Microfluidics-based electrophoretic capture and Raman analysis of micro/nanoplastics

Global concern about micro/nanoplastic contamination in aquatic ecosystems reflects the heightened awareness of its environmental impact. Micro/nanoplastics, found in diverse environments, exhibit distinctive characteristics influenced by their polymer composition, such as variations in color and density. Addressing the critical issue of micro/nanoplastic contamination requires a multifaceted approach, encompassing various techniques for detection and mitigation, including filtration, centrifugation, magnetic separation, and others. Currently, microplastics detection requires separate isolation and analysis, making the detection process cumbersome and possible cause for potential sample loss.

In this study, we use the electrophoretic force on micro/nanoplastics (≤5 μm in size) flowing in an aqueous sample inside a fluidic channel to effectively capture the particles on a substrate. A direct current (DC) voltage is applied using an asymmetric electric field on the fluidic channel to induce electrophoresis of the microplastics. The captured microplastics can be characterized in situ through Raman spectroscopy and optical microscopy, enabling concurrent analysis of particle size, shape, and type. Using the method, we demonstrate the detection of micro/nanoplastics leached from a commercial teabag.

The method shown here enables rapid and easy detection of small microplastics that are otherwise difficult to capture using conventional methods. In particular, eliminating the need for separation isolation and analysis steps is a huge advantage considering the potential loss of sample due to its low concentration.