Signal amplification using magnetic bead chains in microfluidic electrochemical biosensors

We present a novel approach to increase the sensitivity of microfluidic biosensor platforms using magnetic micro-bead chains. An almost 2-fold sensitivity enhancement is achieved by introducing a magnetic field gradient along a microfluidic channel by means of a soft-magnetic lattice with lattice spacings down to 100 μm. The magnetic field gradient induces self-assembly of the magnetic beads in chains or clusters and thus improves the active contact between analyte and beads. This facile strategy significantly increases the active bead surface while allowing for complete independence of traditional biosensor materials and channel geometries, chip-reusability and shortened measurement times. Bead chain properties were validated with optical microscopy in a glass capillary and with electrochemical measurements via glucose oxidase (GOx) labels on an integrated microfluidic chip fabricated in dry-film photo resist technology (DFR).