A reconfigurable superparamagnetic bead filter for microfluidic detection of bio-material

For a faster and more efficient sensing of highly diluted samples, up-concentration of biological species is often required. Within this framework, we here describe the design, fabrication and first experimental results of a compact microfluidic chip that uses the capture and release of micron-sized superparamagnetic beads for species up-concentration. The beads are captured out of the bypassing flow by soft-magnetic structures embedded in the microchannel that can be magnetized by an external field. Simulations of bead capture are reported for average flow speeds up to 50 mm/s that are equivalent to flow rates of 0.03 μl/s on a single channel. A comparison between the experimental results obtained with an average flow speed of 4.44 mm/s (flow rate of about 0.028 μl/s) and finite element method (FEM) simulations of the bead capture is shown. From the obtained results we can conclude that an up-scaled version of such a chip could easily scan fluids with flow rates above 1 μl/s.