FIELD-INDUCED STRUCTURE OF CONFINED FERROFLUID EMULSION

Abstract

Field-induced phase behavior of a confined monodisperse ferrofluid emulsion was studied using optical microscopy, light transmission, and static light scattering techniques. Upon application of magnetic field, randomly-dispersed magnetic emulsion droplets form solid structures at λ = 1.5, where λ is defined as the ratio of the dipole–dipole interaction energy to the thermal energy at room temperature. The new solid phase consists of either single droplet chains, columns, or worm-like clusters, depending on the volume fraction, cell thickness and rate of field application. For the column phase, an equilibrium structure of equally-sized and spaced columns was observed. Our measurements taken for cell thickness 5µ m ≤ L ≤ 500µ m and volume fraction 0.04 show the column spacing to be reasonably described by d = 1.49L0.34.