Microscopic rearrangements within a highly polydisperse emulsion under steady shear

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 certain industrial applications, high polydispersity describes size variability where the largest elements can be as much as ten times the size of the smallest. Our samples consist of highly polydisperse emulsions where the volume fraction between is varied between 0.5 and 0.9. Using a Rheoscope, a system that encompasses a Rheometer and a microscope, we visualize the motion of the droplets under steady shear 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.