Reducing Taylor dispersion in capillary laminar flows using magnetically excited nanoparticles: Nanomixing mechanism for micro/nanoscale applications

Magnetic nanoparticles (MNPs) suspended in liquids lend themselves to manipulation at distance using suitable external magnetic fields to shuttle anchored catalysts, enzymes or drugs. Despite their widespread use in (bio)catalysis/separation or drug delivery – applications where nanoscale mixing can be a substantive issue–, the use of MNPs to promote nanomixing has not yet been explored. We report a new magnetically-induced nanoconvection mechanism that will enhance transport beyond the limits of molecular diffusion. This mechanism is demonstrated using a Taylor dispersion capillary flow cell where MNPs are excited using low-frequency transverse rotating magnetic fields. Forcing MNP spin direction to align parallel to flow in opposition to fluid vorticity is shown to intensify lateral mixing far more rapidly than molecular diffusion. This nanomixing mechanism could find applications in (bio)chemical engineering, medical and pharmaceutical areas where transport intensification is crucial.

► MNPs maneuvered at inaccessible spatial scales using external magnetic fields. ► Spinning MNPs under RMF transfers momentum to the surrounding liquid molecules. ► Excited MNPs attenuate axial dispersion in Taylor dispersion test in capillary. ► Spinning MNPs flatten laminar velocity profile in capillary tube toward plug flow. ► Induced nano-convection intensifies transport beyond molecular diffusion.