A novel magnetic microfluidic platform for on-chip separation of 3 types of silica coated magnetic nanoparticles (Fe3O4@SiO2)

This paper presents a compact and cost effective method for on-chip separation of silica-coated magnetic nanoparticles (SMNPs) with different hydrodynamic size. Three types of SMNPs (Fe3O4@SiO2) with the same magnetic core but with different thickness of silica shells were successfully separated using the developed microfluidic platform. The innovative aspect of the presented separation method is that the induced velocity on the three different types of SMNPs while imposed to the same magnetic field gradient in a static fluid is inversely proportional to their overall, non-magnetic volume. This is due to the enhanced Stokes' drag force exerted on the nanoparticles (NPs) resulting from their greater volume. Detected differences in velocity between the NPs indicate the change in their hydrodynamic size (due to the different thickness of silica shells) in the static liquid sample. The developed size recognition platform could provide information on the hydrodynamic size of NPs much faster and cheaper than conventional laboratory equipment such as transmission electron microscopy (TEM) and dynamic light scattering (DLS).