Dual-response behavior of chitosan humidity sensors via tailored electrode structures

Abstract

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.