MICROFLUIDIC MICROPLASTIC SEPARATION: USING FLUID-CARRYING MICROCHIPS TO FILTER AND SORT MICROPLASTIC PARTICLES

As microplastics continue to contaminate our natural environment, it is becoming increasingly important to understand not only how microplastics affect the people, animals, and plants that ingest and interact with them, but also where the microplastics originate. If we can successfully categorize microplastics, understanding where they came from, then we can target our sustainability efforts for maximum positive effect. Current techniques can accurately sift and sort microplastics of sizes greater than 48µm in dimension. Anything below that range is particularly difficult to process as separation methods fail to keep important details about the plastics’ past intact. This problem is particularly prevalent in cohesive and organic-rich sediment samples like tidal marsh soils.

In this paper we present a separation method based on an intertial, spiral separator microfluidic chip. The forced flow in the chip is characterized by a strong swirl motion which exerts centripetal forces within the fluid. The centripetal forces can be used to separate micro-sized particles based on their mass and size. This is potentially achieved by causing the particles to re-distribute along the spanwise direction of the chip. Using this process, we hope to sort and categorize microplastics while preserving their morphology.

Current work has demonstrated partial separation of microplastic spheres, but full separation has not yet been achieved. Theory suggests that larger particles should be pushed to the inner wall of the chip, but our experiments have yielded smaller particles being pushed to the inner wall. This raises the question of what other forces are at play.