Preparation and sensing performance of thin ionic polymer-metal composites based on drop casting and electroless plating

Ionic polymer-metal composites (IPMC) have emerged as an ideal material for artificial skin applications due to their exceptional flexibility and skin-mimetic ion transport properties. However, conventional IPMC fabricated from commercial Nafion membranes are typically limited to a minimum thickness of 50 μm, which significantly restricts their compatibility with human skin. In this study, we developed a novel fabrication process for thin IPMC with thickness of less than 50 μm. We successfully cast Nafion films with thicknesses of 30 μm, 40 μm, 50 μm, and 60 μm by using the glass-slide drip-casting technique. Then Pd-Au composite electrodes were deposited on their surfaces by electroless plating (immersion reduction, IR) and electroplating. We analyzed and evaluated the electrochemical performance and bending sensing performance of IPMC with different thicknesses. The specific capacitance of the IPMC with a thickness of 60 μm was 3 times higher than that of the sample with a thickness of 30 μm, and the sensing performance was 4.25 times higher. Compared with the IPMC prepared from a commercial Nafion film (50 μm) of the same thickness (bending output voltage of 0.4 mV), the IPMC prepared by this process showed superior sensing performance (bending output voltage of 0.8 mV). After 1000 bending cycles, the signal attenuation rate remained below 5%. This work provides important technical support for the research and development of ultra-thin flexible sensors.