Preparation and performance of IPMC actuators with electrospun Nafion®–MWNT composite electrodes

A new ionic polymer actuator was prepared with Nafion®-117 membrane and electrodes made of an electrospun Nafion®/multiwalled carbon nanotube (MWNT) web. The surfaces of composite electrodes were ion-beam coated with gold layers of 2–3 μm thickness to reduce the surface resistance. The composite electrodes offer several advantages over conventional platinum electrodes prepared via electroless plating process, i.e. flexibility, simple processability in large scales, and batch-to-batch reproducibility. The new ionic polymer–metal composite (IPMC) actuators showed a rapid and large bending motion. Under an applied potential of 3 V dc, the maximum horizontal displacement (δmax) measured at the tip of IPMC strip (cantilever length: 20 mm) was 16.7 mm, the tip velocity in the initial linear region was 10.5 mm/s, 88% of the δmax was reached within initial 5 s, and the generated strain% was 0.79 (13.6 mm, 7.2 mm/s, 85%, and 0.88, respectively for a conventional Nafion®–IPMC made via the electroless plating of platinum). It was noted that the energy efficiency of strain was over 10 times higher than that of the conventional Nafion®–IPMC. And the crack formation of metal electrode after repeated bending deformation significantly reduced with the introduction of relatively flexible electrode assembly into the IPMC architecture. The remarkable improvements in its performance were considered to be due to the efficient quantum chemical and double-layer electrostatic effects in a charge injection model, induced by the good dispersion of MWNTs through a typical electrospinning technique.