3D structured polypyrrole/reduced graphene oxide (PPy/rGO)-based electrode ionic soft actuators with improved actuation performanceElectronic supplementary information (ESI) available: (a) The chronopotentiogram plots and (b) trend of constant potential obtained during the electropolymerization of PPy/rGO films in the fabrication of actuators (Fig. S1). See DOI: 10.1039/c8nj00936h

Here, we report a facile approach to fabricate flexible 3D structured polypyrrole/reduced graphene oxide (PPy/rGO) electrodes for Nafion-based ionic soft actuators. rGO nanosheets were homogeneously attached into the PPy framework using the electropolymerization of PPy/rGO nanocomposites on both faces of carbon nanoparticle/MWCNT (CA)-coated Nafion membranes. This improved the electron and ion transport processes, which are prerequisites for the actuation performances of ionic soft actuators. The prepared 3D PPy/rGO actuators provided a significantly larger active area, faster ion transfer ability, higher mass transfer efficiency and excellent capacitive characteristics. The surface morphology and porosity of the electrode layers were altered by changing the rGO content of the electrodes, as confirmed by SEM images and electrochemical impedance spectroscopy (EIS) measurements. The capacitive characteristics and ion exchange capacity (IEC) of the prepared actuators were considerably improved by adding up to 3 wt% rGO. This resulted in a significant improvement of the electro-mechanical energy efficiency (∼2 times) and the bending deformation (∼5 times) of the 3D PPy/rGO actuators compared to actuators prepared using a similar method containing no rGO. The presented processing strategy for fabricating metal-free soft ionic actuators provides opportunities toward developing a new class of 3D structured soft robotics for medicinal and industrial applications. We report a facile approach to fabricate 3D polypyrrole/reduced graphene oxide (PPy/rGO)-based electrodes for Nafion-based ionic soft actuators.