Controlled movement of superparamagnetic bead rows for microfluid mixing

The controlled movement of magnetic beads trapped on a surface in the moving inhomogeneous stray fields of moving domain walls between artificial domains of exchange bias layer systems has been applied for mixing of two aqueous fluids in a microfluidic device of small volume. The mixing of the two fluids can be considerably accelerated by transporting full rows of beads and use them as micro stirrers. The mixing speed in the current experiment is tripled in the first 6 min of mixing as compared to normal diffusion even for ratios of 250 between container height and bead diameter.