Carbon Nanotube Array‐Based Flexible Multifunctional Electrodes to Record Electrophysiology and Ions on the Cerebral Cortex in Real Time

Abstract

Electrophysiology and neurochemicals such as Ca2+, K+, and Na+ on the cerebral cortex can synergistically reflect the neurophysiological states. Transparent electrodes have been reported to record electrocorticography (ECoG) and image Ca2+ on the cerebral cortex surface. However, Ca2+ imaging is unable to track extracellular changes correlated with neural activities such as anesthesia, and imaging techniques to monitor K+ and Na+ are yet unavailable. Here, a flexible multifunctional electrode (FME) based on carbon nanotube array is presented to record ECoG and extracellular ions of Ca2+, K+, and Na+. The FME exhibits both lower impedance and higher capacitance than that of conventional gold electrodes. It simultaneously shows stable ion‐sensing performance and long‐term biocompatibility. The FME realizes multi‐model recording of ECoG and extracellular ions on the cerebral cortex surface of rats, providing an effective detection method for brain science.

Kirigami‐Structured, Low‐Impedance, and Skin‐Conformal Electronics for Long‐Term Biopotential Monitoring and Human–Machine Interfaces

“…These improved electrochemical performance confirms the superiority of the layer‐structured PEDOT:PSS/PVA/Ag NWs film in reducing the impedance and improving the charge storage capacity, which is strongly demanded for epidermal electrodes to record or deliver biopotential signals. [ 17 ] Furthermore, ensuring the safety and biocompatibility of epidermal electrodes is crucial for intimate contact with the skin. This was confirmed through a live/dead assay conducted on NIH 3T3 fibroblasts cultured on a PEDOT:PSS/PVA/Ag NWs film, along with a blank control group (Figure 2h,i).…”

“…[8] However, metal-based electrodes suffer from high interfacial impedance due to the mismatch between ionic and electronic currents during the coupling process and their low charge density. [17] As a promising alternative, poly (3,4-ethyllenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) is a commercially available conductive polymer with tunable rheological behavior, tunable electrical performance, and bio-compatibility. [4,18,19] Chemical vapor deposition-grown graphene covered with PEDOT:PSS layer has been utilized to create an ultra-conformal dry electrode for longterm electrophysiological signal recording with minimal motion artifacts.…”

Bi-directional electrical recording and stimulation of the intact retina

“…CNT microelectrodes on soft support will typically have similar specific capacitance (in the range of 1-2 mF/cm 2 ). A recently [28] presented ECoG probe using CNTs on PDMS electrodes exhibits specific capacitance of 1.5 mF/cm 2 , low impedance values of approximately 30 kΩ at 1 kHz and charge storage capacity of 0.35 mC/cm 2 . As a reference, Faradaic silver nanoparticles/PEDOT:PSS (Poly (3,4-ethylenedioxythiophene) Polystyrene Sulfonate) electrodes on polyimide can reach very low impedance value of 200 Ω (at 1 kHz) , exhibit capacitance of 0.4-60.6 mF/cm 2 and charge storage capacity of 1.083 -2.8 C/cm 2 by increasing PEDOT:PSS coating from 1 to 10 layers [29].…”

Challenges and Opportunities of Implantable Neural Interfaces: From Material, Electrochemical and Biological Perspectives

“…[135,142] Though CNT remained a potential biotoxicity, biocompatibility can be improved by chemical modification. [169] Yang et al [170] fabricated a flexible multifunctional electrode (FME) based on a CNT array, showing both lower impedance and higher CSC c (2.66 times) than that of conventional Au electrodes. Stable impedances can be observed after 10 000 bending cycles and 1000 stretching cycles.…”