Controlled counter-flow motion of magnetic bead chains rolling along microchannels
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We demonstrate controlled transport of superparamagnetic beads in the opposite direction of a laminar flow. A permanent magnet assembles 200 nm magnetic particles into about 200 μm long bead chains that are aligned in parallel to the magnetic field lines. Due to a magnetic field gradient, the bead chains are attracted towards the wall of a microfluidic channel. A rotation of the permanent magnet results in a rotation of the bead chains in the opposite direction to the magnet. Due to friction on the surface, the bead chains roll along the channel wall, even in counter-flow direction, up to at a maximum counter-flow velocity of 8 mm s−1. Based on this approach, magnetic beads can be accurately manoeuvred within microfluidic channels. This counter-flow motion can be efficiently be used in Lab-on-a-Chip systems, e.g. for implementing washing steps in DNA purification.
KeywordsMagnetic beads Lab-on-a-chip Transport Handling
- Karle M, Miwa J, Czilwik G, Auwärter V, Roth G, Zengerle R, von Stetten F (2010) Continuous microfluidic DNA extraction using phase-transfer magnetophoresis. Lab Chip. doi: 10.1039/C0LC00129E