Continuous-Flow Acoustophoretic Microparticle Sedimentation in a Triangular Glass Capillary: A Systematic Parametric Investigation

Ultrasound-enhanced sedimentation offers a robust strategy for microparticle separation in microfluidics. Triangular cross-sectional channels have recently emerged as a promising architecture because the acoustic radiation force and acoustic streaming-induced drag act synergistically toward the channel base—a force-field configuration unattainable in conventional rectangular or circular channels. However, quantitative relationships between operational parameters and continuous-flow sedimentation remain unexplored. Here, we systematically investigate how five parameters—volumetric flow rate, number of active transducers, active transducer length, driving voltage, and particle diameter—affect sedimentation efficiency in a triangular glass capillary. The number of active transducers is the most influential: dual-transducer operation sustains an outlet sedimentation efficiency—defined as the fractional particle removal relative to the inlet concentration—of ~77% sedimentation at 30 μL/min versus <30% for a single transducer. Flow rate shows a threshold near 27 μL/min for the baseline configuration, and increasing transducer length from 10 to 40 mm raises the measured maximum allowable flow rate from 15 to ~50 μL/min. A minimum of 19 Vpp is required for ≥80% efficiency. Ultrasound provides the greatest benefit for 5 μm particles (from <40% by gravity to >90%), while 20 μm particles gain less. A normalized sensitivity analysis offers design guidance for acoustofluidic sedimentation platforms. These findings establish quantitative design rules and confirm the feasibility of triangular-channel architectures.