Removal of excess interfacial material from surface-modified emulsions using a microfluidic device with triangular post geometry

We report on a microfluidic device used to create water-in-oil and oil-in-water emulsions with controlled interfacial properties in pure solvent. Functional particles, specifically lipids, surfactants, and magnetic particulates, are delivered to the emulsion surface where they assemble to form a monolayer. This is achieved by immersing the emulsions in a high concentration of the functional particles and then separating excess material from the surrounding continuous phase. Separation is achieved using only passive hydrodynamic forces. It is desirable to remove the excess material so it is neither wasted nor available to interfere with applications where the surface-modified emulsions alone are needed. The separation of the surface-modified emulsions from the excess material is achieved by a variation of pinched flow fractionation. The emulsions are forced across streamlines into a pure solvent stream, while the smaller functional particles track a single streamline into a waste port. Numerical modeling confirms the validity of this streamline rationale for separation. The emulsions built using the microfluidic device support applications in drug delivery and membrane biology studies.