Thin-Film Electrodes Based on Two-Dimensional Nanomaterials for Neural Interfaces

Abstract

Detection and monitoring of neural signals is a fastadvancing area of research expected to impact a broad range of advanced applications, from healthcare to brain−machine and even brain-to-brain communications. Two-dimensional (2D) layered materials, such as graphene, MXenes, and transition metal dichalcogenides, could lead to the development of superior and ultrathin thin-film electrodes for neural interfaces thanks to their atomic thickness, high-conductivity properties, and potential to combine additional functionalities. This review focuses on the recent advancement of 2D materials-based thin-film sensors for monitoring of bio-physiological signals using invasive and noninvasive approaches.

Noninvasive Sensors for Brain–Machine Interfaces Based on Micropatterned Epitaxial Graphene

“…These parameters appear, hence, crucial for signal acquisition. The elastic band pressure is not necessarily transferred uniformly on all areas of the head because it also depends on the local curvature and hair distribution. , For comparisons, an equivalent eight-channel unpatterned sensor system was also tested, and it was confirmed that the HPEG sensors show better performance than the FEG sensors on the occipital region.…”

“…Nanometer-thick two-dimensional nanomaterials, especially graphene and graphene derivatives, are promising electrode materials for dry BMI sensors. , Their very thin nature, combined with high electrical conductivity, biocompatibility, corrosion resistance, and stability in sweat, are all very attractive characteristics for use as sensors for both invasive and noninvasive neural interfaces. − However, most of the reported noninvasive sensors based on two-dimensional materials typically consist of thin-film electrodes with a flat surface (such as tattoo sensors, e-skin, and e-textrodes) and are not compatible with application on hairy areas of the scalp. ,− In order to measure the EEG signals from the occipital region of the head, which corresponds to the visual cortex and is thus key for BMIs that rely on visual stimuli, the sensors need to be placed on the back of the head, typically covered by hair. As a reference, a typical human hair diameter is around 80 ± 10 μm, and the density is around 160 ± 10 hairs/cm 2 .…”

“…Nanometer-thick two-dimensional nanomaterials, especially graphene and graphene derivatives, are promising electrode materials for dry BMI sensors. 19,20 Their very thin nature, combined with high electrical conductivity, biocompatibility, corrosion resistance, and stability in sweat, are all very attractive characteristics for use as sensors for both invasive and noninvasive neural interfaces. 21−25 However, most of the reported noninvasive sensors based on two-dimensional materials typically consist of thin-film electrodes with a flat surface (such as tattoo sensors, e-skin, and e-textrodes) and are not compatible with application on hairy areas of the scalp.…”

ACS Applied Nano Materials Australia Forum

“…The three review articles in this forum are focused on the timely topics of (1) nanosized piezoelectric materials by Wang et al in a collaboration between the University of Melbourne and RMIT, (2) harvesting electrical energy from ambient moisture by Feng et al from the University of New South Wales (UNSW), and (3) recent advances in 2D-based electrodes for monitoring biophysiological signals, by Faisal and Iacopi from the University Technology Sydney …”

“…15 The three review articles in this forum are focused on the timely topics of (1) nanosized piezoelectric materials by Wang et al in a collaboration between the University of Melbourne and RMIT, 16 (2) harvesting electrical energy from ambient moisture by Feng et al from the University of New South Wales (UNSW), 17 and (3) recent advances in 2D-based electrodes for monitoring biophysiological signals, by Faisal and Iacopi from the University Technology Sydney. 18 Considering the high quality of the articles and reviews, we hope that the collected works in the Australia Forum appeal to the broad readership of ACS Applied Nano Materials. We are sincerely grateful to the authors from across Australia for their thoughtful and motivational contributions to this forum.…”