Detection of microplastics by microfluidic microwave sensing: An exploratory study

Detection of microplastics in water environments and consumables is essential to evaluate the abundance, sources, transport pathways, degradation, and exposure risks of these emergent contaminants. In this study, we explore the potential of detecting microplastics in aqueous samples using a microwave sensor integrated in a microfluidic platform. The principle relies on the change in permittivity of the water due to the presence of microplastics that, in turn, leads to a resonance frequency shift recorded by the microwave sensor. The method is tested using 20 and 70 µm polyethylene microspheres. Both the experimental data and the numerical simulations show consistent dependencies of the frequency shift on the size and concentration of the microspheres, as well as on temperature. However, the experimental trends in resonance frequency are not as pronounced as predicted by the numerical simulations. In addition, the limits of detection of the current microwave-microfluidic device are much higher than the typical particle abundances encountered in most freshwaters. Based on these preliminary results, we outline potential directions for the further development of microfluidic microwave sensing of microplastics in water samples. • A compact microfluidic-microwave system is developed for rapid and cost-effective microplastic (MP) detection. • The system integrates a microwave resonator and microfluidic platform for sensitive MP concentration monitoring. • Detection uses resonance shifts due to changes in water permittivity caused by MPs. • Higher temperatures improve sensitivity, as shown by testing across 10°C–30°C. • Offers a low LOD (1000k/70µm, 10000k/20µm).