Flexible PDMS Composite Electrodes with Boronic Acid-Modified Carbon Dots for Surface Electrophysiological Signal Recording

Abstract

Conventional surface electrodes are composed of rigid metals such as Ag/AgCl that are not only harsh to the skin but also irritating if used as wet electrodes. Furthermore, rigid, inflexible surface electrodes can cause patient discomfort when used for the long term. To reduce the mechanical mismatch, flexible alternatives to metal electrodes are needed. This study reports the development of highly flexible composite electrodes fabricated from the conductive dopant boronic acid-modified carbon dots embedded in a polydimethylsiloxane matrix. The electrodes were characterized for their structural, electrochemical, and mechanical characteristics and for their ability to record electrophysiological signals. Furthermore, the composition of these electrodes was varied systematically to obtain the optimal electrochemical and mechanical properties. The best-performing electrode, composed of 10% boronic acid-modified carbon dots, 16% glycerol, and 74% polydimethylsiloxane (8:1 elastomer to curing agent), had a smooth surface, a promising conductivity of 9.62 × 10 −3 S/cm, an impedance of 964 kΩ at 1 kHz, and a charge storage capacity of 21.4 μC/cm 2 . This electrode had a Young's modulus of 0.0545 MPa, which is compatible with biological tissues' elasticity. The fabricated electrodes recorded high-quality electrocardiography signals with a promising signal-to-noise ratio (SNR) of 36.75 dB that is comparable to that of commercial Ag/AgCl, which had an SNR of 39.98 dB. A similarly good performance was observed with electromyography. Furthermore, the developed flexible surface electrodes maintained their ability to record highquality ECG and EMG over a period of 3 weeks.

2D Optimized Electrodes for Highly Sensitive and Biocompatible Neural Recording

“…One approach involves the use of nanomaterials, such as Pt black and CNT coatings, − which increase the surface active sites of the electrodes, lowering the interfacial impedance and thus enhancing the sensitivity of neural signal recording. − However, nanomaterials as electrode surface modifications may degrade over time and leave residues, posing risks in terms of biocompatibility and safety. The second type involves the modification with a conductive polymer, such as PEDOT, PPy, and PDMS, which reduce impedance and enhance charge injection capacity. − Additionally, these modifications allow for better adaptation to the surface of biological tissues during implantation, reducing damage to the tissues. − However, deformation of the electrodes during implantation can lead to performance degradation, and poor environmental conditions and long-term use may lead to layering and failure of the coating due to the high environmental stability requirements of conductive polymer materials . Therefore, there is a need to seek a neural interface that can simultaneously meet the requirements of a high signal-to-noise ratio and high biocompatibility.…”

MXene-Based Flexible Electrodes for Electrophysiological Monitoring

“…Both these studies utilized metal fillers, but other studies explored the possibility of compositing less harsh conductive polymers with PDMS. In a recent study, Ali et al created flexible PDMS composite electrodes featuring boronic acid-modified carbon dots for the recording of surface electrophysiological signals [ 18 ]. These electrodes exhibited a signal-to-noise ratio (SNR) of 36.75 dB, which is comparable to commercially available Ag/AgCl electrodes, along with a conductivity of 9.62 × 10 −3 S/cm.…”