2D Skeletal Muscle Thin Film Actuators Enhance Efficiency of Biohybrid Robots

ABSTRACT Biohybrid robots actuated by living skeletal muscles are capable of adaptive functional behaviors and could enable future applications ranging from precision microsurgery to unmanned exploration. Skeletal muscle‐powered robots typically rely on 3D tissues which require large cell volumes and offer limited control of muscle fiber alignment. Here, we present a method for fabricating 2D monolayers, or thin films, of skeletal muscle on micropatterned hydrogel skeletons. We vary skeleton design parameters to optimize fiber alignment and resultant actuation forces and strokes. Our optimized designs generate mN‐scale forces and mm‐scale force strokes from cm‐scale tissues, significantly outperforming previous 2D skeletal muscle actuators and improving untethered longevity by ∼4500× from < 10 min to > 30 days. Moreover, such thin films increase force density (contractile force per unit tissue volume) by 20X as compared to 3D muscles, thus significantly increasing efficiency. We leverage optimized skeletal muscle thin films to power a multi‐limbed robot with independent fins capable of on/off and frequency‐dependent speed control. With these control inputs, we achieve steered multi‐directional locomotion at speeds up to 4 body lengths per minute in straight movement and 1200 degrees per minute in rotational movement, highlighting potential for such actuators to power long‐lasting functional robots.