FIG. 4.

(a) Schematic representation and definition of the different parameters: D is the distance between the two permanent magnets — the microchannel being in the middle — and d is the vertical shift of the channel position regarding half the magnets height. (b) Evolution of the $|(\mathit{B}·\nabla )\mathit{B}|$ term across the channel width as D is varied, for d = 0 mm. (c) Evolution of the $|(\mathit{B}·\nabla )\mathit{B}|$ term across the channel width as d is varied, for D = 10 mm.