Colloid Quincke-electrorotation near a boundary*

The Quincke effect is an electrohydrodynamic instability that gives rise to a torque on a dielectric particle in a uniform DC electric field. In an unbounded medium, a spherical particle with conductivity and permittivity mismatch was found to undergo a Lorenz chaotic rotation (Peters et al, Chaos, 2005). Pradillo et al, Soft Matter (2019) reported a new dynamics regime, where a colloid, which initially rests on the bottom electrode, lifts off and levitates in the space of two electrodes. We analyze the Quincke rotation in this hovering state.

 We consider a spherical particle rotating near a plane electrode in a uniform electric field. The effect of the electrode is considered using the method of images. We analytically calculate the electric torque on the particle and formulate the equations describing the evolution of the rotation rate and the electric multipoles. We investigate the colloid dynamics numerically by solving the full set of evolution equations and analytically by means of asymptotic solutions for large separations from the boundary.