Soft actuators based on Ionic Polymer-Metal Composites (IPMCs) are of considerable interest for applications in biomedical devices and robotics. In this work, thin commercial and thick laboratory-prepared Nafion membranes were made into model IPMC actuator devices by incorporation of Pt electrode layers. In extensive electromechanical tests the maximum average tip displacement and maximum force generated were recorded. The effect of amplitude and frequency of the applied voltage on both displacement and force was examined as were the effects of the origin of the Nafion membrane, the Pt loading, the structure of the electrode and the presence or absence of an Au overlayer. The cast samples generated much smaller displacements but much larger forces than the commercial Nafion samples. For all samples, displacement and force increased with increasing applied voltage, with increased number of Pt plating cycles and when an Au overlayer was present but decreased with increasing applied voltage frequency. Waveform analysis of applied voltage, current and force was performed by considering the capacitive nature of the IPMC actuators.