"Quantitative imaging of colloidal flows"
Rut Besseling, Lucio Isa, Eric R. Weeks, and Wilson C. K. Poon, Advances in Col. Int. Science 146, 1-17 (2009)

We present recent advances in the instrumentation and analysis methods for quantitative imaging of concentrated colloidal suspensions. After a brief literature review, we describe various ow geometries for two and and three-dimensional (3D) imaging, including a 'confocal rheoscope'. This 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).