Easy-to-assemble and adjustable coaxial flow-focusing microfluidic device for generating controllable water/oil/water double emulsions: Toward templating giant liposomes with different properties

Abstract

Herein, an optimized microfluidic device for manufacturing encapsulating water-in-oil-in-water (w/o/w) double emulsions is reported. The adjustability of the microfluidic device allows on-demand formation of oil shells with different thicknesses during the w/o/w double emulsion formation while maintaining the same core size. This was achieved by manipulation of the separation distance between the cylindrical tubes constituting the flow-focusing part of the device, the middle flow rate of the middle phase, and the outer flow rate of the continuous phase, all at the same time. By incorporating lipids in the oil shell, the w/o/w double emulsions serve as templates for the formation of monodisperse encapsulating liposomes. Thus, liposomes with different shell properties can be generated after evaporation of the oil that can be collected either separately or pooled together in a single sample batch using only one experimental step. The w/o/w double emulsions are highly monodisperse, generated with a throughput of more than 10 Hz, having water core diameters ranging from 130 to 290 μm and different oil shell thicknesses varying from 5 to 13 μm. Moreover, double emulsions with diameters down to 10 μm are reported; however, at this size, the dispersity is less controllable. The microfluidic device is composed of commercially available parts with only minor modifications required, thus, facilitating the manufacturing of encapsulating w/o/w double emulsions.