Capacitive Humidity Sensor With Enhanced Sensitivity Based on Graphene Oxide/Lignosulfonate With Laser-Induced Graphene Electrodes for Noncontact Detection

High-performance graphene-based humidity sensors have attracted significant attention in noncontact 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 article, a capacitive humidity sensor with enhanced sensitivity based on graphene oxide (GO)/lignosulfonate (LS) with laser-induced graphene (LIG) electrodes is proposed using the 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 LS is introduced into GO 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 noncontact human-interface interaction. This work can provide a strategy for designing and fabricating high-performance graphene-based humidity sensors for noncontact monitoring applications.