On the role of internal geometry on droplet breakup in premix membrane emulsification

Although our bodies are mostly made of water, many of the materials we eat, wear on our skin, or use to treat diseases are insoluble in water. To overcome this challenge, we make emulsions by dispersing these materials as small oil droplets in water, which can then be used for foods, cosmetics, and pharmaceuticals. Current methods to make emulsions are either energy inefficient or produce excessive heat and are therefore unsuitable for more delicate materials. In contrast, premix membrane emulsification can be used with highly sensitive materials and is energy efficient. Various types of membranes have been used to demonstrate the applicability of premix emulsification, but we currently do not understand the role of the internal membrane geometry on droplet breakup. We designed microfluidic models to mimic common structures found in these membranes to explore the forces that lead to breakup in premix emulsification. We found a unique mechanism that causes droplet breakup in membranes with corrugated pores. In these membranes, breakup is determined by a competition of capillary forces and restricted transport across narrow constrictions along the pores. By exploiting this competition, we can potentially tailor membranes for specific applications to produce low-cost emulsions.