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Shape Memory Polymer-based Stiffness Variable Soft Actuator Via Digital Light Processing-based 3D Printing

Variable stiffness actuators have the ability to change stiffness while retaining the advantages of soft actuators, it can be used in an environment requiring a large load. There are many materials used in variable stiffness actuators, among which shape memory polymers (SMP) can change from glassy state to rubber state under temperature change, and its modulus can realize large-span change. At the same time, shape memory polymers under the acrylic acid system have good 3D printable characteristics, so it is more suitable as variable stiffness material. Many researchers have used SMP to make variable stiffness actuators. However, the method of making these reports includes multiple steps, which is very time-consuming and requires high equipment. Our team recently reported a variable stiffness actuator based on digital light processing 3D printing technology (DLP), which can be printed using commercial printers or self-built printers. The variable stiffness layer and actuator cavity can be manufactured by DLP printing technology. At the same time, the materials used can be commercially purchased. The scheme of preparing polymer precursors is very friendly to users without chemical background. The method proposed in this study can quickly and conveniently fabricate variable stiffness actuators based on shape memory polymers.