The Importance of Interfacial Tension in Emulsification: Connecting Scaling Relations Used in Large Scale Preparation with Microfluidic Measurement Methods

This paper starts with short descriptions of emulsion preparation methods used at large and smaller scales. We give scaling relations as they are generally used, and focus on the central role that interfacial tension plays in these relations. The actual values of the interfacial tension are far from certain given the dynamic behavior of surface-active components, and the lack of measurement methods that can be applied to conditions as they occur during large-scale preparation. Microfluidic techniques are expected to be very instrumental in closing this gap. Reduction of interfacial tension resulting from emulsifier adsorption at the oil-water interface is a complex process that consists of various steps. We discuss them here, and present methods used to probe them. Specifically, methods based on microfluidic tools are of great interest to study short droplet formation times, and also coalescence behavior of droplets. We present the newest insights in this field, which are expected to bring interfacial tension observations to a level that is of direct relevance for the large-scale preparation of emulsions, and that of other multi-phase products.