To date, water-based ionic polymer metal composite (IPMC) is just regarded as a kind of electroactive material, whereas humidity is traditionally regarded as a disadvantageous factor, the change of which negatively influences the performance of the IPMC. However, the deformation of the IPMC is greatly sensitive to ambient humidity, and can be enhanced dramatically by changing the humidity. In this study, a novel actuation mode is proposed to control the deformation behavior of IPMC by employing moisture as an independent or collaborative incentive source together with the electric field. The deformation is continuously recorded under electric field and electric field-moisture coupling stimulus. These results are consistent with the view that the bending properties of the IPMC are a result of the balance of osmotic pressure and electrostatic stress in the membrane, which is greatly dependent on the change of humidity. Therefore, development of the coupling-drive mode is of great significance for the guidance of material design and application for the IPMC.
In this paper, we developed a new kind of ionic polymer metal composite (IPMC) actuator by doping sulfonated carbon nanotube (SCNT) into Nafion matrix to overcome some major drawbacks, such as low output force and short air-operation time, which restrict applications of conventional Nafion IPMC actuators. Firstly, SCNT was synthesized by coupled reaction of multi-walled carbon nanotubes and azo compounds and then doped into Nafion matrix by casting method. Subsequently, several key parameters of the SCNT-reinforced Nation matrix, water uptake ratio and equivalent stiffness, were revealed and the inner morphology of the membranes were observed by scanning electron microscopy. Finally, the effects of the SCNT on the electromechanical properties of IPMC actuators, especially the actuating performance, were evaluated experimentally and analyzed systematically. The results showed that SCNT was evenly dispersed in Nafion matrix and a small amount of SCNT could improve the performance of IPMC actuators significantly.