Dual-Resonant Metasurface Sensor for Solid-Liquid Medium Detection

This paper proposes a dual resonance metasurface sensor for accurate detection of solid and liquid media. The sensor uses a complementary split-ring resonator (CSRR) coupled with a vertical metal strip on the back. The electromagnetic field confinement effect of this structure enhances the electric field density, thus improving the sensor's sensitivity. Based on equivalent circuit models and full-wave electromagnetic simulations, the dual-resonance unit of the sensor has been optimized. Results indicate that the sensor generates resonance peaks at 6.06 GHz and 7.55 GHz. Simulations show that variations in the dielectric constant of liquids and solids can cause frequency shifts of up to 3.94 GHz and 2.74 GHz in the two frequency bands, respectively. A multiple regression model was employed to fit the data, achieving a goodness of fit of R²>0.996. In experimental verification, the sensor demonstrated a maximum detection sensitivity of 182.8 MHz/ε' for liquids and 454 MHz/ε' for solids, outperforming similar sensors. The dual-frequency resonance provides differential frequency-shift information, which effectively improves the detection accuracy. The maximum normalized sensitivity of the sensor was found to be 6.5% and 2.4% for solid and liquid media respectively. The sensor is fabricated on a low-cost FR4 substrate and offers high sensitivity and adaptability to multiple media types, providing an efficient solution for applications in chemical analysis, environmental monitoring, and other relevant fields.