As an excellent transducer, ionic polymer-metal composites (IPMCs) can act as both an actuator and a sensor. During its sensing process, many factors, such as the water content, the cation type, the surface electrode, and the dimensions of the IPMC sample, have a considerable impact on the IPMC sensing performance. In this paper, the effect of dimensions focused on the Pd-Au typed IPMC samples with various thicknesses, widths, and lengths that were fabricated and their deformation sensing performances were tested and estimated using a self-made electromechanical sensing platform. In our experiments, we employed a two-sensing mode (both current and voltage) to record the signals generated by the IPMC bending. By comparison, it was found that the response trend was closer to the applied deformation curve using the voltage-sensing mode. The following conclusions were obtained. As the thickness increased, IPMC exhibited a better deformation-sensing performance. The thickness of the sample changed from 50 μm to 500 μm and corresponded to a voltage response signal from 0.3 to 1.6 mV. On the contrary, as the length increased, the sensing performance of IPMC decreased when subjected to equal bending. The width displayed a weaker effect on the sensing response. In order to obtain a stronger sensing response, a thickness increase, together with a length reduction, of the IPMC sample is a feasible way. Also, a simplified static model was proposed to successfully explain the sensing properties of IPMC with various sizes.

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.