Design and Characterization of a Soft Flat Tube Twisting Actuator

Soft actuators have shown advantages of adaptiveness, large deformation, and safe human-robot interaction, making them suitable for various applications. Herein, a novel soft flat tube twisting actuator (SFTTA) is proposed. The SFTTA is composed of a folded flat tube sandwiched between two silicone rubber laminates. When inflated by compressed air, the folded corners of the flat tube tend to unfold, resulting in the twist of the actuator to a helical structure. The SFTTA has great scalability. It can be fabricated through simple processes with low-cost materials. For a sample SFTTA with the size of a human finger, it can twist 540⁰ at an air pressure of 300 kPa. In general, SFTTA based actuators can twist 9.6 degree per millimeter in length, which is significantly larger than previously reported soft twisting actuators. Additionally, the composite-like SFTTA allows mechanical property programming through the alteration of folding patterns of the flat tube and the material structure of the elastomer laminates. Finally, an extensible soft gripper based on flat tube actuators and a robotic wrist module are developed, and their rotation is realized by the proposed SFTTA actuator.