A Flexible, Architected Soft Robotic Actuator for Motorized Extensional Motion

To advance the design space of electrically-driven soft actuators, a flexible, architected soft robotic actuator is presented for motor-driven extensional motion. The actuator comprises a 3D printed, cylindrical handed shearing auxetic (HSA) structure and a deformable, internal rubber bellows shaft. The actuator linearly extends upon applying torque from a servo motor; the rubber bellows shaft is stretchable but resistant to torsional deflection, allowing it to transmit torque from the servo motor to the other end of the HSA. The high flexibility of the HSA and rubber bellows shaft enable the actuator to adaptively extend even when bent. The actuator's two components and its performance are mechanically characterized. Actuation strains of 45% elongation and a maximum blocked pushing force of about 8 N are demonstrated. The actuator's capabilities are showcased in two separate demonstrations: a crawling robot and a sensorized artificial muscle that integrates a microfluidic, liquid metal strain sensor. The architected material design approach for a robust, motor-driven soft actuator provides several unique features—including a compact form factor and ease of use—over other motorized soft robotic actuators based on HSA assemblies or cable tendon mechanisms.