Effect of the Orientation and Bending Stiffness of Nanopatterned Films on Wrinkling

The production of hierarchical structures has an important role for applications such as superhydrophobic surfaces, structural colors, and energy devices. Microscale wrinkling of surfaces decorated by nanoscale patterns can be one of the most efficient methods to realize hierarchical structures. Here, we investigate wrinkling of films embedding anisotropic nanopatterned surfaces prepared by nanoimprint lithography. After transferring nanoimprinted polystyrene thin films onto stretched elastomeric substrates, we achieve microscale wrinkles by releasing the strain. We examine the anisotropic wrinkles of well-defined nanolines with various widths, heights, and spacing ratios and propose a model that considers only bending stiffness of the patterned film. We compare the approach with a model that considers inplane stiffness and confirm that our scheme matches well with that of nanopatterns with thin residual layers. [Figure not available: see fulltext.].