Pinch-off dynamics of double-emulsion droplets with/without the influence of interfacial coupling effect

Abstract

Pinch-off dynamics of double-emulsion droplets is experimentally studied. Pure liquid systems with different combinations of three-phase viscosities are considered to particularly reveal the thinning mechanisms and their variation characteristics when the interfacial coupling effect exists. The whole breakup process is analyzed at first, and the pinch-off stage governed by the interfacial tension is confirmed. The scaling law of the minimum neck width is constructed to make quantitative comparisons with the conventional theories obtained from single emulsions. The influence of the coupling effect on the thinning dynamics is discussed by sequentially varying the viscosity of one single phase of the liquid system. With the coupling effect, it is found that the rapid collapsing occurs in advance due to the superposition of the Laplace pressure differences at the minimum neck width. The thinning rate of the outer droplet follows that of the inner droplet until the breakup of the inner droplet, after which the thinning process of the outer droplet quickly coincides with the uncoupled case as the disturbances damp out by relatively high viscosity. On the contrary, the subsequent thinning dynamics would be changed when the low-viscosity liquid is used.