Effect of ruthenium on superior performance of cellulose nanofibers/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/ruthenium oxide/ionic liquid actuators

Abstract

This study proposes novel actuators based on cellulose nanofibre/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/hydrous ruthenium oxide/ionic liquid (CNF/PEDOT:PSS/RuO2/IL) electrodes and the poly(vinylidene fluoride-co-hexafluoropropylene)/IL (PVdF(HFP)/IL) electrolyte, and investigates the effect of hydrous ruthenium oxide on the electrochemical and electromechanical properties of the proposed actuators. The proposed system contains an electrochemical capacitor electrode, which acts as both a faradaic capacitor (FC) and a small electrostatic double layer capacitor (EDLC). This hybrid capacitor is based on the FC (RuO2) mechanism, and a base polymer (PEDOT:PSS) and CNF skeleton replace carbon nanotubes (CNTs). Therefore, this device functions differently from traditional CNT/PVdF(HFP))/IL electrode actuators, which are only used as EDLC units, and CNF/PEDOT:PSS/IL (without RuO2) actuators, where PEDOT:PSS plays the role of both FC and base polymer. Devices built using the proposed actuators exhibit higher strains and greater maximum generated stresses than those exhibited by devices based on CNF/PEDOT:PSS/IL (i.e. without RuO2). Surprisingly, the synergism obtained by combining RuO2 and PEDOT:PSS is considerably greater than the enhancement achieved using PEDOT:PSS. The frequency dependences of the displacement responses of the CNF/PEDOT:PSS/RuO2/IL electrode actuators were then measured and successfully simulated using a double layered charging kinetic model. The developed films are novel, robust, and flexible, and they exhibit potential for use as actuator materials.