Fan-shaped electrostatic soft hydraulic actuator with enhanced pressure and robustness

The development of adaptable and flexible soft actuators holds significant potential in numerous fields, including medical devices, robotics, and industrial applications. However, despite their high output and rapid response, conventional hydraulic and pneumatic actuators face challenges (such as the rigidity of electromagnetic motor materials and limited installation flexibility for multiple degrees of freedom robots), which limit their use in mobile or wearable systems. Conversely, electrostatic actuators, particularly those employing the zipping principle, offer promising lightweight and efficient alternatives. This study introduces a fan-shaped electrostatic hydraulic actuator (FsEHA) designed to enhance pressure generation, reduce drive voltage, and provide stability regardless of the actuator orientation. Various configurations of the FsEHA were compared with a conventional rectangular actuator, examining the impact of geometry and internal welding lines on pressure generation and posture-dependent performance. The results demonstrate that the FsEHA with seven internal welding lines achieved a 1.9-fold increase in pressure change compared to the rectangular actuator, reaching 4.53 kPa at 6 kV. Furthermore, FsEHAs with three or more internal welding lines demonstrated stable performances across different orientations, unlike the rectangular actuator, which exhibited significant posture-dependent variability. These findings offer valuable design guidelines for soft electrostatic actuators, potentially contributing to advancements in fields such as medical instruments, robotics, and wearable technologies.