Inertial microfluidics is able to focus and separate particles in microchannels based on the characteristic geometry and intrinsic hydrodynamic effect. Yet, the vertical positions of suspended particles in the microchannel cannot be manipulated in real time. In this study, we utilize the boundary slip effect to regulate the parabolic velocity distribution of fluid in the microchannel and present a scheme to actively control the vertical positions of particles in inertial microfluidics. The flow field of a microchannel with a unilateral slip boundary is equivalent to that of the microchannel widened by the relevant slip length, and the particle equilibrium positions in the two microchannels are consistent consequently. Then, we simulate the lateral migrations of three kinds of typical particles, namely, circular, elliptical, and rectangular in the microchannel. Unlike the smooth trajectories of circular particles, the motions of the elliptical and rectangular particles are accompanied by regular fluctuations and nonuniform rotations due to their noncircular geometries. The results demonstrate that the unilateral slip boundary can effectively manipulate the vertical equilibrium positions of particles. The present scheme can improve the accuracy and flexibility of particulate focusing, separating, and transport in inertial microfluidics.

• Received 20 January 2022
• Accepted 31 May 2022

DOI:https://doi.org/10.1103/PhysRevFluids.7.064201