Dual-Response Behavior of Chitosan Humidity Sensors via Tailored Electrode Structures

Accurate humidity measurement is critical in environmental monitoring, industrial process control, medical diagnostics, and related fields. The use of humidity-sensitive materials exhibiting dual capacitance/resistance response characteristics offers a promising strategy to enhance sensor applicability. In this study, a chitosan humidity sensor was developed to systematically investigate its dual-response behavior under varying humidity conditions (6%–92%RH). Sensors with different interdigitated electrode configurations were fabricated and characterized at 1 kHz to evaluate their humidity sensing performance. Experimental results demonstrate outstanding sensor performance, including high response (5382.29% in capacitance and 99.99% in resistance) and rapid response/recovery times (within 10 s and 30 s, respectively). Among the configurations tested, the interdigitated electrodes design exhibits the most pronounced capacitance response, accompanied by a notable resistance response and the fastest response/recovery times, establishing it as the optimal electrode structure. The dual-response mechanism was elucidated using a water adsorption model, revealing distinct capacitance and resistance behaviors, while different electrode configurations modulate ion transport pathways and electric field distribution, accounting for the observed performance differences. Non-contact sensing tests further validate the practical potential of the dual-response characteristics. These findings provide valuable insights for optimizing the design and expanding the applicability of advanced humidity sensors.