Electrochemical actuation in chitosan/polyaniline microfibers for artificial muscles fabricated using an in situ polymerization

We have fabricated a new type of electroactuating biopolymer hydrogel/polyaniline microfiber by wet spinning a chitosan solution, followed by the in situ chemical polymerization of aniline. This novel biomaterial showed an enhanced chemical and electrochemical actuation in response to pH and an electrical stimulus. The fibers showed a reasonable electrical conductivity of 2.856 × 10−2 S/cm at room temperature. The strain ratio and response time during electrochemical actuation were highly dependent on the pH of the electrolyte. An isotonic strain of 0.39% during electrochemical actuation in an aqueous HCl solution at pH = 0, along with a strain of 6.73% corresponding to pH actuation was realized in the microfibers. The higher strain ratio at lower pH values is probably due to a faster diffusion rate. Although the electrochemical actuation was due to the polyaniline, the actuation mechanism was different from that in pure polyaniline. EDX analysis showed the presence of polyaniline inside the fibers, which gradually decreased moving towards the center of the fiber. SEM images of the fibers showed an agglomerated granular morphology of polyaniline particles coated on the surface of the chitosan fibers. The electrochemical properties of the fibers were due to polyaniline, as evidenced by cyclic voltammogram.