Pulsating self-snapping of a liquid crystal elastomer bilayer spherical shell under steady illumination

Abstract

Self-oscillation can absorb energy from constant external environment to maintain its own continuous motion, and has potential application in the fields of soft robotics, motors, military industry and so on. Inspired by the intermittent predation of Venus fly-trap, we creatively develop a pulsating self-snapping system in this paper, which is composed of liquid crystal elastomer (LCE) bilayer spherical shell under steady illumination. Based on shallow shell theory and dynamic LCE model, a nonlinear dynamic model of self-snapping shell is formulated. Through quasi-static analysis, the self-snapping of LCE bilayer shell under steady illumination is investigated by utilizing the modified iteration method. The LCE bilayer shell under steady illumination can develop into two motion regimes, namely the static regime and the self-snapping regime. The snapping-through of bilayer shell results from the light-driven bending moments tending to flatten the shell, and the self-snapping can be maintained by transforming between snap-through in illumination zone and snap-back in dark zone. In addition, the critical conditions for triggering self-snapping, and its energy release ratio are investigated in detail. Different from the existing abundant self-oscillating systems, this self-snapping system has advantages of large displacement, rapid energy release and high energy release ratio, and may pave a new way for the development of jumping robotics, actuated devices, military industry and so on.