Wearable Neural Sensors Based on Epitaxial Graphene on 3C-SiC on Silicon

Recent advances in Neuroscience and Artificial Intelligence, particularly in paradigms and related algorithms for evoking and decoding intent from “brain waves”, ie the low-frequency, collective oscillations of millions of brain neurons, have paved the path to the use of electroencephalography (EEG) as a non-invasive platform for brain-computer interface (BCI) [1]. Although the spatial-temporal resolution of EEG is inferior to the use of implanted interfaces, the wearable nature of such BCI is of great importance for most of the large -scale uses that do not involve mitigating severe disabilities.<br/>However, one of the main bottlenecks for EEG -based BCIs is now the availability of suitable dry sensors. Dry sensors tend to show a relatively high contact impedance with the skin, which hampers an accurate read-out of the ~μV amplitude biopotential signals to be read at scalp locations, because of their strong capacitive component in the contact [2]. In addition, their contact with the skin needs to be stable during movement and reliable over long-term usage outside lab settings, which is another key challenge due to corrosion, biocompatibility and slipping issues. The use of 2D materials for neural sensors open new promising possibilities in this application area [3].<br/>We have pioneered the use of epitaxial graphene on silicon carbide on silicon as a low- contact impedance EEG sensor which is extremely reliable upon long-term usage [4]. The produced sensors are wafer- thin, biocompatible with the skin, and show a lower contact impedance as compared to bulkier commercial sensors. In particular, we observe that their contact impedance improves once in contact with the skin, thanks to a gradual wetting of the graphene’s surface [4]. In addition, we show that the sensors are remarkably resilient to corrosion as they do not delaminate and show minimal reduction of performance upon storage in a highly saline environment for up to one year. In this contribution, we will share the latest progress in the use of epitaxial graphene sensors mounted on a head helmet for the hands-free control of a remote robotic platform.<br/>[1] F Iacopi and CT Lin, A perspective on electroencephalography sensors for brain-computer interfaces, , accepted in Prog.Biomed.Eng. https://doi.org/10.1088/2516-1091/ac993d.<br/>[2] G Lia, S Wang, YY Duan, Sensors & Actuators: B. Chemical 277, 250–260, 2018.<br/>[3] SN Faisal, F Iacopi, ACS Applied Nano Materials 5 (8), 10137-10150, 2022.<br/>[4] SN Faisal, M Amjadipour, K Izzo, JA Singer, A Bendavid, CT Lin, F Iacopi<br/>Journal of Neural Engineering 18 (6), 066035, 2021.