Capacitive humidity sensor with enhanced sensitivity based on graphene oxide/lignosulfonate with laser-induced graphene electrodes for non-contact detection

High-performance graphene-based humidity sensors have attracted significant attention in non-contact detection and human-interface interaction. Nevertheless, fabricating high-performance graphene-based humidity sensors using low-cost and environmentally friendly approaches remains a challenge. In this paper, a capacitive humidity sensor with enhanced sensitivity based on graphene oxide/lignosulfonate with laser-induced graphene electrodes is proposed using laser direct writing technology and the drop-coating method. NOMEX polyimide composite paper is employed to prepare interdigitated electrodes through laser direct writing technology. Renewable lignosulfonate is introduced into graphene oxide as a humidity-sensitive layer to enhance the humidity-sensing performance of the sensors. The sensitivity can be greatly improved to 58057 pF/% RH under the optimized parameters. Meanwhile, the graphene-based humidity sensor features low hysteresis, excellent repeatability, and long-term stability. Furthermore, the humidity sensor demonstrates potential application in human respiration monitoring and non-contact human-interface interaction. This work can provide a strategy for designing and fabricating high-performance graphene-based humidity sensors for non-contact monitoring applications.