Engraved Split-Ring Resonators as Potential Microwave Sensors for Olive Oil Quality Control

In this study, microwave complementary split-ring resonators are explored regarding their sensing capability against olive oil adulteration. In particular, millimeter-scale complementary split-ring resonators were developed employing the computer numerical control method, in combination with a home-built mechanical engraver. Their electromagnetic behavior was comprehensively studied, both experimentally and theoretically, in the frequency range of 2-9 GHz. Furthermore, their electromagnetic response was investigated in the presence of different types of edible oils, such as virgin olive oil, corn oil, and soybean oil. Both experimental results and theoretical simulations clearly reveal the distinct response of the fabricated complementary resonators to different oil types. Even more, they exhibit a significant response in oil mixtures, enabling the detection of possible adulteration in olive oil. Consequently, it becomes evident that mechanically engraved microwave complementary split-ring resonators can be efficiently realized as potential sensors for olive oil quality control.