Spatiotemporal Analysis of Intrinsically Curved Photomechanical Fibers

Abstract This paper investigates the effect of intrinsic (built-in) bending curvature on the dynamics, energetics, and stability of photomechanical fibers, which deform in response to illumination. We develop a multiphysics dynamic model based on the nonlinear Kirchhoff's rod theory to capture the coupled photomechanical response of the curved fibers. Using two canonical examples—the bending of a clamped-free strip and the periodic flapping of a clamped–clamped strip—we demonstrate how intrinsic curvature fundamentally affects the spatiotemporal deformation of the strips subject to steady illumination. Our findings reveal that the dynamic behavior of intrinsically curved photomechanical fibers differs both qualitatively and quantitatively from their intrinsically flat counterparts, underscoring the importance of initial geometry in the design and control of photomechanical systems. In particular, in the case of the clamped–clamped strips, although both the prestressed strip and stress-free curved strip exhibit self-sustained periodic flapping motions when subject to steady illumination, the stress-free curved strip requires higher input energy (i.e., greater light intensity), oscillates at a lower frequency, and exhibits a largely asymmetric deformation pathway per cycle. Moreover, the range of illumination angles that can trigger self-sustained oscillations in stress-free curved strips is narrower compared to the prestressed case.