Soft materials for soft robots

Comparing with traditional robotic design based rigid materials, soft material based robotic design shows unique advantages such as large deformation and great compatibility for many applications such as human-machine-interfaces. The field of soft robotics has witnessed numerous growths of new designs of soft actuators and soft sensors. Even though they show the great uniqueness of using soft materials but many of them do not have a comprehensive performance to adapt to different complex scenarios. Therefore, we came with material-level designs using soft smart materials, such as liquid crystal elastomers and hydrogels, to address this challenge. In this dissertation, we first designed and fabricated an electrically controlled soft actuator with multiple and reprogrammable actuation modes, and then demonstrated a reusable and general-purpose soft actuator which can meet various requirements in constructing new soft active devices. Secondly, we developed an integrated artificial motor unit based on gold-coated ultrathin liquid crystal elastomer (LCE) film. Due to the small thermal inertial of the ultrathin LCE structure, its cyclic actuation speed is fast and easily controllable. We showed that under electrical stimulation, the actuation strain of the LCE-based motor unit reaches 45%, strain rate is as high as 750 %/s, and the output power density is as high as 1360 W/kg. Lastly, we developed a transparent and stretchable hydrogel-based ionic diode based on doped polyacrylamide hydrogels. Using the ionic diode, we further successfully constructed two types of ionic logic gates, which can potentially be used as soft sensors. We hope the material-based designs of soft actuators and soft sensors we developed in this dissertation can be used as the basic functional elements for advanced and integrated soft robotic systems