Development of a reusable direct current electrophoretic microfluidic platform for qualitative microplastic assessment in aqueous environments

Microplastic pollution in aquatic environments requires monitoring technologies that are rapid, portable, and capable of operating outside centralized laboratory settings. This study presents the design, fabrication, and experimental evaluation of a direct-current electrophoretic microfluidic device integrated with miniaturized optical visualization for qualitative assessment of microplastics in water samples. Numerical simulations were performed to optimize electrode configuration, interelectrode spacing, and applied voltage, enabling prediction of electric field distribution and particle force response across a range of microplastic sizes and polymer types. A reusable polydimethylsiloxane-based microfluidic chip was fabricated using an embedded scaffold removal (ESCARGOT) method, allowing low-cost and accessible manufacturing without cleanroom infrastructure. Experimental testing was conducted using expanded polystyrene, polyethylene terephthalate, and nylon microplastics subjected to controlled acidic and basic degradation to induce surface charge modification. Results demonstrate that microplastic electrophoretic behavior is strongly dependent on particle size, polymer density, surface charge, and solution pH. While electric field attenuation through the polymer substrate limited on-chip electrophoretic trapping under single-pass flow conditions, exposed-electrode experiments confirmed voltage-dependent particle adhesion, particularly for base-treated microplastics. These findings validate the feasibility of electrophoresis as a manipulation mechanism for microplastics and identify key material and design constraints for future optimization. The proposed platform offers a low-complexity, reusable, and field-deployable approach for preliminary microplastic monitoring, bridging the gap between laboratory analysis and in situ environmental assessment.