Direct Numerical Simulation of Particle Segregation and Dynamics in Inertial Microfluidics By Discrete External Boundary Force-Lattice Boltzmann Method

Abstract

In the last decade, inertial microfluidics has attracted considerable attention for particle manipulation including particle focus, concentration and separation. To illustrate the detailed underlying mechanism of the particle segregation occurring in inertial microfluidics, dynamics of a single and multiple neutrally buoyant spherical particles in a straight microchannel with a rectangular cross-section under Reynolds numbers ranging from 50 to 200 have been simulated using the Lattice-Boltzmann method with the discrete external boundary force. In a square microchannel, particles are focused to the equilibrium positions, each corner and center of each edge, which is in agreement with the theoretical analysis as well as the experimental observations from the literature. Inertial focusing of multiple spherical particles in rectangular microchannels with different channel aspect ratio over a wide range of Reynolds numbers have also been explored. Trains of particles are formed along the flow direction near the planar equilibrium positions of a single particle. The well-known focusing of the particles at the two centers of the long channel walls occurs at a relatively low Reynolds number, whereas additional stable equilibrium positions emerge close to the short walls with increasing Reynolds number. The equilibrium positions of particles with different sizes have also been studied, and larger particles focus more close to the centerline than the smaller ones. The verified numerical tool provides a new method to simulate the particle segregation and dynamics in inertial microfluidics, uncovers the underyling physics, and provides a design tool for inertial microfluidic devices.