Particle pairs and trains in inertial microfluidics

TL;DR

This study uses lattice-Boltzmann simulations to analyze the stability and dynamics of particle pairs and trains in inertial microfluidics, reproducing experimental distributions and revealing how defects affect wave propagation.

Contribution

It provides detailed insights into the stability, behavior, and interactions of particle trains in inertial microfluidics, supported by simulation and experimental correlation.

Findings

Cross-streamline pairs are stable and contract or expand to equilibrium.

Same-streamline pairs tend to expand and drift apart over time.

Particle distance distributions match experimental observations.

Abstract

Staggered and linear multi-particle trains constitute characteristic structures in inertial microfluidics. Using lattice-Boltzmann simulations, we investigate their properties and stability, when flowing through microfluidic channels. We confirm the stability of cross-streamline pairs by showing how they contract or expand to their equilibrium axial distance. In contrast, same-streamline pairs quickly expand to a characteristic separation but even at long times slowly drift apart. We reproduce the distribution of particle distances with its characteristic peak as measured in experiments. Staggered multi-particle trains initialized with an axial particle spacing larger than the equilibrium distance contract non-uniformly due to collective drag reduction. Linear particle trains, similar to pairs, rapidly expand towards a value about twice the equilibrium distance of staggered trains and then very slowly drift apart non-uniformly. Again, we reproduce the statistics of particle distances and the characteristic peak observed in experiments. Finally, we thoroughly analyze the damped displacement pulse traveling as a microfluidic phonon through a staggered train and show how a defect strongly damps its propagation.