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Single Magnetic Bead Detection in a Microfluidic Chip Using Planar Hall Effect Sensor
In this study, we fabricate an integrated microfluidic chip with a planar Hall effect (PHE) sensor for single
magnetic bead detection. The PHE sensor was constructed with a junction size of 10 μm × 10 μm using a
trilayer structure of Ta(3 nm)/NiFe(10 nm)/Cu(1.2 nm)/IrMn(10 nm)/Ta(3 nm). The sensitivity of the PHE
sensor was 19.86 μV/Oe. A diameter of 8.18 μm magnetic beads was used, of which the saturation
magnetization was ~2.1 emu/g. The magnetic susceptibility χ of these magnetic beads was calculated to be ~0.14. The diluted magnetic beads solution was introduced to the microfluidic channel attributing a single bead flow and simultaneously the PHE sensor voltage was measured to be 0.35 μV. The integrated microchip was able to detect a magnetic moment of 1.98 × 10−10 emu.