Spatially patterned stiffness variation in a light-triggered jumper for symmetry breaking and high snap-through efficiency

Abstract

The nonlinear strain response of soft material-based snap-through systems enables amplified and accelerated force output. However, efficiency of snap-through energy release is challenging to improve because of the inherent trade-off between initial curvature and stiffness. Here, spatial programming of stiffness variation in the azobenzene-functionalized liquid-crystalline polymer (Azo-LCP) addresses this limitation and achieves efficient photomechanical jumping. Introduction of stiffness mismatch induced localized curvature, which preserved the initial curvature and simultaneously enhanced photomechanical strain responsivity. By programming for symmetry of stiffness variation, we achieved directional or vertical jumping via strategic placement of the rigid region, with corresponding stress accumulation behaviors corroborated by finite element simulations. Integration of patterned stiffness variation with geometric asymmetry enabled both vertical and horizontal jumping within a single structure, without compromising performance. This dual-mode jumper also demonstrated sequential and consecutive jumps under continuous light exposure.