SELF-FOLDING TRANSFORMER ROBOT BASED ON BIDIRECTIONAL SHAPE MEMORY POLYMER COMPOSITE ACTUATORS

Self-folding is universal in nature. The concept of self-folding has attracted interests from standpoints of both fundamental scientific research and technological innovations due to the advantages of self-folding over traditional manufacturing methods. Driven by the interests in self-folding, people have developed artificial self-folding structures at different length scales based on specific actuators that can realize unidirectional folding movement. To overcome the limitations of unidirectional actuators in fabricating more complex structures, people also developed actuators that can realize bidirectional folding action. Most of these actuators are based on shape memory effects of shape memory polymers and alloys. However, the applicability of these bidirectional actuators is restricted by drawbacks such as complexity in fabrication and programming. We have developed and characterized an easy-to-fabricate and low-cost shape memory polymer composite actuator which could enable bidirectional folding action with adjustable angles by simple programming procedures. Based on analytical, numerical, and experimental analysis, we have shown that we can control the folding angle and the folding force by adjusting the thickness ratio and/or the prestrain of the actuator. To demonstrate the potential application of the actuator, we reported a self-folding transformer robot which folds from two-dimensional (2D) sheet into three-dimensional (3D) configuration by itself and transforms between different 3D shapes via controlled heating of the actuators. Then, we presented the ability of the robot to do obstacle avoidance for practical applications. By combining findings from polymer science and robotics, we envision that the actuator can provide new opportunities for various applications including a soft robot that can transform its shape depending on surrounding environment and navigate itself