Effects of Flow Rates and Density Matching on the Integrity of Solid Particles Coated by Water Phase Compound Droplets during the Transport Process

Abstract

To achieve the integrity of solid particles coated by water phase (S/W/O) compound droplets, it is important to investigate the transport process of the compound droplets in the horizontal straight channel. The experimental results show that the integrity is significantly influenced by the flow rates and density difference. The water (W) phase is observed to be peeled off from the surface of the particles (polystyrene (PS) shells), mainly caused by the slip velocity of the W phase and the density mismatching among three phases. During the peeling off process, a relative motion between the solid (S) and W phases initially occurs, causing a decrease of the distance (δ) between them, and then, the PS shell is driven to pass through the W/O interface under the action of drag force and net gravity. It is also found that increasing flow rates of both phases contributes to obtaining integrated compound droplets. A boundary that separates the integrated from damaged compound droplets also exits when the fluid properties are fixed. Above the line of the boundary, compound droplets with integrity are prepared. Moreover, the absolute optimum density matching between the S and W phases is less than 0.003 g/cm 3 , while that between the W and oil (O) phases is less than 0.005 g/cm 3 .

Acoustofluidics-Assisted Coating of Microparticles

“…Pan et al utilized T-junction droplet microfluidic chips to perform particle coating where the dispersed phase (high-molecular-weight polyvinyl alcohol, H-PVA) containing polystyrene (PS) shells was sheared by the continuous phase (oil) to generate droplets. Coating was then achieved when the H-PVA was grafted to the surface of the PS shells [15], which has applications for gas retention in inertial confinement fusion experiments. In recent years, an acoustic radiant force has been applied to manipulate particles to achieve a conformal coating of microparticles and cells [16].…”