Superstrong Artificial Muscle Fibers with Dynamic Percolation Behavior

Stimuli-responsive soft materials with high compliance and adaptability are crucial for robotics, enabling intricate actuation and motion across challenging environments. Artificial muscles are essential in the progress of soft robotics, aiming to replicate the complex movements of biological systems. In this study, we introduce super-strong 'Hercules' artificial muscle fibers and bundles, which exhibit contractive actuation through an extrusion 3D printing technique. These fibers are designed with a composite structure that incorporates highly exfoliated graphene sheets into a stimuli-responsive liquid crystal elastomer matrix. The synergistic interaction among the fillers within the actuator matrix results in contraction with outstanding actuation performance, attributed to a dynamic percolation behavior of the fillers. This unprecedented behavior effectively strengthens the composite fibers and enables an electrical switching effect, particularly in the contracted state. Consequently, this represents the first instance of simultaneous actuation and real-time signal monitoring within a robust artificial muscle fiber, making it highly suitable for practical applications. Leveraging mechanically compliant structures, our artificial muscle fibers were seamlessly integrated into durable bundles and high-performance soft robotics.