  A dielectric drop suspended in conducting liquid and subjected to an uniform
electric field deforms into an ellipsoid whose major axis is either
perpendicular or tilted (due to Quincke rotation effect) relative to the
applied field. We experimentally study the effect of surface-adsorbed colloidal
particles on these classic electrohydrodynamic phenomena. We observe that at
high surface coverage (>90%), the electrohydrodynamic flow is suppressed,
oblate drop deformation is enhanced, and the threshold for tilt is decreased
compared to the particle-free drop. The deformation data are well explained by
a capsule model, which assumes that the particle monolayer acts as an elastic
interface. The reduction of the threshold field for rotation is likely related
to drop asphericity.
