The important role of electrohydrodynamics in a system of Quincke rollers

Abstract

Colloidal spheres charged superficially are expected to repel each other through electrostatic interaction. However, in systems where the spheres are confined between two charged glass surfaces, it has been seen that long-range attractive interactions can arise due to hydrodynamics, indicating that fluid flow plays a role that is important and often neglected [1]. In this project we study the role of electrohydrodynamics in a two-dimensional system of particles that are propelled by an electric field via Quincke rotation. We determine the nature and consequences of the electrohydrodynamic flows and experimentally observe that their magnitude depends on the thickness of the cell and that it increases with it. Particle clustering and alignment has also been observed and analysed.