Scalable fabrication of ionic and capacitive laminate actuators for soft robotics

Abstract

Soft electrochemically-driven actuators based on high specific surface area electrodes and having a laminate structure similar to the electrical double-layer capacitors are attractive for future generations of biomimetic robotics. Successful incorporation of such ionic and capacitive actuators into soft robots demands highly repeatable and scalable fabrication techniques. As a novel approach in fabrication of ionic and capacitive laminates, the electroactive layers are deposited layer-by-layer around a woven fabric substrate, which is pertained as the centermost layer of the laminate. The electromechanical performance of the actuators having the textile reinforcement layer was on a par with similar actuators without the reinforcement layer; however, the reinforcement layer significantly simplifies the manufacturing process and increases repeatability of the actuators characteristics. More importantly, the reinforcement layer pertains its tensile strength, which gives new opportunities for incorporation of the soft ionic actuators directly onto fabric without compromising their excellent electromechanical performance. Fortunately, the same electroactive laminates, directly exposed to ambient air, have outstanding performance as electric double-layer capacitors for energy storage. Electromechanical characterization with a galvanostatic input was carried out on a large pool of actuators to identify the factors influencing the repeatability of their actuation. The new fabrication procedure yields electroactive laminates with outstanding uniformity in thickness and areal capacitance (standard deviations at 95% confidence interval are 9.2% and 9.4%, respectively) and with a lifetime of more than ten thousand cycles.