A Drift-Compensated Magnetic Spectrometer for Point-of-Care Wash-Free Immunoassays using a Concurrent Dual-Frequency Oscillator

A 2x2 magnetic spectrometer array using a concurrent dual-frequency transformer-based oscillator in 65nm CMOS is presented. Concurrent dual-frequency operation allows compensation of the drift of the free-running sensing oscillator without reconfiguring to switch the frequency of oscillation, which enables wash-free magnetic label assays and single-site multiplexed spectroscopy. The spectrometer achieves a sensitivity of 0.7ppm consuming only 3.1mW per cell over a wide frequency range of 1.2-1.65/2.9-4 GHz. A biotin-streptavidin immunoassay using iron oxide magnetic nanoparticle labels is performed without any washing steps, demonstrating high sensitivity and viability for point-of-care diagnostics.