Carbon Nanotube Fibers for Neural Recording and Stimulation

Abstract

Recordings and stimulations of neuronal electrical activity are topics of great interest in neuroscience. Many recording techniques, and even treatment of neurological disorders, can benefit from a microelectrode that is flexible, chemically inert, and electrically conducting and preferentially transfers electrons via capacitive charge injection. Commercial electrodes that currently exist and other electrodes that are being tested with the purpose of facilitating and improving the electron transport between solid materials and biological tissues still have some limitations. This paper discusses carbon nanotube (CNT)-based microelectrodes to record and stimulate neurons and compares their electron transport capabilities to noble metals such as Au and Ag. The recording ability of electrodes is tested through electroretinography on Sarcophaga bullata fly eyes by using Au and Ag wires and CNT fibers as electrodes. Stimulation is demonstrated through the implantation of Au wire and CNT fibers into the antennas of the Madagascar hissing cockroach (Gromphadorhina portentosa) to control their locomotion. Our results demonstrate that a particular property of the CNT fiber is its high rate of electron transfer, leading to an order of magnitude lower impedance compared to Au and Ag and an impressive 15.09 charge injection capacity. We also established that this carbon nanomaterial assembly performs well for in vivo electrophysiology, rendering it a promising prospect for neurophysiological applications.

Biomedical Applications of Carbon Nanomaterials: Fullerenes, Quantum Dots, Nanotubes, Nanofibers, and Graphene

“…The conductivity and nanoscale of CNMs are ideal for this and development is well underway to take advantage of them for these purposes. Groups such as Alvarez et al have been demonstrating the remarkable application of these electrodes in a variety of species, with exciting results [111]. Improved surface protection and biocompatibility performance in in vitro studies on MG-63 human osteoblast cells.…”

Electrode Materials for Chronic Electrical Microstimulation

“…For example, single CFEs with paryelne C insulation and PEDOT:PSS recording site, have been used as subcellular‐scale probes for electrophysiological recordings, demonstrating promising results in chronic in vivo recordings. [ 193 ] Furthermore, these microinvasive probes provided stable monitoring of subsecond evoked DA fluctuations in rats for over a year [ 200 ] and in nonhuman primates for over 100 days. [ 196 ] However, due to the smooth surface of the carbon fiber, CFEs require low impedance coating such as PEDOT:PSS, [ 193 ] PEDOT/pTS, [ 199 ] or electrodeposited Pt/Ir [ 199 ] to enable high SNR recordings and their CIL is insufficient for stimulation (0.05 mC cm −2 ).…”

“…Further, the dry spun CNT fibers can be assembled at up to 16 m s −1 linear speed, offering great potential for mass production. The proof of concept dry‐spun CNT fiber arrays (CIL: 15.09 mC cm −2 ) for neural stimulation in Madagascar hissing cockroach has been demonstrated recently, [ 200 ] motivating future testing for long‐term stimulation performance in higher order animal models.…”

Applications of Carbon Nanotubes in the Internet of Things Era

“…Compared with commercial Pt/Ir electrode, the CNT fiber as a brain-machine interface [91] decreases its diameter to 5 nm with advantages of easy repositioning and long duration detection. Moreover, CNT fiber has been employed in the recordings and stimulations of neuronal electrical activity [92]. Close electrode-tissue contact with excellent electrical fidelity has been created with a composite of carbon nanotubes and poly(3,4-ethylenedioxythiophene) (PEDOT) as a thin interface layer [93].…”