Development of Solid-in-Hollow Electrochemical Linear Actuators Using Highly Conductive Polyaniline

In this paper, we report the use of highly electrically conductive (400−1000 S/cm) polyaniline fibers for the development of electrochemical linear actuators. The high conductivity of the fibers ensures well-defined electroactivity and actuation without a metal backing. In propylene carbonate (PC), the electrochemical and actuation behavior of the fibers was influenced by the dopants' solubility and size: solubility in the electrolyte ensured easy expulsion from the polymer, thus facilitating ion transport and resulting in high electroactivity and strain in the fibers. Actuation of fibers was also affected by electrolyte anions. Small anions led to anion-exchange dominated actuation, and large anions led to cation-exchange dominated actuation. Electrochemical linear actuators with a unique solid-in-hollow configuration were developed using a polyaniline solid fiber in a polyaniline hollow fiber with a gel electrolyte. These actuators were simple to construct and allowed two-electrode operation. Isotonic strains of 0.9% and isometric stresses of 0.9 MPa were realized.