Ultralow Noise Orthogonal Fluxgates Enabling Weak Magnetic Field and Biomolecular Detection

Area of Science:

• Magnetometry
• Biosensing
• Materials Science

Background:

• Conventional magnetic sensors are limited by intrinsic noise, hindering ultra-weak biomagnetic signal detection.
• Orthogonal fluxgates (OFGs) offer high signal-to-noise ratios but are still affected by 1/f noise and magnetic fluctuations.

Purpose of the Study:

• To develop a low-noise orthogonal fluxgate sensor mitigating existing noise limitations.
• To enhance the performance of OFGs for sensitive detection of ultra-weak biomagnetic signals in biosensing.

Main Methods:

• Designed a novel CoP/Ag composite magnetic core with an amorphous-nanocrystalline dual phase.
• Integrated the magnetic core with a closed-loop feedback circuit for enhanced performance.
• Utilized an immunomagnetic bead assay with Alpha-fetoprotein (AFP) as a model biomarker.

Main Results:

• Achieved a noise floor of 8 pT/√Hz at 1 Hz, significantly reducing low-frequency magnetic loss.
• Demonstrated reliable detection of ultralow-concentration magnetic-bead signals.
• Obtained a linear response for AFP detection from 50 fg mL⁻¹ to 100 ng mL⁻¹ with a detection limit of 50 fg mL⁻¹.

Conclusions:

• The developed low-noise OFG sensor effectively overcomes conventional limitations in weak magnetic field detection.
• The sensor shows strong potential for applications in biosensing, geomagnetic measurements, and other weak field detection scenarios.
• The improved sensitivity and detection limits pave the way for advanced noninvasive diagnostic tools.