Electrohydrodynamic deformation and rotation of a particle-coated drop

TL;DR

This study investigates how surface-adsorbed colloidal particles influence the electrohydrodynamic behavior of dielectric drops in electric fields, revealing suppression of flow, enhanced deformation, and lowered rotation thresholds.

Contribution

It provides experimental evidence that particle coatings alter classic electrohydrodynamic phenomena, modeling the particle layer as an elastic interface to explain deformation.

Findings

High surface coverage suppresses electrohydrodynamic flow.

Particle coating enhances oblate deformation of drops.

Lowered threshold for drop tilt and rotation due to particle effects.

Abstract

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.