Direct Measurement of Particle Inertial Migration in Rectangular Microchannels

TL;DR

This study provides the first detailed experimental measurements of inertial particle migration in microchannels, validating a two-term asymptotic theory and challenging existing scaling assumptions.

Contribution

It introduces a novel experimental method for 3D particle tracking and validates a parameter-free asymptotic theory of inertial migration.

Findings

Migration velocities match numerical simulations

No simple scaling law for inertial forces

Experimental method enables detailed 3D particle tracking

Abstract

Particles traveling at high velocities through microfluidic channels migrate from their starting streamlines due to inertial lift forces. Theories predict different scaling laws for these forces and there is little experimental evidence by which to validate theory. Here we experimentally measure the three dimensional positions and migration velocities of particles. Our experimental method relies on a combination of sub-pixel accurate particle tracking and velocimetric reconstruction of the depth dimension to track thousands of individual particles in three dimensions. We show that there is no simple scaling of inertial forces upon particle size, but that migration velocities agree well with numerical simulations and with a two-term asymptotic theory that contains no unmeasured parameters.