Architected Soft Actuators for Artificial Musculoskeletal Systems

Vertebrates depend on their musculoskeletal system for locomotion, manipulation, interaction with their environment, and more. The robustness and efficiency of animal locomotion are difficult to achieve in robots because their hardware does not replicate the mechanics and performance of animal bodies. Moreover, many state-of-the-art soft actuators are ill-suited as muscles in artificial musculoskeletal systems for deployable, task-capable robots. This study presents an electrically-driven, architected soft actuator that can be assembled into artificial musculoskeletal systems. The fully 3D printed actuators linearly extend and contract through the rotation of an integrated servo motor. They comprise a thermoplastic polyurethane handed shearing auxetic (HSA) and origami bellows structure. Together, these structures transmit torque, stretch, and resist torsional deflection in a manner that produces large linear actuation and force output up to 59 mm (or 30% strain) and 75 N, respectively. It showcases the actuator's performance as artificial muscles in a battery-powered, human-scale leg that can use three muscles to kick a ball. When accounting for the weight of auxiliary hardware, the actuators exhibit power and energy densities that are four orders of magnitude higher than for leading soft artificial muscles. The soft actuators represent a step toward providing robots with bioinspired musculoskeletal systems for animal-like abilities.