3D‐Printed Actuator Powered by Liquid Crystal Elastomer Muscles at the Water–Air Interface

Soft robots capable of safe, adaptable interactions in unstructured environments require actuators that are responsive, durable, and versatile. Liquid crystal elastomers (LCEs) meet these criteria, offering large, reversible deformations when stimulated thermally or optically. Here, we develop a direct ink writing approach to fabricate LCE‐based actuators integrated with passive polydimethylsiloxane (PDMS) components, enabling remotely triggered motion at the water‐air interface. We first tune mesogen chemistry, thiol linkers, and oligomer chain length to achieve printable inks with low viscosity and transition temperatures below 80 °C. Rectangular actuators are 3D printed from optimized LCE precursor inks with incorporated graphene oxide sheets for near‐infrared (NIR) photothermal actuation with high reproducibility and reversible bending. Embedding these muscle‐like elements into PDMS structures yields biomimetic whale‐like soft robots exhibiting undulatory locomotion. Alternative ink formulations allow for coordinated linear contractions of the resulting LCE units enabling a frog‐inspired surface swimmer with six LCE‐based muscles triggered by NIR light. We demonstrate how molecular design and multimaterial 3D printing can be combined to produce untethered, light‐responsive soft robots with controllable locomotion, expanding the design space for soft robotic systems in aquatic and amphibious environments.