Electroactive Twisted Ribbon for Torsional Zipping Actuator

Electrostatic soft actuators are known for their high power, rapid response, and accessible control. A variety of operational modalities have been achieved in electrostatic actuators; however, torsional movement remains particularly challenging and has been rarely investigated. This letter employs the dielectrophoretic liquid zipping (DLZ) actuation principle to develop a compliant torsional mechanism. The actuator uses pre-twisted ribbons to achieve torsional deformation with axial contraction when subjected to an electrostatic zipping force. The effects of key parameters, including geometric design, loading constraints, and input voltage, are studied to improve the actuator's performance, including both displacement and force in torsional rotation and axial contraction. By selecting materials such as the length and thickness of the ribbons and controlling the applied voltage, the actuator's behaviour can be tuned for a range of desirable contractions and torsion, maximising one mode of actuation while minimising the other. Additionally, the dynamic response of the actuator under different voltage waveforms and frequencies is investigated. This study extends the design capabilities of electrostatic actuators based on DLZ actuation systems for multi-modal compliant actuation, with potential uses in manipulation and wider robotic applications requiring torsional and axial force.