Wireless dual stimuli actuation of dye sensitized conducting polymer hybrids

Abstract : Actuators controlled by external stimuli have received a lot of attention in recent years. Herein we report a polymer based dual stimuli actuator, triggered by light and an electric field. This allows a better control of actuation, enlarging the field of potential applications, like e.g. in the frame of soft robotics. The actuator is composed of polypyrrole (PPy) and TiO2 modified with methylene blue (MB). In aqueous solution, the resulting freestanding hybrid film shows reversible actuation due to the synergy of light and an applied electric field. Illumination with light produces electron-hole pairs in the TiO2 layer, which are shuttled to the opposite ends of the actuator by the potential gradient present in solution. This results in electrochemical oxidation and reduction reactions at the two extremities and consequently in site selective swelling of the polymer, which finally leads to a controlled motion of the actuator, following the principles of logic gate operations. Such synergistically induced switching allows developing original actuation schemes for performing complex mechanical tasks triggered by more than one stimulus.