Reversible Surface Patterning by Dynamic Crosslink Gradients: Controlling Buckling in 2D

Harnessing the self‐organization of soft materials to make complex, well‐ordered surface patterns in a noninvasive manner is challenging. The wrinkling of thin films provides a compelling strategy to achieve this. Despite much attention, however, a simple, single‐step, reversible method that gives rise to controlled, two‐dimensional (2D) ordered, continuous, and discontinuous patterns has proven to be elusive. Here a novel, robust method is described to achieve this using an ultraviolet‐light‐sensitive anthracene‐containing polymer thin film. The origin of the patterns is the local buckling of the thin film, where the control over the topology is given by laterally patterning out‐of‐plane gradients in the crosslink density of the film. The underlying buckling mechanics and formation of the surface features are well‐described by finite element analysis. By illuminating the film with a photomask, local and long‐range patterns that can be both continuous and discontinuous are able to be written. Furthermore, the patterning is fully reversible over multiple cycles. The results demonstrate a simple strategy for erasable storage of information in a surface topography that has applications in memory, anticounterfeiting, and plasmonics.