Liquid-liquid phase separation within a co-axial flow system

In this work, we study liquid-liquid phase separation between two partially miscible streams, inside a co-axial glass capillary microfluidic device. A jet of poly(ethylene glycol) diacrylate (PEGDa) and glycerol is flowed in a continuous phase of a highly concentrated glycerol solution. As the two-streams flow downstream along the length of the channel, structures near the fluid-fluid interface evolve due to liquid-liquid phase separation, triggered by transport of water from the inner stream towards the outer stream. By tuning both flowrate and the initial composition of the system, we quantify the size, wavelength, and orientation of the structures that evolve as a function of position downstream along the length of the channel. Furthermore, via photopolymerization of the PEGDa rich jets at different positions along the length of the channel, we generate microfibers with different textures. Understanding the dynamic process of liquid-liquid phase separation within controlled flows may have important implications for design of materials with unique functionalities.