We aim to combine recent breakthroughs in magnetic sensing technology and functional neuroimaging system design for beyond state-of-the-art investigations of the human brain in health and disease.
The technical breakthrough consists of nano-fabricated high critical-temperature (high-Tc) junctions that yield superconducting quantum interference device (SQUID) magnetometers that are simpler to fabricate, enable more flexibility in design, and are more sensitive to magnetic fields as compared to the state-of-the-art. There are two state-of-the-art approaches to low-noise high-Tc SQUID magnetometers: bicrystals and step-edges. While both have been developed and refined since the 1980s, they require multilayer and/or multi-chip configurations in order to reach high sensitivity.
Such technical challenges limit fabrication yield and design flexibility. As such, widespread utilisation of high-Tc SQUIDs has been limited, especially when compared to their low critical temperature (low-Tc) counterparts. Our recent development of a new high-Tc SQUID fabrication process, namely grooved Dayembridges, overcomes these limitations because it consists of patterning of a single high-Tc film while meeting—or exceeding—the low-noise capabilities of the state-of-the-art. The elegantly simple fabrication approach enables unique design flexibility. It furthermore lends itself to volume production for beyond state-of-the-art single- and multi-channel magnetometer systems that can meet the market need in non-destructive evaluation, geomagnetism, and biomagnetism. The latter is of high relevance for medical imaging: we target neuroimaging with magnetoencephalography (MEG) herein.
The neuroimaging advancement is enabled by the moderate (T~77 K) operating temperature of our highly-sensitive SQUIDs such that they can be placed in close (within 1 mm) proximity of the head surface where neuromagnetic signals are stronger and imaging resolution is improved. The state-of-the-art in MEG today is based on low-Tc SQUIDs: as the name implies, such sensors operate at extreme cryogenic temperatures (T~4 K) and therefore require significant overhead in terms of thermal insulation and expensive liquid helium. The sensors inside MEG systems on the market today are roughly 2 cm from the head surface and systems consume some 100 litres of liquid helium per week. Because the magnetic fields generated by neural activity decay rapidly as a function of distance from the sources (i.e., the electrical activity of neurons in the brain), MEG systems suffer from low signal levels and spatial resolution. By densely packing our highly sensitive magnetomers around the scalp surface, we detect stronger signals with improved spatial sampling. We can furthermore replace expensive and scarce liquid helium with cheap and abundant liquid nitrogen. As such, we can achieve a quantum leap in neuroimaging capabilities—at a lower cost—as compared to the state-of-the-art.