Dead-end emulsification in the auto breakup regime

An emulsion is a mixture of two immiscible solutions, most often in the form of droplets of one liquid in the bulk phase. Membrane emulsification is a suitable technique for making uniform droplets in the bulk solution. Cross-flow, co-flow and dead-end membrane emulsification techniques have been developed to investigate droplet formation. However, the fluid dynamics of these droplet formations are still not well understood.


A new model explains the droplet formation in the auto breakup regime in dead-end emulsification. This model is based on breakup by surface tension and internal pressure differences. The Laplace pressure of a growing droplet decreases while the applied pressure on the membrane stays the same. The radius of dispersed phase cylinder inside the nozzle decreases when the internal pressure of the droplet decreases below the Laplace pressure of dispersed phase cylinder. The pressure difference across the membrane leads to a flux of the dispersed phase through the capillary. The droplet becomes infinitely large when the dispersed phase flux exceeds a critical flux. A new model is investigated and verified by following the process of auto breakup in a glass capillary. From these experiments we find that auto breakup occurs inside the capillary (Figure 1). We also find that droplets become very large when applying a large dispersed phase flux. We conclude that the experimental data agree with this model and further development of this model looks promising.

Figure 1: Auto breakup inside a capillary. The dispersed phase is sunflower oil and the continuous phase is 1% (w/v) Tween-20 in water.

Fields of interests:

Emulsification techniques, fluid dynamics and interfacial chemistry.