6533b82cfe1ef96bd128ff1b

RESEARCH PRODUCT

Rivalry of diffusion, external field and gravity in micro-convection of magnetic colloids

Guntars KitenbergsAndrejs Cebers

subject

010302 applied physicsConvectionGravity (chemistry)Materials scienceFluid Dynamics (physics.flu-dyn)Mixing (process engineering)FOS: Physical sciencesPhysics - Fluid Dynamics02 engineering and technologyRayleigh numberMechanicsCondensed Matter - Soft Condensed Matter021001 nanoscience & nanotechnologyCondensed Matter Physics01 natural sciencesElectronic Optical and Magnetic MaterialsMagnetic fieldPhysics::Fluid DynamicsGravitation0103 physical sciencesSoft Condensed Matter (cond-mat.soft)Diffusion (business)0210 nano-technologyDimensionless quantity

description

Magnetic fields and magnetic materials have promising microfluidic applications. For example, magnetic micro-convection can enhance mixing considerably. However, previous studies have not explained increased effective diffusion during this phenomenon. Here we show that enhanced interface smearing comes from a gravity induced convective motion within a thin microfluidic channel, caused by a small density difference between miscible magnetic and non-magnetic fluids. This motion resembles diffusive behavior and can be described with an effective diffusion coefficient. We explain this with a theoretical model, based on a dimensionless gravitational Rayleigh number, and verify it by numerical simulations and experiments with different cell thicknesses. Results indicate the applicability and limitations for microfluidic applications of other colloidal systems. Residual magnetic micro-convection follows earlier predictions.

yearjournalcountryeditionlanguage
2019-08-14Journal of Magnetism and Magnetic Materials
https://doi.org/10.1016/j.jmmm.2019.166247