Buoyancy-driven microfluidic for concentration and classification of heterogeneous microplastics particles

Rising concerns about microplastic contamination in freshwater systems have highlighted the need for efficient, scalable, and high-throughput sampling technologies. Although microfluidic platforms have shown promise for the detection, removal, and classification of microplastics, their practical implementation has been limited by low throughput. This study presents a gravity-driven, high-throughput microfluidic device designed for continuous concentration and density-based classification of microplastic particles. The system operates at moderate Reynolds numbers and accommodates a broad particle size range (4–200 μm) and plastic densities from 910 up to 1380 kg/m 3 . The device functions both as a density-based particle classifier and as a pretreatment module for sample concentration. Performance was evaluated using controlled particle suspensions and river water samples. The device successfully separated particles with density differences as small as 0.03 g/cm 3 , enabling discrimination between plastics with closely similar material properties. When configured as a concentrator, the system demonstrated size-independent separation performance, achieving separation purities of 94–100% at throughputs up to 25 mL/min in river water samples. The gravity-driven design enabled continuous operation without external pumping complexity while maintaining high classification efficiency. The proposed microfluidic platform overcomes conventional throughput limitations and enables rapid, high-purity density based separation of microplastics across a wide size and density spectrum. Its dual functionality as both a classifier and concentrator enhances downstream analytical workflows and supports recycling applications. Environmentally, this technology offers a scalable solution for improved sampling and quantification of microplastics, contributing toward more rapid, standardized, and accurate environmental monitoring.