Numerical simulation of particle migration in different contraction–expansion ratio microchannels

Abstract

Inertial microfluidic device has been widely used for particle/cell manipulation in recent years, due to the attractive advantages of high throughput, low cost and simple operating. As a typical inertial microfluidic microchannel pattern, the contraction–expansion microchannel is usually applied for particle focusing or separation because of the ability to be easily parallelized. However, the mechanism of particle focusing in this channel is still vague and the effects of microchannel dimension have not been considered in the former experimental researches. This paper reports the particle migration characters in microfluidic channels with contraction–expansion ratio γ = 1.0 and γ = 2.0 through numerical simulation and corresponding validation experiments. Based on lattice-Boltzmann method (LBM)–immersed boundary method (IBM) model, which numerically describes the particle behavior in the microfluid, we study the particle-focusing mechanics in contraction–expansion microchannels further with the particle trajectory and rotation data which are not easily observed in experiments. With the simulation results, it can be found that contraction–expansion ratio can obviously influence the particles on their focusing patterns. A large γ continuous contraction–expansion microchannel needs higher flow rate to keep different-sized particles separated and has better focusing performance. The secondary flow in the cross section plays an important role to focus different size particles at different equilibrium positions. Research results of these sheathless and easily paralleled contraction–expansion microchannels can provide helpful insight for particle/cell detection chip design in the future.