SRR-Based Disposable Microwave-Microfluidic Sensor for Assessing Liquid Carrier Influence on Microplastic Detection

Efficient monitoring of Microplastics (MPs) in water systems, particularly in agricultural runoff and irrigation sources, is crucial for assessing their impact on soil and crop health. This work proposed a double split-ring resonator (SRR) based microwave-microfluidic sensor that minimizes the effects of liquid carrier composition on MP detection in aqueous samples. To simulate agricultural conditions, deionized water, tap water, and solutions of urea, sodium chloride, potassium nitrate, and sodium nitrate were tested as liquid carriers. The sensor was validated using polyethylene particles in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{2 5 0 - 3 0 0} \boldsymbol{\mu}$</tex> m size range. Average frequency shifts of 374 kHz and 691 kHz were observed for each SRR, highlighting their high sensitivity and consistent performance across varying liquid carriers. The results demonstrated that the liquid carrier composition significantly influences sensor efficiency, which is a necessary step in adapting the sensor for real-world environmental conditions, establishing a foundation for scalable technologies to support sustainable agriculture and protect water quality.