Electroactive actuator based on polyurethane nanofibers coated with polypyrrole through electrochemical polymerization: a competent method for developing artificial muscles

Abstract

In the present study, the electrochemical polymerization was carried out to coat the surface of electrospun polyurethane (PU) nanofibers with conductive electroactive polypyrrole (PPy) towards production of Faradaic bending actuators. For this purpose, the surface of electrospun nanofibers was first coated with a thin layer of gold using physical vapor deposition (PVD). PPy was then coated on the surface of prepared nanofibers using different consumed electric charges ranging from 0.5 to 5 C. The produced samples were characterized with respect to surface morphology, electrical properties, electrochemical properties and finally bending actuation performance of the produced actuators. The synthesis of PPy on the surface of nanofibers by the electrochemical polymerization process as well as preservation of the fibrous and porous structure of the samples was confirmed by SEM images. In the polymerization process, the amount of PPy coating on the surface of PU nanofibers increased dramatically with increasing the consumed electric charge. The results of the electrical properties of the produced nanofibrous layers showed that the surface resistivity of the produced PU/PPy nanofibrous layer was decreased from 719.5 to 51.3 Ω/sq for samples produced with the consumed charges of 0.5 and 5.0 C, respectively. Moreover, the electroactive properties of produced actuators were evaluated by cyclic voltammetry technique in a 0.1 M aqueous electrolyte solution of LiClO4 between potentials of −0.6 to 0.8 V. The results revealed that the electroactive properties of produced actuators were improved with increasing the amount of PPy coating. The evaluation of the bending actuation performance of the actuators showed that the angular displacement of the samples produced with consumed charges of 2, 3, 4 and 5 C in a potential cycle was 48°, 153°, 190° and 225°, respectively. These actuators have the potential to be applied in the fields of medicine, robotics and smart textiles.