Light-induced wrinkling in annulus anisotropic liquid crystal elastomer films

Liquid crystal elastomer (LCE) films deform under external stimuli showing significant potential in smart structures and flexible sensors. Due to the small out-of-plane stiffness of LCE films, wrinkling instability poses a critical challenge for the application of LCE films. Different from previous studies, we utilize the anisotropy constitutive model to investigate light-induced wrinkling instability in annulus LCE films with an internal hole. The degree of anisotropy in light-sensitive LCE is determined by two parameters: the anisotropic ratio (ratio of the elastic modulus) and the spontaneous strain ratio. Liquid crystal directors align radially, causing in-plane radial shrinkage and expansion in the other directions under light radiation. Using linear perturbation analysis, we study the critical conditions and wrinkle numbers for the onset of wrinkling instability. Our findings reveal that annulus LCE films with anisotropy exhibit a higher number of wrinkles upon instability. We present the phase diagrams of flat or wrinkled states illustrating the condition under which the film remains flat or transitions into a wrinkled state. This behavior depends on anisotropic parameters, light intensity, contraction coefficient, hole size, and film thickness. By adjusting the combination of these parameters, one can control the wrinkling instability of LCE films. Furthermore, we show that the critical time for the onset of wrinkling decreases as the light intensity and contraction coefficient increase. The findings from this work can provide references for the design of smart structures based on light-sensitive LCE films.