A flowing pair of particles in inertial microfluidics

TL;DR

This study uses simulations to analyze how pairs of particles behave in inertial microfluidic channels, revealing how their interactions depend on position, flow conditions, and initial setup, with implications for biomedical applications.

Contribution

It provides detailed insights into the dynamics of particle pairs in microchannels, highlighting the roles of inertial and viscous forces and identifying different trajectory types.

Findings

Lift force profiles vary with particle positions and Reynolds number.

Three unbound trajectory types and one bound trajectory type are identified.

Damping rate of oscillations scales with Reynolds number squared.

Abstract

A flowing pair of particles in inertial microfluidics gives important insights into understanding and controlling the collective dynamics of particles like cells or droplets in microfluidic devices. They are applied in medical cell analysis and engineering. We study the dynamics of a pair of solid particles flowing through a rectangular microchannel using lattice Boltzmann simulations. We determine the inertial lift force profiles as a function of the two particle positions, their axial distance, and the Reynolds number. Generally, the profiles strongly differ between particles leading and lagging in flow and the lift forces are enhanced due to the presence of a second particle. At small axial distances, they are determined by viscous forces, while inertial forces dominate at large separations. Depending on the initial conditions, the two-particle lift forces in combination with the Poiseuille flow give rise to three types of unbound particle trajectories, called moving-apart, passing, and swapping, and one type of bound trajectories, where the particles perform damped oscillations. The damping rate scales with Reynolds number squared, since inertial forces are responsible for driving the particles to their steady-state positions.