Electrically Zipping Bending Actuators for Prosthetic Fingers

State-of-the-art prosthetics use traditional ‘muscle-tendon’ systems to flex and extend fingers. The main consumer complaint is the weight of a prosthetic, aggravated by this complicated mechanism. This letter introduces an electrically zipping bending actuator (EZBA), a soft actuator that fuses structure and function into one component, reducing the weight of a single bending actuator to 2.5 g. These actuators use the dielectrophoretic liquid zipping (DLZ) actuation concept, employing an amplified electrostatic force to attract two thin insulated electrodes. Holding the bottom strip in place and moving the tip of the top strip backwards creates a buckle, a crucial part of creating a bending movement using electrostatic attraction. During actuation, the buckle decreases in size and pushes the top end of the EZBA downwards and bends the whole structure. To evaluate the actuator's performance, tip bending and generated force were measured and compared to those achieved by a human finger. The actuator bent to 89.6° (45.8 mm) and achieved a grip force of 177 mN.