Lithium chloride-enhanced laser-induced graphene for high-performance capacitive humidity sensing

Flexible capacitive humidity sensors frequently suffer from active material leaching, weak interfacial adhesion, and complex electrode fabrication processes. To address these challenges, a lithium chloride-enhanced laser-induced graphene (LiCl/LIG) composite electrode on a polyimide (PI) substrate is obtained through a one-step, in-situ laser direct writing approach. The synthesized three-dimensional (3D) interconnected porous LIG framework provides abundant anchoring sites that spatially confine the highly hygroscopic LiCl. This architecture effectively mitigates deliquescence-driven leaching while ensuring a highly conductive signal transmission network. Consequently, the optimized sensor exhibits an ultrahigh sensitivity of 35,373.8 % (Δ C / C 0 ) across a broad working range (11–97 % RH). The device also demonstrates rapid response and recovery times (76 s and 110 s, respectively), alongside low hysteresis (5.87 %). The practical utility of the sensor is validated through high-fidelity continuous respiratory monitoring and non-contact spatial sensing applications. Furthermore, the sensor is seamlessly integrated into a portable, fully wireless smart diaper monitoring system capable of real-time moisture alerts, demonstrating substantial promise for scalable wearable electronics and intelligent Internet of Things (IoT) healthcare systems. Download: Download high-res image (430KB) Download: Download full-size image