Micromagnetic Neural Stimulation and Spintronic Neural Sensing

We report our team's recent magnetic biomedical brain-related research work: 1) micromagnetic neural stimulation
$(\boldsymbol{\mu} \mathbf{MS})$
; 2) calculation of magnetic field generated by neural cells and tissues and spintronic neural sensing. First, the designing, fabrication, and testing of two micromagnetic implants - the Magnetic Pen (MagPen), a solenoid-shaped single
$\boldsymbol{\mu} \mathbf{coil}$
prototype, and the Magnetic Patch (MagPatch), a rectangular helix-shaped planar
$\boldsymbol{\mu} \mathbf{coil}$
array prototype, is discussed. The efficacy of micromagnetic activation using MagPen has been successfully tested over many rodent models. The MagPen prototype had its caveat in terms of mm-size, lack of multidimensional spatial control and activation at the cellular-level. To bridge this research gap, the MagPatch array was designed and fabricated to study
$\boldsymbol{\mu} \mathbf{MS}$
at the single-cell resolution. Second, we used FEM exemplary models and open-source computational libraries and calculated the magnetic fields generated by individual neurons and neuronal networks at micrometer distances. Our results show that the magnetic field generated by a single-neuron action potential can be detected by ultra-high sensitivity sub-pT magnetic field sensors, which opens the door to future in vivo decoding of neuronal activities through neural networks. Room temperature, high endurance, small volume and low power make spintronic sensors one of the promising candidates for neural sensing. On this aspect, the recent experimental progress for the spintronic sensors for neural sensing has been reviewed, with a specific discussion on our effort on spintronic stack design, device fabrication and detection.