The range of motion of appendages - from macroscopic arms to microscopic cilia - critically determines their usefulness for accomplishing everyday tasks. The non-reciprocal stroke-like deformations and repeated twisting and bending in cilia, for example, are vital for controlled fluid transport and for microorganisms navigating their environment. Yet, the self-regulation necessary for such actuation behaviors has proven challenging to implement in synthetic microactuators. Despite recent advances in fabrication strategies and implementation of concepts from supramolecular and systems chemistry, the types of deformations achievable with microactuators remain limited. If microsctructures exhibit multimodal reconfigurations, such deformation behaviors are usually a result of multimaterial architectures, which are difficult to fabricate and control at the microscale. Herein, we report a new strategy to on-demand programmable, non-reciprocal, multimodal deformations of a simple single-material microstructure by deliberate symmetry breaking and implementation of an opto-chemo-mechanical feedback loop. High aspect-ratio microstructures fabricated from molding a photoresponsive liquid crystalline elastomer exhibit multiple types of deformations - including light-seeking, light-avoiding, and twisting - in case the material anisotropy is tilted away from the micropillar principal symmetry axis. These deformations can evolve to stroke-like deformations at higher light-intensity, at which propagation of light-activation throughout the pillar and (self-)shadowing effects regulate the deformation-trajectory. Such stroke-like trajectories are easily tailored and would be impossible to program by traditional composite architectures. Overall, the presented work offers a first foray into a vast design space of robust user-defined deformations and bodes well for adaptation in soft robotics and microfluidic devices.

Unusual but programmable self-regulated deformations in a single microstructure

ACS Spring Meeting 2021

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