Resilience of hierarchical actuators highlighted by a myosin-to-muscle mock-up

Skeletal muscle is the main actuator of various families of vertebrates (mammals, fish, reptiles). It displays remarkable robustness to micro-damage, that supposedly originates both from its redundant hierarchical structure and its nervous command. A bioinspired mock-up was designed and manufactured mimicking sarcomeres (micro-scale) and its series and parallel structure from fibre to muscle. First, the mechanical performances namely the force-velocity curve of the intact muscle mock-up were measured and modelled. Then, mimicking micro-damage by making some myosin heads inoperative, the mechanical performances were again measured to determine the resilience of the actuator. The mock-up is shown to be resilient: in the event of 10% damage of the mock-up, the mechanical performance of the mock-up was around 80% of the intact one. In this multi degrees of freedom actuator with hierarchical structure, the resilience is shown to be almost linear with the damage level for uniformly distributed damage (both maximal force and velocity decrease). Differently when micro-damage are clustered on a fibre, this decreases the maximal force with little effect on velocity.