Wrinkle-free membranes through spatioselective exposure.

• A theoretical model is developed to estimate the wrinkling capabilities of stiffness-modulated membranes. • A wrinkle-free technique through stiffness modulation is proposed with neither area loss, weight increase nor interfacial delamination. • An easy-to-implement robust empirical wrinkle-free approach is provided. The extreme flexibility-induced wrinkling significantly hampers the promising engineering applications of membranes, while the existing wrinkling-suppression approaches have challenges for area loss, weight increase and interfacial delamination. Here we propose a facile wrinkle-free technique that enables stiffness modulation through spatioselective ultraviolet (UV) exposure, regulates stress distribution to eliminate compressive stresses and achieves robust wrinkle-free membranes. A small-deformation theoretical model with the Marguerre function is implemented to evaluate the wrinkling capability of a stiffness-modulated membrane, the non-gradient particle swarm optimization (PSO) algorithm is performed to obtain the optimal material distribution, and the related robust wrinkle-free performance is verified through both finite-deformation post-buckling analyses and physical experiments. In addition, an empirical wrinkle-free solution is also given without the requirement of excessive optimization. This wrinkle-free approach, with neither area loss, weight increase nor interfacial delamination, provides useful guidance for the research on wrinkle-free membranes. [Display omitted] [ABSTRACT FROM AUTHOR]