Shear-induced deformation and interfacial jamming of solid-stabilized droplets

Abstract

We use rheo-microscopy to directly investigate the dynamics of solid-stabilized droplets subjected to shear flow of a surrounding bulk fluid. In our system, the stabilizing particles are weakly attractive through the continuous fluid phase and along the droplet interface. Under shear, droplets stabilized by these particles at near-complete surface coverage exhibit a number of previously unforeseen phenomena, including negative-then-positive deviations from the predictions of Taylor and the behavior of bare droplets, evolution toward spherocylindrical shapes, and an earlier onset of rupture than their bare counterparts, which we explain in light of the weak attractive interparticle interactions along the droplet interface. We also demonstrate the formation of long-lived anisotropic particle-coated droplets by flow cessation, and provide evidence that this is due to the formation of a jammed, disordered particle network along the interface at surface coverage lower than the starting conditions. Importantly, these newly observed phenomena are shown to be sensitive to the droplets’ initial surface coverage. Our findings provide new technologically-relevant insights into the physics of particle-coated droplets under fluidic or other external stresses, and introduce avenues for future research to better understand the roles of interparticle interactions and surface coverage in mediating the interfacial rheology of particle–laden interfaces and solid-stabilized emulsions.