Stable, biocompatible lipid vesicle generation by solvent extraction-based droplet microfluidics

In this paper, we present a microfluidic platform for the continuous generation of stable, monodisperse lipid vesicles 20-110 μm in diameter. Our approach utilizes a microfluidic flow-focusing droplet generation design to control the vesicle size by altering the system's fluid flow rates to generate vesicles with narrow size distribution. Double emulsions are first produced in consecutive flow-focusing channel geometries and lipid membranes are then formed through a controlled solvent extraction process. Since no strong solvents are used in the process, our method allows for the safe encapsulation and manipulation of an assortment of biological entities, including cells, proteins, and nucleic acids. The vesicles generated by this method are stable and have a shelf life of at least 3 months. Here, we demonstrate the cell-free in vitro synthesis of proteins within lipid vesicles as an initial step towards the development of an artificial cell.