(237u) Fabrication of Solid in Water in Oil (S/W/O) Compound Droplets Via a Microfluidic T-Junction Device

Abstract: Herein we describe a versatile strategy for fabricating of S/W/O compound droplets by means of cross-flowing shearing technique in a microfluidic T-junction device. In the experiment, S/W/O compound droplets with two solid cores inside were observed with high flow rate in main channel but low flow rate in side channel. Particularly, by adjusting the flow rate ratio of oil (O) to water (W) phases, single encapsulation which contains only one solid core can be obtained controllably. Three kinds of flow patterns in single encapsulation, namely squeezing regime, dripping-like regime and jetting-like regime, can be distinguished by the flow rates in the side and main channels. At low flow rates in the main and side channels, the squeezing regime occurred, in which the pressure drop is the dominant force to break off the neck. With increasing the flow rate in the main channel, a dripping-like regime can be identified. A high flow rates in the side and main channel contribute to the formation of the jetting-like regime, in which the inertia force cannot be ignored. In addition, regimes in the flow pattern diagram dependent on flow rates in the side and main channel are obtained. The formed S/W/O compound droplets in squeezing and jetting-like regime show a wide size distribution. However in dripping-like regime, the resulting S/W/O compound droplets have a high monodispersity. Further, by solidification of the S/W/O compound droplets, the polystyrene (PS) - polyvinyl alcohol (PVA) double-layer shells can be successfully prepared. This new technique for the fabrication of S/W/O can not only be applied in the field of microfluidics but also in chemical/biological engineering (e.g., drug delivery, bioreactors, etc.), as well as burgeoning inter-discipline such as inertial confinement fusion (ICF) experiments.