Coating of solid particles with liquid layer by microfluidics

A simple, low-cost and reliable method for coating of solid particles with liquid layer, namely formation of S/W/O compound droplets, is proposed and demonstrated experimentally via a vertical microfluidic T-junction device. At low flow rate ratio of oil (O) to water (W) phase, S/W/O compound droplets containing two solid cores are observed. With the increase of the flow rate of oil phase, S/W/O compound droplets with one solid core inside, also called single encapsulation, can be obtained. In single encapsulation, three typical flow regimes, which are squeezing regime, dripping-like regime, and jetting-like regime, can be quantitatively distinguished by the flow rates of both phases. S/W/O compound droplets, fabricated in the dripping-like regime, show a high monodispersity. Finally, polystyrene coated with polyvinyl alcohol layer (PS-PVA double-layer shells), used as a fuel container in inertial confinement fusion (ICF) experiments, can be successfully prepared via solidification of such compound droplets.