Development and operational characterization of an Acoustofluidic trap for microplastic separation from water systems

Microplastic pollution from domestic textile washing represents a significant and persistent environmental challenge, with conventional filtration methods suffering from clogging and limited efficiency for small particles. This study presents the development and operational characterization of a 3D-printed acoustofluidic trap using acoustic radiation forces for microplastic separation from water systems. The device employs a 2 MHz ultrasonic standing wave field within a stainless steel flow channel to capture particles at pressure nodes within the standing wave field. Computational fluid dynamics modeling guided optimization of flow distribution and particle trajectories, leading to development of a symmetrical dual-inlet architecture that achieved capture efficiencies exceeding 95% for 85 μm polystyrene microspheres at concentrations of 150 mg/L and flow rates of 150 mL/min. The system demonstrated versatility by efficiently capturing particles ranging from 32 to 85 μm spheres to 0.5 mm × 13 μm polyester microfibers, maintaining efficiency while processing 1.5 L. Operational characterization revealed temperature-dependent frequency drift as a critical factor affecting long-term stability, with performance declining after approximately 10 min of operation due to thermal-induced resonance drift and particle accumulation. These findings demonstrate acoustic trapping as a possible point-of-source technology while identifying several operational challenges requiring further development for practical implementation in domestic applications.