Effects of interfacial tension on the stability of toroidal droplets in viscous oils

Toroidal droplets are inherently unstable in a viscous system, they can be split into several spherical droplets via Rayleigh-Plateau instability. In this paper, we investigate the dynamic behaviors of toroidal droplets in viscous oils systematically. We find that for low interfacial tension systems, the initial aspect ratio of toroidal droplets increases as the interfacial tension decreases. It suggests that interfacial tension plays a significant role in initial morphology and determines the dynamic behaviors. We further investigate the effects on the breakup dynamics by balancing viscous and interfacial tension stresses. Results indicate that surrounding viscous oils help to sustain the surface-tension-driven instability and thus stabilize it against breakup. Our systematic investigations provide novel insights into understanding breakup dynamics of toroidal droplets in viscous phases; the results could inspire methods to control toroidal droplets for various applications.