Self-Healing Yet Strong Actuator Materials with Muscle-Like Diastole and Contraction via Multilevel Relaxations

Skeletal muscles represent a role model in soft robotics featuring agile locomotion and incredible mechanical robustness. However, existing actuators lack an optimal combination of actuation parameters (including actuation modes, work capacity, mechanical strength, and damage repair) to rival biological tissues. Here, a biomimetic structural design strategy via multilevel relaxations (α/β/γ/δ-relaxation) modulation is proposed for mechanical robust and healable actuator materials with muscle-like diastole and contraction abilities by orientational alignment of dendritic polyphenol-modified nano-assembles in eutectogels. The anisotropic hierarchical micro-nanostructures assembled by supramolecular interaction mimic the relative slippage of actin filaments and myosin in muscles, ensuring bistable actuation through rapid thermal α-relaxation and expansion. Furthermore, kinetically active secondary β/γ/δ-relaxation at reconfigurable interfaces can conquer the limited self-healing ability of fixed-orientation polymeric chains. The obtained artificial muscle exhibits high output actuation, robust mechanical properties (tensile strength of 33.5 MPa), and desired functional, mechanical self-healing efficiency (89.7%), exceeding typical natural muscles in living systems. The bionic micro-nano design strategy achieves bottom-up cooperative relaxation modulation to integrate all-round performance of natural muscles, which paves the way for substantial advancements in next-generation intelligent robotics.