Sensing characteristics of a conducting polymer/hydrogel hybrid microfiber artificial muscle

Linear artificial muscles of hydrogel microfibers coated with a conducting polymer can act while working, as a sensor of driving current, electrolyte concentration and temperature. Hybrid conducting polymer/hydrogel microfibers were fabricated from a chitosan solution through wet spinning technique followed by in situ chemical polymerization of pyrrole in aqueous medium using bis(triflouro methane sulfonyl) imide as dopant. The hybrid microfiber was characterized by FTIR, electrical conductivity measurement, scanning electron microscopy, dynamic mechanical analysis, cyclic voltammetry and chronopotentiometry. The fiber showed an electrical conductivity of 3.1 × 10−1 S cm−1. The electro activity was imparted by polypyrrole. An electrochemical linear actuation strain of 0.54% was achieved in aqueous electrolyte. The electrochemical measurements were performed as a function of applied current, temperature and concentration for a constant charge in 1 M NaCl. The chronopotentiometric responses during the oxidation/reduction processes and the resulting linear fit of consumed electrical energy during reaction of the hybrid microfiber for different anodic/cathodic currents and at different temperatures showed that it is a sensor of applied current and temperature, respectively. A logarithmic dependence of the consumed electrical energy with concentration of the electrolyte during reaction suggested that it can act as a concentration sensor.