Oscillation of emulsion droplet in an alternating electric field and preparation of macrocrystalline colloidal assembly

Abstract

In this study, the oscillations of fluid drops in an alternating electric field are considered experimentally. The present theoretical analysis are based upon the leaky dielectric model for eletrostatics in conjunction with the hydrodynamics in the limt of small Reynolds numbers. We reported a series of experiments to show the effect of non-Newtonian properties on the oscillation and deformation of drop in an electric field. The difference of phase between the drop oscillation and electric field oscillation were also examined. There is no theoretical approach to the dynamics of liquid drop that considers the non-Newtonian properties in an electric field. However, the leaky dielectric theory has a good agreement with the experiments of Newtonian drop so that we consider non-Newtonian drops as Newtonian drops and examine the deviation from it. In that manner, we know about non-Newtonian properties qualitatively. Additionally, the simple system of oscillation was analyzed in order to examine the shift of phase retardation which is estimated from the theory about Newtonian fluids. As approach for the application, we prepared the macrocrystalline colloidal assembly using a drop suspended in medium as confined geometry. A colloidal assembly is a packed material of nano-sized particle, which is obtained through the evaporation of water in suspension. The shape of the colloidal assembly can be controlled by electric fields and the micro-sized assembly is obtained by the breakup of the drop. The breakup occurs when the interfacial tension can no longer support the normal electric stress. The suspension that has a various concentration of the polystyrene has properties varing from Newtonian to non-Newtonian so that the mode of breakup changes with the concentration.