Controlled fabrication of solid-shelled capsules with designed geometry sphericity

Abstract The high degree of control afforded by microfluidic techniques enables the generation of monodisperse water-in-oil-in-water (W1-O-W2) double droplets, which are transformed to solid-shelled capsules through solvent-evaporation-based microencapsulation. Experimental investigations and numerical simulations are combined to explore the developments for controlled fabrication of solid-shelled capsules with designed geometry sphericity. The designed geometry sphericity arises from the competition between solidification and shear stress generated by the shear flow field. An increasing viscosity of continuous phase resists the solidification, which contributes to improve the sphericity of the solid-shelled capsules, but intensifies the shear stress of the flow filed, which promotes the deformation of the droplets. Therefore, the continuous phase viscosity exerts a parabolic effect on the deformation of double droplets and the sphericity of the resulting capsules. Accordingly, spherical and non-spherical such as oval and ellipsoid jujube core like solid-shelled capsules can be obtained by controlling the viscosity of the shear flow field.