Fully integrated detection of single magnetic beads in complementary metal-oxide-semiconductor

Microcoils are integrated with n-well Hall sensors in a complementary metal-oxide-semiconductor (CMOS) integrated circuit for the detection of individual superparamagnetic beads. The 4.2-μm-wide microcoils, generating magnetic fields of 800μT with 10mA of current, are used to polarize beads of 2.8μm in diameter. The resulting 10.8μT magnetization field induced in the bead is measured by a 4.7μm Hall sensor, stacked below the microcoil. The detection system has a sensitivity and resolution of 34V∕AT and 300nT∕√Hz, respectively. Integration of the magnetic bead detection onto a CMOS platform drastically reduces system cost, complexity, and power consumption, and marks an important milestone on the road to implementing low-cost, easy-to-use, point-of-care diagnostic assay.