Interface controls using physicochemical changes at emulsions

Abstract

In an emulsion-based system, utilizing physicochemical changes can be an effective way to control an interface and alter a behavior of the emulsion since it is relatively easy to change the chemical potential and interfacial tension compared to either applying external forces or adjusting overall temperature and pressure of the system. By controlling the interface physically, chemically, and electrically through physicochemical changes in the emulsion, the new followings can be achieved. First, when diffusion-induced crystallization starts at the interface in an emulsion containing saturated salt, spherical capsules, rather than the unique three-dimensional shape of the salt crystals, are formed through self-assembly of plate-like nanostructures aided by elasticity of the crystallites and capillarity of the emulsion. Second, by adding polymer and acid to a liquid metal-based emulsion system, the droplets merge to have flat and uniform aggregates. After the emulsion evaporates, the colloidal deposition pattern electrically activates without a post process, and serves as a flexible electrode having excellent electrical conductivity even on a deformable substrate. Third, size of liquid metal droplets generated at a microfluidic channel with a junction can be additionally controlled by applying a voltage inside the channel filled with various aqueous electrolyte solutions having different concentrations of electrolyte and water. This dissertation describes the working mechanism of each phenomenon, including a hydrodynamic point of view, and suggests how they can be practically applied.