The growing need for pointofcare applications in global health and personalized medicine motivates a significant reduction in the size and cost of present technologies. Current solutions use fluorescent or enzymatic labels with complex optical instrumentation that has proven difficult to miniaturize. Recently, magnetic bead labeling has emerged as an alternative solution enabling portable and lowcost platforms.
A compact and robust magnetic label detector for biomedical assaysis implemented in 0.18μm CMOS. No external magnet, reference sensor or baseline calibration is required. Detection relies on the magnetic relaxation signature of a microbead label for improved tolerance to environmental variations and relaxed dynamic range requirementCorrelated double sampling combined with offset servo loops and magnetic field modulation, suppresses the detector offset to subμT. Single 4.5μm magnetic beads are detected in 16 ms with a probability of error < 0.1%. Magnetic imaging and bead differentiation based on relaxation are demonstrated which could potentially lead to new applications.