Development of Quantum Magnetic Tunneling Junction Sensor Arrays for Brain Magnetoencephalography (MEG) under Natural Settings

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Project Summary The long-term objective of this project is to develop a revolutionary quantum mechanical solid-state magnetometer designed to non-invasively detect femtoTesla (fT) scale magnetic fields derived from the brain’s electrical activities during natural human experiences. The project has been designed to address the vision of the NIH Brain Initiative: Transformative Brain Non-invasive Imaging Technology Development. The core component of the magnetometer is a quantum-based magnetic tunnel junction (MTJ), a nanoscale sensing device with potentially unprecedented sensitivity and performance. Through a series of steps and interdisciplinary collaboration, this project is expected to increase the sensitivity of the current MTJs by several orders of magnitude and to develop triaxial MTJ sensors capable of recording the brain's magnetic fields with the highest information density. Once the desired sensitivity is achieved, the project will build a whole-head 300-channel magnetoencephalographic (MEG) system based on MTJs, which can operate fully untethered, without the need for an expensive magnetically shielded room or nulling coils. By design, the sensors will be immune to natural head motion, further enabling the system to function in natural environment. The project will address several challenges in designing and producing sensors that can detect magnetic fields as low as 50 fT. First, the project will improve the detectability of current prototype sensors by several orders of magnitude by using a series of innovative approaches in sensor design, atomic engineering, fabrication, and noise reduction. Second, the project will design and package triaxial sensors that can simultaneously measure tangential and radial magnetic fields. Third, the project will reduce the size of the sensors by more than five times compared to other technologies, so that more sensors can be implemented on a full-head helmet to improve spatial resolution and localization. Finally, and importantly, the project will increase the field dynamic range of the sensors over the technologies based on OPM (optically pumped magnetometer) and SQUID (superconducting quantum interference device), so that the MTJ-MEG system can operate without the need of magnetic shielding to allow real-world applications. Once these groundbreaking MTJ sensors are developed, the project will integrate the MTJ-MEG system architecture and make it available for verifying performance versus competing technologies. The project will use the MTJ-MEG system to assess brain related signals during sensory stimulation, cognitive processing, and motor actions. If successful, this project will develop a transformative MTJ-MEG system with unpresented levels of performance to produce a dynamic picture of the brain under natural settings covering the whole lifespan.