Anisotropic droplets with uniform internal structure prepared in batch-scale by combination of vortex mixing and phase separation

Structured fluids are attractive in material science owing to their softness, variability and excellent solubility. Anisotropic emulsions, with droplets composed by structured multiple phases, are a new class of colloidal materials due to their distinct advantages of chemical encapsulation and geometry variation. High uniformity of internal droplet structure is the premise of advanced application. A fabrication approach is investigated by combination of vortex mixing and phase separation (VP), i.e. homogenous emulsion is produced by vortex mixing two immiscible oils using a volatile co-solvent and then anisotropic emulsion is obtained by phase separation induced by the spontaneous volatilizing of co-solvent. Uniformity of droplet structure in binary, ternary and even quaternary systems is systematically studied. Numerical calculations of evaporation based on three-phase diagram are performed to illustrate the kinetic process of droplet compartmentalization . In addition, the uniform droplets are applied as templates to fabricate anisotropic porous particles. Uniformity of droplet geometry is witnessed by the standard deviation reduced more than ten times. Higher order structures including two-face Janus, three-face Cerberus, and even four faces verify the university of VP strategy. Nucleation, coalescence, Ostwald ripening, and phase separation are the main procedures of droplet compartmentalization, which is controllable based the phase diagram. Anisotropic porous particles fabricated show the significant advantages of uniform morphology and flexible regulation. The strategy would propel the application of anisotropic emulsions in fields of material synthesis, drug release, and micro-reactors.