Microscopic details of the flow of highly polydisperse emulsions

Soft amorphous materials such as emulsions have liquid-like structure, but their flow properties differ from liquids due to the discrete nature of the droplets. These materials flow through local rearrangements of small group of particles. To understand this process, many prior studies used samples composed of particles of one size or of two similar sizes. In nature, however, many materials are highly polydisperse, with particle sizes varying ten times or more. We use confocal microscopy to track the 3D trajectories of droplets in a flowing highly polydisperse emulsion. The emulsions are pumped through a gradually narrowing chamber to drive droplet rearrangements. The experimental results indicate that in general, the smaller droplets have more disordered trajectories due to their need to move around the larger droplets, which are more likely to follow the mean flow due to their larger size.