Experimental Control of Piezo-resistivity in Thick Film Resistors throughMaterial Characteristics and Processing Parameters

Introduction: Polymer-based thick-film resistors using PVC–graphite/nickel composites have attracted considerable attention for strain-sensing applications due to their mechanical flexibility, low fabrication cost, and tunable electrical properties. However, the relationship among filler characteristics, processing parameters, and resistance variation under mechanical strain remains unclear. This study aims to investigate the influence of graphite grain size, filler composition, and processing conditions on the strain-dependent electrical behavior of PVC–graphite/nickel thick film resistors. Methods: Thick-film resistor samples were fabricated using Polyvinyl Chloride (PVC) as the polymer matrix, with graphite and nickel fillers of varying grain sizes and proportions. The composite films were prepared through controlled processing conditions, including temperature, curing time, and film thickness. Electrical resistance measurements were performed under controlled uniaxial tensile strain to evaluate the strain–resistivity relationship and normalized resistivity variation. Results: The experimental results show that increasing graphite grain size significantly enhances the normalized resistivity variation under applied strain. The magnitude of resistivity change is influenced not only by the filler microstructure but also by processing parameters such as film thickness and dispersion uniformity. The observed behavior is attributed to straininduced displacement, separation, and reorientation of conductive graphite particles within the PVC matrix, which modifies the conductive pathways. Discussion: The findings highlight the important role of conductive network evolution in determining the piezoresistive response of polymer-based thick film resistors. By optimizing filler characteristics and fabrication parameters, the strain sensitivity of the composite films can be effectively tuned for sensing applications. Conclusion: The study demonstrates that appropriate control of material composition and processing conditions significantly enhances the strain sensitivity of PVC-graphite/nickel thick film resistors, indicating their strong potential for flexible, low-cost strain sensing in smart structures, energy systems, and industrial monitoring applications.