(205c) Using Shear Flow to Assist the Coating of Microparticles with Nanoparticles

Previous studies involving dry powders and static aqueous solutions have demonstrated dramatic changes in aggregation and flowability properties when microparticles are coated with nanoparticles, particularly in the presence of significant charge interactions between the two particle types. In this work, we examine the influence of shear flow on the extent and morphology of coating during mixing of microparticles and nanoparticles of opposite charge in an aqueous solution. Shear flow is generally presumed to counteract aggregation and therefore may allow higher particle concentrations to be combined than in a static solution.

The experimental system involves cationic chitosan gel nanoparticles and anionic alginate microparticles mixed in a narrow-gap, concentric cylinder Couette cell. Optical and electron microscopy are used to characterize the resulting population of multiscale particles. The impact of the mixture composition and average shear rate will be discussed, as well as steady shear compared to oscillatory shear flow. Furthermore, using known shear-induced particle migration rates for the geometry, we can also explore tailoring the flow to create the particle segregation conditions that are best suited for the assembly of multiscale particles.