Preparation of monodisperse S/W/O compound droplets with thick liquid film via a dual-cross microfluidic device

Abstract Double-layer polymer shells with stringent specifications are always employed as the inertial confinement fusion (ICF) targets, which can be prepared by solidifying the solid-in-water-in-oil (S/W/O) compound droplets. A microfluidic device with a dual-cross structure is proposed to improve the quality of the resulting S/W/O compound droplets, and further, the formation process is extensively investigated. Especially, the flow regimes of multiple-encapsulation can be avoided when compared with the flow-focusing microfluidic device, and the thickness of the polyvinyl alcohol (PVA) liquid film coated onto the solid particle is also improved because of the large interval distance between sequenced solid particles. Moreover, the influences of both phases’ flow rates on the thickness of the liquid layer are also discussed. With the decrease of the flow rate ratio of the continuous phase to the dispersed phase, the thickness of the PVA liquid film rises from 55 to 383 μm, and the coefficient of variation (CV) of the liquid film thickness is about 4%. Increase the diameter of the main channel to obtain a thicker liquid film range from 122 to 648 μm. The obtained results could provide experimental guidance to prepare S/W/O compound droplets precisely and controllably with a specific thickness of the liquid layer.