Programmable wrinkling patterns of liquid crystal network bilayers on compliant substrates

Smart soft materials have gained increasing attention in recent years because of their adaptive behaviors to external multi-physics stimuli, enabling diverse applications across multiple fields. Here, we show programmable wrinkling morphological patterns on liquid crystal network (LCN) bilayers bonded to compliant substrates under thermal load, by tuning the orientation of directors between LCN bilayers. We propose a solid-shell formulation that merges enhanced and natural assumed strain approaches to investigate the pattern formation and morphological transition of LCN bilayers. By introducing director-determined anisotropic spontaneous strains, we explore effects of director orientations determined by two angles (in-plane) and (out-of-plane) for each layer, on surface wrinkling pattern formation and evolution. When the directors are aligned in-plane, oblique angles of stripe wrinkles approximates to the average value of director angles in LCN bilayers. For more general spatial alignments of directors, phase diagrams on wrinkling modes indicate that diverse morphologies such as stripe, checkerboard, herringbone and parallel bead-chain modes, can emerge due to intricate nonlinear interactions between bilayers. Pattern selection is found to be primarily determined by the in-plane angle, rather than the out-of-plane angle. Our results could offer valuable insights into the functional design of smart surfaces related to wrinkling morphology.

Yifan Yang, Shichen Zhao, Zhijun Dai, Fan Xu*

Int. J. Solids Struct. 309, 113206, 2025. http://doi.org/10.1016/j.ijsolstr.2024.113206