Visualization study on solid-core encapsulation behaviors of double emulsion in a flow-focusing microchannel

Abstract

A flow-focusing microfluidic chip based on assembled capillary method is developed and the solid-core encapsulation behaviors of double emulsion in a flow-focusing microchannel are visually observed via high-speed microscopic imaging system. The experimental results identify the encapsulation of single, double and triple cores in a flow-focusing microchannel arising from the competition among the inertial force of inner phase, the shear force of outer phase fluid, and the interfacial tension. In addition, the solid-core encapsulation of double emulsion in flow-focusing microchannel is either in the stable state or in the transition state, depending on the flow rates of inner and outer phase fluid. The stable microencapsulation includes the stable single-core, double-cores and triple-cores encapsulation states, while the transition microencapsulation includes the single-double-cores and double-triple-cores transition encapsulation state. Irrespective of encapsulation state, the solid-core encapsulation process can be classified into four stages, including entering, neck stretch, neck shrinking and breakup.