Electric field mediated droplet centering

Abstract

Double emulsion droplets subjected to a uniform ac electric field self-assemble into highly concentric structures via the dipole/dipole force if the outer droplet has a higher dielectric constant than the suspending liquid. The dielectric constant of the inner droplet has no influence. To minimize field-induced droplet distortion, the liquids must be density matched to ∼0.1%. Centering of ∼3 to 6 mm diameter droplets is achieved within ∼60 s for field strengths of ∼104 Vrms/m in liquids of viscosity ∼10 cP. Effective centering depends strongly on frequency if the outer shell is conductive.