A Hybrid Superconductor/Nanomechanical Magnetic Field Detector for Biomagnetism

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Contents of the Talk

Current commercial setups for magnetoencephalography (MEG) use helmets comprising low Tc SQUIDs. SQUID sensors are barely robust to static and pulsed magnetic fields, such as the ones used in Ultra-Low Field Magnetic Resonance Imaging (MRI) and especially Transcranial Magnetic Stimulation (TMS). For this reason, integration of MEG with these techniques in a unique system at present has not yet been achieved. Our purpose is to develop a magnetic field sensor with sensitivity of the order of 10fT/sqrt(Hz) to measure the magnetic field of the human brain and at the same time quickly recovering in a strong applied field (» 1 T) [1]. This sensor would be suitable for an on-scalp MEG system integrated with multiple imaging modalities to image brain activity and connectivity with high spatial and temporal resolution. We are developing a hybrid device by coupling a high-Q MEMS/NEMS resonator having a magnetic element to a high-Tc superconducting magnetic field focuser in series to a pick-up loop that collects the external magnetic field. The biomagnetic field induces a supercurrent in the loop, which has a geometry designed to generate a strong non-uniform magnetic field in the proximity of the magnetic element of the NEMS resonator [2]. The resonance frequency of the resonator is modified by this magnetic coupling and detected by a fiber-optic interferometer. Optomechanical detection of biomagnetic fields has the advantage of reducing the crosstalk between the channels with respect to electrical detection. This feature requires the development of a cheap, robust and scalable optomechanical platform for a future NEMS-based helmet. I discuss the basic working principle of this hybrid sensor and the advancements made so far for the realization and characterization of the first device prototypes as well for the realization of the optomechanical platform that will host the first magnetometer for characterization in operative environment.

References

[1] www.oxinems.eu. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 828784.

[2] Patent no. US11415642 "A device for sensing a magnetic field".

Short CV

Luca Pellegrino is senior researcher at the SPIN institute of the National Research Council of Italy. Since his degree in physics (2000), he worked mostly in the field of oxide electronics, oxide-based (nano) devices and oxide thin films deposition. In 2009, he focused on the fabrication of free-standing micro/nanostructures entirely made with epitaxial transition metal oxides thin films for the realization of prototypes of oxide-based MEMS/NEMS such as strain devices, multiresistive memories, programmable micromechanical resonators, microactuators and recently magnetic field detectors. He is coordinator of the H2020 FET-Open project OXiNEMS (www.oxinems.eu) aiming at developing high-sensitivity magnetic field detectors for biomagnetism using oxide-based NEMS. He is author/coauthor of more than 60 publications and 4 patents.

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