Highly Sensitive and Robust Metasurface-Inspired Microfluidic Sensor for Oil Detection

In this article, a low-cost, robust, and highly sensitive microfluidic sensor is proposed, leveraging a complementary split-ring resonator (CSRR) operating at microwave frequencies. The sensor design incorporates a U-shaped microfluidic tunnel within each unit cell structure, facilitating the identification of various liquid samples with minor dielectric constant variations through spectrum measurement. The measurement results indicate a resonant frequency shift of 1.54 GHz is achieved for a change in the dielectric constant of 1, and the capability of the microfluidic sensor in detecting several common oils is experimentally demonstrated. Moreover, a liquid constant temperature circulation system is included in this design, and the test error induced by the fluctuation of liquid temperature, which contributes to most of the measurement error, can be reduced significantly. Due to its robustness and high sensitivity, this passive metasurface-based microfluidic sensor provides promising potential for liquid sample detections with minor dielectric constant variations.