Velocity oscillations in confined channel flows of concentrated colloidal suspensions

TL;DR

This study investigates how concentrated colloidal suspensions flow through micro-channels, revealing pressure-driven oscillations linked to confinement effects and shear thickening at the particle level.

Contribution

It provides new insights into the dynamics of confined colloidal flows, especially the transition from fluctuations to regular oscillations at specific confinement ratios.

Findings

Flow rate fluctuations observed at certain confinement ratios.

Regular oscillations emerge at higher confinement ($a/ar{D} \,\simeq 20$).

Oscillations linked to solvent-permeation and shear thickening effects.

Abstract

We study the pressure-driven flow of concentrated colloids confined in glass micro-channels at the single particle level using fast confocal microscopy. For channel to particle size ratios $a/\bar{D} \lesssim 30$, the flow rate of the suspended particles shows fluctuations. These turn into regular oscillations for higher confinements ($a/\bar{D} \simeq 20$). We present evidence to link these oscillations with the relative flow of solvent and particles (permeation) and the effect of confinement on shear thickening.