Design and Manufacturing of Electrically Driven Soft Actuators and Robots based on Liquid-Vapor Phase Transition

Abstract

In this dissertation, the possibilities of designing and manufacturing soft actuators utilizing liquid-vapor phase transition are proposed and examined. The first part begins with describing the basic concept and working principle of soft pouch actuators based on phase change fluid and a theoretical model is explained to predict deformation and force including a silent actuation as well as compact size and lightweight. Due to these advantages, soft pouch actuator is the applicable for the various applications operated in the cramped or complex environment. The pouch actuator design is extended from a rectangular shape to a stackable square shape to broaden the ability. In addition, several strategies to improve pouch ability were introduced. Thereby, a series of performance evaluations were conducted to verify the capability of pouch actuators. In the second part of the dissertation, based on the proposed pouch actuator’s merits, various robotic applications were demonstrated. As a first application, the concept of a single pouch actuator was utilized to create a bioinspired soft swim bladder which can achieve buoyancy control functionality. The soft buoyancy control mechanism is integrated with SMA actuator, which can generate double side bending motion, to form the robotic fish. The robotic fish presented its capability of achieving effective depth control and swim performance. Another robotic application was demonstrated a piston-like soft mechanism based on reversible pouch expansion and contraction behavior. The soft robotic piston is constructed by simple assembling stacked multiple soft pouch actuators, that can be used as the power sources in a wide range of robotic applications. By combining modularized soft piston with the other functional components, the bio-inspired robotic grippers and walking robot were designed and realized. In the final part, a new method based on 3D printing technology for fabricating a soft pouch actuator with multifunctional electric elements is proposed. This fabrication method is utilized to 3d print the soft pouch actuator with a resistance heating circuit and sensor trace with multiple printing materials. 3D printing-based manufacturing can produce a 3D object with complex geometry rapidly and easily. To verify this, the LEGO-like stackable soft actuator is demonstrated. This concept is then advanced to construct a 3d printed soft gripper that can generate a multi-bending curvature with individual actuation design, as well as grasping various objects with different size, shape, and stiffness.