Depletion attraction favors the elastic response of emulsions flowing in a constriction

TL;DR

This study investigates how depletion attraction influences the elastic and plastic behavior of dense emulsions flowing through microfluidic constrictions, revealing increased deformation and delayed rearrangements due to attractive forces.

Contribution

It demonstrates that depletion attraction affects the elasto-plastic response of emulsions in flow, especially increasing deformation and rearrangement delays in constricted environments.

Findings

Attractive forces increase droplet deformation in constrictions.

Depletion attraction causes spatial delays in droplet rearrangements.

No significant change in local packing fraction deformation scaling.

Abstract

We study the elasto-plastic behavior of dense attractive emulsions under mechanical perturbation. The attraction is introduced through non-specific depletion interactions between the droplets and is controlled by changing the concentration of surfactant micelles in the continuous phase. We find that such attractive forces are not sufficient to induce any measurable modification on the scalings between the local packing fraction and the deformation of the droplets. However, when the emulsions are flown through 2D microfluidic constrictions, we uncover a measurable effect of attraction on their elasto-plastic response. Indeed, we measure higher levels of deformation inside the constriction for attractive droplets. In addition, we show that these measurements correlate with droplet rearrangements that are spatially delayed in the constriction for higher attraction forces.