Functional micro-neuroimaging with a flux-guide-enhanced magnetic microscope

We report a portable micro-neuroimaging system based on a high-sensitivity magnetic microscope that combines a cryogen-free spin-exchange relaxation-free optically pumped magnetometer (OPM) with sharp-tipped flux guides (FGs). By transmitting magnetic flux from microscopic neuronal sources to the centimeter-scale OPM while reducing the sensor stand-off distance to nearly zero, the FGs substantially enhance both sensitivity and spatial resolution, reaching approximately 20 pT/Hz and 250 μm, respectively. To demonstrate the technique, human stem cells were differentiated into motor neurons and chemically stimulated with acetylcholine to induce synchronized electrical activity. Functional activity was independently verified using noninvasive multi-electrode array measurements. The FG-OPM microscope successfully detected localized magnetic signals from the cultured motor neurons, resolving distinct spikes that correlate directly with synchronized neuronal network activity. These results establish flux-guide-enhanced OPMs as a promising platform for portable, high-resolution magnetic imaging of neuronal activity.