Reversible and Flexible Electrolytic Actuator with 3D Porous Carbon Nanotube Electrodes for Enhanced Displacement

This paper reports a reversible and flexible electrolytic actuator employing a sublimation-derived porous 3D carbon nanotube (CNT) electrode, which enhances gas generation and displacement. The 3D electrode pattern is formed via drop-casting and freeze-sublimation of CNT ink confined to hydrophilic domains patterned by selective plasma treatment. This low-temperature, ink-based process enables direct patterning and porous structuring of CNT electrodes on flexible substrates, without requiring highvacuum deposition or high-temperature annealing. The electrode formation method is scalable and enables the large-area integration of CNTs. Compared to flat CNT electrodes formed by drying, the porous structure provides an enlarged surface area, leading to a 780% increase in displacement under identical conditions. Furthermore, by driving the actuator with high-frequency (200 kHz) AC power, spontaneous combustion of nanobubbles is induced, facilitating gas recombination and enabling mechanical relaxation within seconds. This study demonstrates that electrolytic actuators-previously limited by slow reversibility or small displacement-can be applied to wearable haptic interfaces and soft robotics.