Fabrication of SGO/Nafion-based IPMC soft actuators with sea anemone-like Pt electrodes and enhanced actuation performance

In the current work, graphene oxide (GO) and sulfonated graphene oxide (SGO) were synthesized and composited with Nafion to increase the water uptake (WUP) and ion exchange capacity (IEC) of the cast membranes. Ionic polymer-metal composite (IPMC) soft actuators in protonated form were fabricated based on the cast pure Nafion, Nafion/GO and Nafion/SGO membranes. The effects of incorporating GO and SGO in IPMC actuators were followed using physicochemical, electrochemical and electromechanical measurements and were compared with the corresponding behavior of pure Nafion-based IPMC actuators. Morphology analysis of IPMCs showed effective incorporation of GO and SGO and clarified the dependency of Pt electrode structure on the SGO content of the Nafion membranes. The addition of SGO resulted in dramatic increases in the WUP, IEC and hydrated thickness of the Nafion membranes and also in the capacitance, ionic conduction and in the tip displacement of the IPMC actuators. The small tip displacement of pure Nafion-based actuator was enhanced by eight times by adding 1 wt% SGO. The results suggested that the dispersion of SGO throughout the continuous polymeric matrix significantly reduce water loss by increasing the obstructions within the Nafion membrane and also by formation of denser Pt grains in the electrode regions.