Fabrication and Self-sensing Control of Soft Electrothermal Actuator

Soft electrothermal actuators have attracted wide attention due to their high flexibility, adaptability and light weight. These characteristics give them great potentials to be used in biomimetic and soft robotics applications. In this paper, an electrothermal actuator with directly printed microfilament heater was designed, fabricated and characterized. The soft actuator used polyimide (PI) and polydimethylsiloxane (PDMS) as the structural materials due to their large mismatch of thermal expansion. A microfilament heater was electrohydrodynamic (EHD) printed using a low melting point alloy Bi58/Sn42, and embedded in-between the PI and PDMS layers. The fabricated actuator achieved a maximum curvature of 1.0 cm −1 under a supply voltage as low as 3 V. Resistive self-sensing technology was used to sense the deflection of the actuator and to develop the closed-loop control of the actuator. The bending curvature of the actuator is resulted from the temperature change of the actuator, which can be detected by the electrical resistance change of the embedded heater as they are linearly related. A PID controller was designed for the closed-loop operation of the actuator. Compared with the open-loop operation, the closed-loop controlled actuator demonstrated more rapid and precise response. The developed electrothermal actuator was successfully demonstrated for applications as a soft lifter and soft gripper.