Three electrochemical tools (motor-sensor-battery) with energy recovery work simultaneously in a trilayer artificial muscle

Abstract Biological evolution has developed organs able to perform different functions as sensing and tactile motors (haptic muscles). There, different tools (one motor and several sensors) work simultaneously driven by biochemical reactions. Here we present electrochemical triple-tool (actuator-sensor-battery) trilayer artificial muscles driven by reversible electrochemical reactions including two films of conducting polymers (CPs) where every CP chain acts as a multistep molecular machine. Any imposed constant current drives the reversible oxidation of one of the CP films and the simultaneous reduction of the second CP film. The symmetric change of the reaction-driven film volume variations originates the macroscopic bending movement of the polymeric motor. The bending angle follows a linear function of the consumed charge. The simultaneous reaction-driven divergent composition (polymer/ion) variation of the two films originates a change of the potential gradient between them: the muscle potential. The evolutions of: the muscle potential, the consumed electrical energy or the consumed power are a function of (sense) the mass trailed by the muscle: the muscle senses the working mechanical conditions. The increase of the muscle potential during actuation indicates the charge of a battery. Here the trilayer is studied as a battery that charges during bending, rending back up to 83% of the charge and a fraction of the electrical energy consumed to bend the muscle during de-bending. Considering such energy recovery, the efficiency of the actuators may increase up to one order of magnitude. Three tools (actuator-sensor- battery) work simultaneously in a trilayer driven by oxidation/reduction reactions of the constitutive polypyrrole films. Only two connecting wires contain, simultaneously, actuating, sensing and battery magnitudes.