LAUSR

Introducing roughness features onto materials' surface can serve as an efficient strategy for novel or enhanced surface functionality. Surface roughness can be developed spontaneously on exponentially growing polyelectrolyte multilayer films without any postassembly treatment. This is essentially a pressure‐induced wrinkling behavior, which is associated with the diffusion of polyelectrolyte chains into the films during the assembling process. Here, this wrinkling behavior is suppressed by applying a pre‐cross‐linking process, which can produce steric hindrance within the films against the diffusion of oncoming polyelectrolytes. With the aid of photolithography, the wrinkling behavior can be “turned off” regioselectively and confined on the areas unexposed to UV irradiation, thus leading to a film with patterned surface wrinkles and paving the way for novel applications.