Experimental study of single-particle trapping mechanisms into microcavities using microfluidics

Single-particle trapping mechanisms into microcavities are still puzzling for size-based particle/cell sorting in microfluidics. Aiming to verify the prediction of particle-wall collision trapping mechanism, we explore the effects of the microcavity trailing wall on the single-particle trapping behaviors for various microcavity aspect ratios (lambda = 0.5-5) and inlet Reynolds numbers (Re = 5-400), uncovering three new trapping phenomena, namely, contact trapping, collision trapping, and rapid trapping. We characterize the particle velocity variation during the trapping process. We also investigate the separatrix topology (streamlines between the microvortex and microchannel flow) and map the different particle trapping phenomena. The particle trapping results from the combined effects of the microcavity trailing wall, the separatrix topology, and the particle dynamics. The results provide new insight into the fundamental understanding of particle trapping mechanisms and could guide the applications of microcavity-based microfluidics. Published under license by AIP Publishing