Microfluidic multiphase flows of immiscible fluids with a miscible solvent in the continuous phase

We experimentally examine the behavior of ternary fluid systems in the presence of a miscible solvent in the continuous phase. Coaxial microdevices are employed to generate a range of microflow patterns made of water-in-oil and oil-in-water dispersions over wide variations of flow rates. In particular, we investigate the relationship between solvent concentration and segmented flows characteristics and reveal a range of intriguing interfacial behaviors at ultralow interfacial tension, including spontaneous emulsification, dynamic wetting transitions and phase inversion, as well as unstable jets. This work clarifies important aspects of hydrodynamic interactions between interfacial and diffusive phenomena at the small scale.