Adhesion tunes the elasto-plastic response of biomimetic emulsions under mechanical constraint.

We study how cell-cell adhesion controls the behavior of tissues under mechanical constraint. To this end, we use biomimetic emulsions that were shown to reproduce the minimal mechanical and adhesive properties of cells in biological tissues. The adhesion between the droplets can be introduced in two different ways: nonspecific depletion attraction is induced by tuning the concentration of SDS micelles in the continuous phase; while specific adhesion is introduced by grafting the surface of the droplets with binding molecules. To study the behavior of such emulsions under an applied mechanical perturbation, we flow them through microfluidic constrictions with controlled geometries. Image analysis allows us to characterize the elasto-plastic response of the emulsions under such perturbations. Thus, we measure the level of deformation of the droplets in the channel (elastic response) and monitor irreversible droplet rearrangements (plastic response). We find that while adhesion slows down the dynamics of individual rearrangements, it does not significantly modify the large scale topology of neighbor exchanges within the packing. However, adhesion induces large scale droplet deformations, suggesting that this could be a mechanism for cell polarization in biological tissues.