Isomagnetophoresis to discriminate subtle difference in magnetic susceptibility.

We report an improved magnetophoretic method, isomagnetophoresis, employing the magnetic susceptibility gradient across a microfluidic channel applied by magnetic field, and we have successfully discriminated the polystyrene (PS; 14.78 ± 0.20 μm in diameter), poly(methyl methacrylate) (PMMA; 15.00 ± 0.77 μm) and borosilicate (BS; 14.01 ± 1.00 μm) microspheres, where PS and PMMA particles have similar diamagnetic susceptibility that cannot be distinguished by conventional magnetophoresis. This platform can be applied to label-free discrimination of the biological cells and nanotubes.