Droplet rearrangements during slow compression of a jammed 2D emulsion

We experimentally study droplet rearrangements within an evaporating quasi-two-dimensional emulsion system. Our samples are oil-in-water emulsions confined between two close-spaced parallel plates, so that the oil droplets are deformed into pancake shapes. In this system, water slowly evaporates from an open edge of the chamber and, as a consequence, the volume fraction of oil droplets gradually increases. By means of microscopy, we analyzed the packing structure of the droplets and their rearrangement motions. Following the methods of [Rieser et al., PRL 116, 088001 (2016)], at each time we construct the radial Voronoi tesselation. We then calculate the Voronoi cell anisotropy vectors which point from the center of each droplet to the corresponding Voronoi cell centroid. This identifies void spaces where droplets, which bias droplet rearrangement motions. In particular, T1 rearrangement events are oriented to induce droplet motion that fills in the voids.