(660b) A New Coaxial Capillary Pendant Drop Method to Study the Interfacial Tension and Interfacial Rheology of Double Emulsion Formulations

Double emulsions (DEs), which are highly structured multi-phasic systems of two immiscible fluids (viz. water and oil) show significant potential in the diverse fields of applications including food, pharmaceuticals, and cosmetics. Though microfluidic technologies offer an excellent control over the fluid flow that enables the production of highly monodisperse DE drops with well-defined internal composition, a better understanding of the dynamics of the droplet formation is still essential to reproducibly generate DEs with desired properties. Here, we study a static pendant drop containing a single or multiple inner droplets to measure the surface tension and interfacial rheology that can be correlated with DE formulation parameters. We can produce highly monodisperse DEs using a co-axial capillary pendant drop set-up using water and representative oils (dodecane and dichloromethane). It is found that both the surface tension () and the Gibbs elasticity (E_G) are function of the droplet formulation parameters such as the size (Di) and volume fraction (Ï•_i) of the internal droplets contained in the middle phase droplet, and concentration of the inner (C_i) and middle phases (C_o). Such parameters can be independently controlled by device geometry or process parameters such as flow rate.