Signal Quality of Novel MXene-based "MXtrode" Dry Electrodes and Comparison to Gelled Ag/AgCl Electrodes
Creators: name: Rich, Ryan
Publisher: name: Open Science Framework
Year: 2022
Subjects: subject: Nanoscience and Nanotechnology
subject: Life Sciences
subject: Nanotechnology Fabrication
subject: Engineering
subject: Psychology
subject: FOS: Psychology
subject: Social and Behavioral Sciences
subject: Biomedical Engineering and Bioengineering
subject: Biotechnology
subject: Cognitive Psychology
subject: Neuroscience and Neurobiology
subject: Electrical and Computer Engineering
subject: Dry Electrode
subject: EEG
subject: MXene
subject: Novel Electrode

description: The necessity of using conductive gel has long limited the practicality of EEG since gelled systems require skilled preparation, experience signal degradation as the gel dries, and leave an uncomfortable residue in the hair that must be washed out. Recently, novel dry EEG electrodes have been developed by infusing MXenes, a family of highly conductive transition metal carbides, carbonitrides, and nitrides, into fibrous materials. A previous account reported high qualitative similarity between these dry MXene-based electrodes (MXtrodes) and gelled Ag/AgCl EEG signals and detected behaviorally-relevant neural responses on MXtrodes (Driscoll et al., 2021). A dry electrode with performance equal to gelled Ag/AgCl electrodes would be of great significance to the many clinical and basic research fields that utilize EEG and could make new domains of EEG research and applications practical. Previous efforts to develop dry electrode systems have been only partially successful because most existing dry electrode systems require uncomfortably high scalp pressure to reduce impedance, use large electrode sizes, and are more susceptible to artifact than gelled systems. These limitations may stem from the fundamental material limitations of Ag/AgCl, which is still the dominant skin-contact conductor in the most popular dry electrode systems. Alternative dry electrodes based on graphene and other materials have failed to gain practical adoption for various reasons, including insufficient signal quality, the difficulty of manufacturing, low biocompatibility, the complexity of preparation, discomfort, and fragility. The properties of dry MXtrodes address these weaknesses. MXtrodes are pliable and highly comfortable against the skin and do not require high contact pressure or extensive skin preparation. MXtrodes are safe and inexpensive to manufacture and have outstanding biocompatibility. MXtrodes also have significant advantages that go beyond addressing weaknesses in prior systems. Mxtrode arrays can be fabricated with at least 4x the theoretical maximum density of standard gelled disc electrodes, potentially greatly increasing resolution and redundancy. MXtrodes also have extremely low magnetic susceptibility and produce less MR artifact than standard MR-compatible platinum electrodes (Driscoll et al., 2021). Due to these advantages, quantitatively establishing that dry MXtrodes record EEG of similar quality to gelled Ag/AgCl electrodes common in clinical and research applications would be of high value. In order to do so, we will compare MXtrodes to Ag/AgCl electrodes in human subjects through a variety of metrics. We recorded long durations (&lt;1hr) of simultaneous dry MXtrode and gelled Ag/AgCl EEG using bifrontal 16ch MXtrode arrays. We will compare Ag/AgCl and Mxtrode signal characteristics in the domains of skin contact (impedance) and signal similarity (EEG time-series and spectral correlation).