Microfluidic preparation and structure evolution of double emulsions with two-phase cores

In this work, we developed a simple capillary microfluidic device to prepare double emulsions with two-phase cores. We can control the structure and size of double emulsions by changing four-phase flow rates. Based on the formation of these four-phase double emulsions, we investigated the structure evolution of the double emulsions for different systems, and successfully obtained different multiple emulsions with four typical inner structures, as a separately engulfing structure, triple emulsion structure, Janus-engulfing structure, and inner-Janus structure. The equilibrium morphologies of the double emulsions could be estimated by using the relationship of interfacial tension between different phase fluids. Remarkably, the physics of evolution of double emulsions with two-phase cores in a microfluidic device allows the synthesis of microparticles with new morphologies and more applications in encapsulation of multiple active substances.