Microwave Humidity Sensor Based on PDMS Integrated CSRR Structure

Le résumé fourni par la source

Relative humidity (RH) measurements remain a significant challenge in food processing, healthcare, agriculture and various industrial applications. Commercially available ceramic-based humidity sensors require periodic “heat cleaning” to restore their sensing properties. This limits their usage for long-term and continuous monitoring applications. These limitations have driven the search for alternative sensing technologies. Microwave sensors have emerged as promising candidates owing to their ability to provide label-free, real-time monitoring, support wireless and passive operation, and allow easy miniaturization for integration into compact and flexible devices. In this work, a microwave humidity sensor based on a coplanar waveguide (CPW) excited complementary split-ring resonator (CSRR) is proposed, incorporating a hydrophobic polydimethylsiloxane (PDMS) layer coated on the optimized sensing region. The PDMS is applied via drop casting process, forming a uniform dielectric-sensitive interface that effectively interacts with moisture while maintaining stable performance under prolonged humid conditions. The proposed sensor exhibits a total resonant frequency shift of${2 4\ \text{MHz}}$and over${4\ \text{dB}}$change in the transmission coefficient across the 35% to 90% RH range, demonstrating strong sensitivity and consistent performance with minimal degradation. Its simple fabrication and compatibility with planar RF platforms makes it well-suited for miniaturized, passive, and reusable humidity sensing in real-world applications.

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