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Effects of drop-fluid interface and hydrodynamic interactions on Quincke rotation

Malika Ouriemi (Brown university), Petia Vlahovska (Brown University)

Electrohydrodynamics and electrokinetics of fluid systems

Mon 4:20 - 5:40

Barus-Holley 161

The spontaneous rotation experienced by a weakly conductive sphere immersed in a slightly more conductive liquid when submitted to a strong DC electrical fields is known as the Quincke rotation. Similar phenomena have been observed for deformable particles, such as dielectric drops immersed in a more conductive liquid. Those effects have been widely explored due to the importance of deformable particle suspensions subjected to an external electric field in physics and biophysics. To understand the Quincke rotation of systems involved in nature or industry like biological cells, or electrorheological fluids, it is necessary to take into account more complex configurations, such as drops covered by a thin shell or the presence of hydrodynamic interactions between particles. Here, we present an experimental study of two controlled configurations investigating these effects. Rotation thresholds and drop deformation were measured for a dielectric drop covered with particles and submitted to a strong electrical field. Our results show that the presence of highly conductive particles at the interface decreases the onset of rotation, indicating more complex interactions due to the presence of the shell. In addition, we investigated the Quincke rotation of two similar dielectric spheres immersed in a slightly more conducting liquid. Our results show different rotation thresholds compared to a system composed of a single sphere. They are compared with the recent theoretical and numerical studies that focused on the interactions between two particles.