VP16-14 Advanced TMR Sensor-Based Magnetrodes for High-Sensitivity Biomagnetic Field Detection
Creators: Jiamin Chen
Jiahui Luo
Zhaojie Xu
Yi Wang
Zhenhu Jin
Mixia Wang
and Xinxia Cai;
Publisher: name: IEEE
Year: 2025

The neural network of the human brain generates both electrical and magnetic signals. The magnetic fields produced by neuronal activity offer non-invasive, undistorted, and reference-free advantages for brain research. Traditional methods like Magnetoencephalography (MEG) using SQUIDs[1] and nitrogen-vacancy centers[2] have limitations in size, cost, and complexity. Spintronics-based magnetoresistance (MR) sensors, integrated into needle-shaped silicon-based substrates called "magnetrodes"[3], present a promising alternative due to their high sensitivity and compact size. Traditional magnetoresistance (MR) sensors have shown promising potential, but TMR sensors offer significantly enhanced sensitivity, making them ideal candidates for neural magnetic field measurements. This research introduces innovative TMR sensor-based magnetrodes designed for high-sensitivity biomagnetic field detection, particularly in neurological applications. Key advancements include the fabrication of magnetrodes with varying aspect ratios of the free layer, different junction shapes, and configurations to enhance the magnetic detectivity. Utilizing a custom-built magnetotransport and noise measurement system, these magnetrodes achieved a sensitivity of 22.29%/mT and an impressive limit of detection (LOD) of 300 pT/√Hz at 1 kHz. In vitro simulation experiments validate the ability of these magnetrodes to detect magnetic signals from neuronal action potentials, with firing rates matching the corresponding electrical signals. These results highlight the potential of TMR-based magnetrodes for high-resolution biomagnetic field detection, advancing our understanding of neuronal function and offering promising applications in neuroscience and biomedical engineering.References: [1] R. Hari, R. Salmelin, Magnetoencephalography: From SQUIDs to neuroscience: Neuroimage 20th Anniversary Special Edition, NeuroImage, 61 (2012) 386-396. [2] J.F. Barry, M.J. Turner, J.M. Schloss, Optical magnetic detection of single-neuron action potentials using quantum defects in diamond, Proceedings of the National Academy of Sciences, 113 (2016) 14133-14138. [3] L. Caruso, T. Wunderle, C.M. Lewis, In Vivo Magnetic Recording of Neuronal Activity, Neuron, 95 (2017) 1283-1291.e1284.
The neural network of the human brain generates both electrical and magnetic signals. The magnetic fields produced by neuronal activity offer non-invasive, undistorted, and reference-free advantages for brain research. Traditional methods like Magnetoencephalography (MEG) using SQUIDs[1] and nitrogen-vacancy centers[2] have limitations in size, cost, and complexity. Spintronics-based magnetoresistance (MR) sensors, integrated into needle-shaped silicon-based substrates called "magnetrodes"[3], present a promising alternative due to their high sensitivity and compact size. Traditional magnetoresistance (MR) sensors have shown promising potential, but TMR sensors offer significantly enhanced sensitivity, making them ideal candidates for neural magnetic field measurements. This research introduces innovative TMR sensor-based magnetrodes designed for high-sensitivity biomagnetic field detection, particularly in neurological applications. Key advancements include the fabrication of magnetrodes with varying aspect ratios of the free layer, different junction shapes, and configurations to enhance the magnetic detectivity. Utilizing a custom-built magnetotransport and noise measurement system, these magnetrodes achieved a sensitivity of 22.29%/mT and an impressive limit of detection (LOD) of 300 pT/√Hz at 1 kHz. In vitro simulation experiments validate the ability of these magnetrodes to detect magnetic signals from neuronal action potentials, with firing rates matching the corresponding electrical signals. These results highlight the potential of TMR-based magnetrodes for high-resolution biomagnetic field detection, advancing our understanding of neuronal function and offering promising applications in neuroscience and biomedical engineering.References: [1] R. Hari, R. Salmelin, Magnetoencephalography: From SQUIDs to neuroscience: Neuroimage 20th Anniversary Special Edition, NeuroImage, 61 (2012) 386-396. [2] J.F. Barry, M.J. Turner, J.M. Schloss, Optical magnetic detection of single-neuron action potentials using quantum defects in diamond, Proceedings of the National Academy of Sciences, 113 (2016) 14133-14138. [3] L. Caruso, T. Wunderle, C.M. Lewis, In Vivo Magnetic Recording of Neuronal Activity, Neuron, 95 (2017) 1283-1291.e1284.