A path toward transferable PEDOT:PSS-based capacitive sensors: Electrical modeling and fabrication

This study presents the development and characterization of a novel transferable capacitive sensor based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the primary electrode material. The electrodes were fabricated using an in-situ deposition technique that leverages the self-adhesive, flexible, and highly conductive properties of PEDOT:PSS to enable direct and stable contact with diverse surfaces for continuous, non-invasive hydration measurement. To evaluate their performance, PEDOT:PSS-based sensors were systematically compared with alternative electrode materials—including graphite, silver, gold, and indium tin oxide (ITO)—under controlled humidity conditions. A key innovation in this work is the integration of an ultra-low-cost impedance measurement system, enabling scalable and cost-effective capacitance-based hydration sensing. The study explores sensor fabrication, material characterization, and equivalent circuit modeling, quantifying the contributions of interfacial capacitance and dielectric properties. The results show that PEDOT:PSS electrodes exhibit enhanced hydration sensitivity at the electrode-dielectric interface, confirming that hydration-driven charge transport mechanisms dominate its capacitive response. This unique property allows PEDOT:PSS to detect subtle hydration fluctuations more effectively than conventional electrode materials, making it particularly well-suited for real-time monitoring in wearable electronics, biomedical diagnostics, and environmental sensing. Although physiological validation remains an essential next step, these findings establish a foundation for integrating PEDOT:PSS-based capacitive sensors into bioelectronics, flexible sensing platforms, and environmental monitoring technologies, facilitating the development of cost-effective, non-invasive hydration sensors across multiple fields. • Transferable PEDOT:PSS-based capacitive sensors with self-adhesive properties for real-time plant hydration monitoring. • Comparative study of electrode materials (graphite, silver, gold, ITO, and PEDOT:PSS) to assess hydration sensitivity and stability. • Integration of a low-cost impedance measurement system for scalable capacitance-based sensing applications. • Equivalent circuit modeling approach quantifying interfacial capacitance and dielectric contributions in hydration sensing.