A Dual-Mode X-Cut LiNbO3 Saw Sensor for Humidity Sensing with Inherent Temperature Decoupling

This study presents a dual-mode surface acoustic wave (SAW) sensor based on X-cut lithium niobate, utilizing Rayleigh and shear horizontal modes for simultaneous humidity and temperature sensing with inherent decoupling. The one-port SAW sensor fabricated via photolithography was functionalized for humidity sensing by coating graphene oxide using an electrospray deposition method. The SAW sensor exhibited excellent sensitivity, measuring$91.16 \text{ppm} /{ }^{\circ} \mathrm{C}$for temperature and 108.05$\text{ppm} / \% \text{RH}$for humidity. By leveraging both resonant modes, the sensor accurately decoupled temperature and humidity responses while achieving sensitive and stable performance under both low and high humidity conditions.