Capillary imbibition of emulsions in thin rectangular channels

Emulsions imbibing in a capillary under transient surface-tension driven flow display an unexpected richness in droplet interactions, clustering and ordering. Droplet size and concentration effects on the droplet interactions of monodisperse oil-in-water emulsions are demonstrated by use of a thin channel to form a pseudo 2-dimensional flow. We categorize droplet-droplet and cluster-cluster interactions at the microscale and find markedly different behavior in ordering, relative phase velocity and droplet-induced interface perturbation depending on concentration and the relative size of the droplets compared to the channel height.