Quantum‐Based Magnetic Field Sensors for Biosensing

Abstract The accurate detection of very weak biomagnetic signals with a sensitivity of fT levels and mapping nanoscale magnetic field variations are two of the most significant challenges for biosensing. Compared to the limited sensitivity and spatial resolution of traditional magnetic field sensors, quantum‐based magnetic field sensors are emerging as a promising solution. In this review, the latest developments of three representative quantum‐based magnetic field sensors, including superconducting quantum interference device (SQUID) magnetometers, spin exchange relaxation free (SERF) atomic magnetometers, and nitrogen‐vacancy centers in diamond, are summarized. Both virtues and limitations of these sensors are analyzed systematically, and typical applications in magnetocardiography, magnetoencephalography, detection of neuronal action potentials, magnetic imaging of living cells, biomedical diagnosis, etc., are presented. Furthermore, SQUIDs combined with microfluidics for magnetic immunoassay diagnostics, the chip‐scale SERF atomic magnetometers fabricated by microelectromechanical systems that offer wearable flexibility, and nanodiamonds functionalized with magnetic nanoparticles to improve the sensitivity of nanothermometers are discussed.