A Cost-Effective and High-Sensitivity Optofluidic Refractive Index Sensor for Rapid Edible Oil Analysis

Edible oil plays an irreplaceable role in the diet worldwide. It not only grants unique flavors to the food but also provides the necessary nutrition we need for daily life. Therefore, the quality of edible oil directly affects our health conditions, and public health issues caused by unqualified edible oil occur every year, especially in low-income populations. Unfortunately, currently available edible oil detection methods usually involve bulky equipment and various reagents which are cost intensive and not friendly to undeveloped areas. In this study, we design and fabricate a disposable sensor for edible oil detection with high sensitivity by measuring the refractive index (RI) of the edible oil using an arched optofluidic waveguide. The experimental results show that our sensor can measure the RI of the edible oil with a high sensitivity of 16.175 mW/RIU and a low-noise-equivalent detection limit (NEDL) of $4.099\times 10^{-{5}}$ RIU simultaneously in a dynamic range from 1.45839 to 1.47399 RIU. In addition, our miniaturized sensor can rapidly detect a sample within only 30 s, providing a highly efficient and convenient solution for edible oil analysis in various settings. The remarkable RI sensing capability enables the sensor to distinguish different types of commercial edible oil. Moreover, our sensor can accurately monitor the RI change of the edible oil as the frying time increases, which is potentially employed for nutrition/toxicological evaluation. We believe our sensor that can provide a promising solution for cost-effective and high-sensitivity edible oil detection in underdeveloped areas and hence contribute to human health.