Abstract:Microfluidics provides a new platform for the manipulation of particles and cells. The particle sorting method based on particle inertial migration and vortex trapping in microcavities has become an important microfluidic particle manipulation technique. Currently, the number of captured particles accommodated by the microcavity is not high, which restricts the sorting efficiency of this method. To improve the holding capacity, different round microcavities were designed, and their holding characteristics for sorted particles were investigated by using high-speed microimaging technology and numerical simulation. The results show that under the same inlet Reynolds number (Re=37~555), the number of captured particles in a round microcavity with a bottom chamber can be enhanced by 45% compared with that in an ordinary round microcavity. At Re=444, the holding capacity in a round cavity with a diameter of 500 μm increases by 54.7% compared to that with a diameter of 600 μm. The reason is that the particle motion track in the former cavity is more consistent with the streamlines, and the particle trajectory area and cavity area ratio researches 97%. The maximum concentration of 20-μm particles collected from the side channel is 126.7 times higher than that of the initial suspension. The results could provide useful guidance for the microcavity design and improvement of particle sorting performance.