Soft Pneumatic Actuator from 3D-Printed TPU: Fabrication and Grasping Force Characterization

Soft pneumatic actuators providing infinite passive degrees of freedom are widely applied for safe physical human–robot interaction and fulfilling the limitation of conventional rigid structures. This paper presents a design of the soft actuator with pneumatic chamber enabling the control of bending and contact force. The actuator is solely fabricated from the thermoplastic polyurethane (TPU 95A) by using the fused deposition modeling (FDM) 3D printing. Several printing setups were performed for trial and error to prevent the air leak. The experimental setup was prepared for measuring the contact force in both vertical and horizontal directions. The grasping force varying against the input pressure ranged from 0 to 58 psi was studied at three contacting points along the longitudinal axis of the actuator with three different bending conditions. The stiffness of the actuator is related to the input pressure by considering the increase of total contacting force at different bending deformations. The results of this study can be applied to the stiffness control of soft pneumatic actuators.