Toward a new generation of electrically controllable hygromorphic soft actuators

A double-layered, anisotropic humidity-driven actuator based on an ultrathin active layer of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and a passive layer composed of poly(dimethylsiloxane) (PDMS) was reported, with intrinsic sensing capability, and able to be controlled both by joule effect or directly by environmental humidity variations. After each deposition step, the samples were placed on a hot plate in ambient air for 5 min at 170°C and air plasma treated at 5 W for 10s. Finally, the samples were subjected to a thermal treatment. A direct write CO₂ laser with tunable laser power, speed, and resolution was then used to cut and pattern the samples, making it feasible to fabricate a wide range of soft actuator designs and configurations. To provide the electrical input voltage to the material, gold electrodes were added to the surfaces of the actuators. Thickness measurements were performed using a P-6 stylus profilometer. The adopted processing strategy, which consists of a few steps of spin coating, direct laser cutting, and patterning, is particularly appealing because it enables rapid and simple fabrication to test soft actuators with more complex designs.