Toward a magnetoresistive chip cytometer: Integrated detection of magnetic beads flowing at cm/s velocities in microfluidic channels

Abstract

This work describes an integrated device comprising microfluidic channels and incorporated spin-valve sensors sensitive enough to count, determine the magnetic orientation, flowing height, and speed of single micron-sized magnetic beads moving with velocities of 8–35 mm/s. Sensor signals of 3–100 μVp-p correspond to bead moments at different directions indicating a physical rotation of the beads and a slow response (seconds) of the bead moment to magnetizing field changes.