Microscopic rearrangements within a highly polydisperse emulsion under steady strain

To study how droplets rearrange during a flow of a highly polydisperse material, we apply continuous strain to an oil-in-water emulsion. In both nature and industrial applications, one often encounters particle size distributions with high size variability. To study this, our samples are highly polydisperse emulsions, where the largest droplets are as much as ten times the size of the smallest. Using a Rheoscope, a system that encompasses a Rheometer and a microscope, we visualize the motion of the droplets under steady strain with the aim of producing plastic rearrangements.

While large droplets predominately move with the mean flow, smaller droplets have a more complex non-affine motion impacted by interactions with the larger droplets. To analyze this behavior, we employ several approaches, including tracking changes in nearest neighbors and measuring local strain. Our experimental results agree with previously performed simulations in our lab, advancing our understanding of the behavior of highly polydisperse media under shear.