Electrohydrodynamics of particle-covered drops

Brown University, Providence RI

Investigators

Abstract

CBET 1437545 This project will explore the behavior of liquid drops that have small particles adsorbed on their interfaces. When the drops are placed in an electric field, the particles on the interface can assemble into a variety of interesting structures, including particle belts that rotate and undulate around the drop. These structures can become unstable in some conditions, leading to bucking or wrinkling. The investigators will experimentally map out the structures that form as a function of fluid, particle, and electric field properties. Then, they will use the experimental results to develop a model to predict the observed instabilities. When the particles completely cover the interface of the drop, the interface resembles an elastic solid. The way the drop shape deforms in flow will be used to deduce the mechanical characteristics of the interface. The information from this project will be useful to scientists and engineers to design and process novel colloidal products such as drops with interfaces that can respond to their local environment. Electrohydrodynamic flow in leaky-dielectric liquid drops can be used to structure and manipulate colloidal particles at the drop surface. This project will establish the mechanisms of particle assembly on a drop placed in an electric field to relate particle architectures and drop behavior to control parameters such as field strength, particle and fluid properties. Experimental studies will be carried out for drops with low particle coverage to construct a phase diagram of particle structures and the influence of particle structure on drop deformation in flow will be measured. For high surface coverage drops, drop deformation will be used to determine elastic properties of the interface. A leaky dielectric model and small deformation theory will be used to relate drop deformation and elastic properties of the interface and to predict the electric field threshold for rotation of the drops as a function of surface conductivity. The research outcomes will lead to the engineering of novel colloidal-coated drops with versatile and controllable surface coverage.