An Oscillator-Based CMOS Magnetosensitive Microarray Biochip With On-Chip Inductor Optimization Methodology
This paper presents a high sensitivity oscillator-based CMOS magnetosensitive microarray biochip to detect clinical biomarkers in human samples and provide accurate information to diagnose human diseases. To increase the detection sensitivity, dynamic detecting range, and target number, a general methodology of designing an on-chip inductor with high quality factor, moderate size, and uniform surface magnetic field distribution is proposed, which meets all the electrical, magnetic and actual application requirements simultaneously, and also provides useful guidance for other oscillator-based magnetosensitive biochip design. As an implementation example, a microarray biochip with 14 sensor units in an area of  $2.3 \times 1.9\,\,\text {mm}^{2}$  is implemented in a 180-nm RF CMOS process to verify the biological sensing scheme and the correctness of the proposed theory and simulation. Finally, experiments using magnetic nanoparticles and cTnI were performed on our designed immunoassay detection system, which integrates the oscillator-based biosensor, microfluidic chip and immunoassay reagent into one platform for the first time, and the experimental results show a limit of detection of 50 pg/mL corresponding to 2.17 pM with a biological dynamic detecting range of 60 dB, proving the suitability of the biochip for quantitative analysis in practical medical diagnostics.