Quantitative imaging of colloidal flows

TL;DR

This paper reviews recent advances in quantitative imaging techniques for concentrated colloidal suspensions under flow, introduces new particle tracking algorithms, and demonstrates applications in various flow geometries.

Contribution

It introduces two new algorithms for reliable particle tracking in non-uniform flows, enhancing accuracy over existing methods.

Findings

Successful application of methods to three different flow geometries.

Enhanced particle tracking accuracy in flowing colloidal systems.

Integration of confocal microscopy with rheometry for microstructural analysis.

Abstract

We present recent advances in the instrumentation and analysis methods for quantitative imaging of concentrated colloidal suspensions under flow. After a brief review of colloidal imaging, we describe various flow geometries for two and and three-dimensional (3D) imaging, including a `confocal rheoscope'. This latter combination of a confocal microscope and a rheometer permits simultaneous characterization of rheological response and 3D microstructural imaging. The main part of the paper discusses in detail how to identify and track particles from confocal images taken during flow. After analyzing the performance of the most commonly used colloid tracking algorithm by Crocker and Grier extended to flowing systems, we propose two new algorithms for reliable particle tracking in non-uniform flows to the level of accuracy already available for quiescent systems. We illustrate the methods by applying it to data collected from colloidal flows in three different geometries (channel flow, parallel plate shear and cone-plate rheometry).