Induction Based Detection of Magnetic Particles Via Phase Locked Loop

This study describes the process of designing an induction based sensor for magnetic particle detection. The sensor performance is verified by the means of practical experiments. An oscillator circuit integrated with voltage comparators and phase locked loop was used to investigate the effect of magnetic particle mass on the resonance frequency of the sensor. The core of the sensing system is the circular air-core inductor which generates magnetic field and polarizes the magnetic beads in its vicinity. Differential sensing scheme is implemented to minimize environmental interfaces and suppress any low-frequency fluctuations. The sensor is resonating at 2.7MHz of frequency. The frequency shift of 142 Hz was achieved in the presence of 10μL of magnetic particles with 10nm bead size. This sensing setup can be used for molecular DNA hybridization detection and point of care diagnostics.