Harnessing multimodal wrinkle patterns in flexible films by three-axial mechanical loading

Controllable wrinkle structures have great application prospects in the fields of flexible electronics, smart sensing, elastic optics, surface wetting, and bio-interfaces. In flexible film-substrate systems, strain actuation is capable of obtaining various wrinkle patterns with single morphological features including labyrinths, herringbones, stripes, hierarchies and ordered arrays. However, it is still a big challenge to obtain multiple wrinkle patterns on a surface of film simultaneously. Here, we propose a facile method for preparing controllable multimode wrinkles by exerting three-axial compression. The morphological features of the wrinkles show a universal position-dependent behavior for different flexible film systems. From a corner of the triangular film sample to the opposite edge, the wrinkles evolve from striped structure to labyrinth-like structure and finally to rippled structure gradually. The finite element simulation and stress theory well explain the formation mechanism and evolution behavior of the multimode wrinkles observed in experiments. The surface friction and light diffraction are strongly dependent on the wrinkle features and show excellent reversibility and stability by cyclic mechanical loading. This work can promote better understanding of stress distribution and wrinkling mechanism under three-axial mechanical loading, and can develop a novel technique for preparing controllable multiple, position-dependent wrinkle patterns.