydimethylsiloxane. Based on the buckling deformation caused by stress instability in bilayer wrinkling system, the hierarchical surface wrinkles with random distribution of PS microparticles can be realized. By controlling the humidity in the environment and leveraging the different sensitivity of the exposed regions with high modulus and the soft unexposed regions, various dynamic hierarchical structures can be achieved. This wrinkled surface is a promising candidate for applications such as dynamic displays, optical smart windows, and anti‐counterfeiting due to the strong light scattering effect of the surface wrinkles.