A Novel Highly Durable Carbon/Silver/Silver Chloride Composite Electrode for High-Definition Transcranial Direct Current Stimulation

Abstract

High-definition transcranial direct current stimulation (HD-tDCS) is a promising non-invasive neuromodulation technique, which has been widely used in the clinical intervention and treatment of neurological or psychiatric disorders. Sintered Ag/AgCl electrode has become a preferred candidate for HD-tDCS, but its service life is very short, especially for long-term anodal stimulation. To address this issue, a novel highly durable conductive carbon/silver/silver chloride composite (C/Ag/AgCl) electrode was fabricated by a facile cold rolling method. The important parameters were systematically optimized, including the conductive enhancer, the particle size of Ag powder, the C:Ag:PTFE ratio, the saline concentration, and the active substance loading. The CNT/Ag/AgCl-721 electrode demonstrated excellent specific capacity and cycling performance. Both constant current anodal polarization and simulated tDCS measurement demonstrated that the service life of the CNT/Ag/AgCl-721 electrodes was 15-16 times of that of sintered Ag/AgCl electrodes. The much longer service life can be attributed to the formation of the three-dimensional interpenetrating conductive network with CNT doping, which can maintain a good conductivity and cycling performance even if excessive non-conductive AgCl is accumulated on the surface during long-term anodal stimulation. Considering their low cost, long service life, and good skin tolerance, the proposed CNT/Ag/AgCl electrodes have shown promising application prospects in HD-tDCS, especially for daily life scenarios.

Polyvinyl alcohol/polyacrylamide double-network hydrogel-based semi-dry electrodes for robust electroencephalography recording at hairy scalp for noninvasive brain–computer interfaces

“…The electrode cavity (b) is detachably connected to the upper cover (a) using a thread. The Ag/AgCl coating was formed by coating Ag/AgCl conductive ink onto the inner surface of the upper cover (a) and the electrode cavity (b), which was used as a sensing material owing to its good non-polarizable feature [49]. The tapered PVA/PAM DNHs can penetrate through thick hair and achieve reliable contact with the scalp, substantially reducing the electrodescalp impedance.…”

Modeling the Transient Behavior of Ionic Diodes with the Nernst–Planck–Poisson Equations

“…The electrode area can either be increased geometrically, or by using a porous structure similar to that of a microporous capacitive electrode. [48,49]…”

One-Pot Synthesis of a Robust Crosslinker-Free Thermo-Reversible Conducting Hydrogel Electrode for Epidermal Electronics

“…This mismatch often leads to skin irritation, electrode degradation, and sweat-induced failure, all of which hamper signal quality in the long term. 2,3 Furthermore, those electrodes have a finite shelf life 4 due to the gradual conversion of Ag to AgCl over time, even during storage, severely impacting the stability and reliability of the electrodes.…”

“…Commercial electrophysiology devices are typically metal electrodes such as silver/silver chloride (Ag/AgCl) that, although highly conductive, are flat and rigid and hence do not adequately conform to human skin. This mismatch often leads to skin irritation, electrode degradation, and sweat-induced failure, all of which hamper signal quality in the long term. , Furthermore, those electrodes have a finite shelf life due to the gradual conversion of Ag to AgCl over time, even during storage, severely impacting the stability and reliability of the electrodes.…”