Electrochemistry of Graphene Nanoplatelets Printed Electrodes for Cortical Direct Current Stimulation

Hydrogels and Carbon Nanotubes: Composite Electrode Materials for Long-Term Electrocardiography Monitoring

This paper presents methods for developing high-performance interface electrode materials designed to enhance signal collection efficacy during long-term (over 24 h) electrocardiography (ECG) monitoring. The electrode materials are fabricated by integrating commercial ECG liquid hydrogels with carbon nanotubes (CNTs), which are widely utilized in dry-electrode technologies and extensively discussed in the current scientific literature. The composite materials are either prepared by dispersing CNTs within the commercial liquid hydrogel matrix or by encasing the hydrogels in macroscopic CNT films. Both approaches ensure the optimal wetting of the epidermis via the hydrogels, while the CNTs reduce material impedance and stabilize the drying process. The resulting electrode materials maintain their softness, allowing for micro-conformal skin attachment, and are biocompatible. Empirical testing confirms that the ECG electrodes employing these hybrid hydrogels adhere to relevant standards for durations exceeding 24 h. These innovative hybrid solutions merge the benefits of both wet and dry ECG electrode technologies, potentially facilitating the extended monitoring of ECG signals and thus advancing the diagnosis and treatment of various cardiac conditions.

Carbon-Based Composites with Biodegradable Matrix for Flexible Paper Electronics

The authors explore the development of paper-based electronics using carbon-based composites with a biodegradable matrix based on ethyl cellulose and dibasic ester solvent. The main focus is on screen-printing techniques for creating flexible, eco-friendly electronic devices. This research evaluates the printability with the rheological measurements, electrical properties, flexibility, and adhesion of these composites, considering various compositions, including graphene, graphite, and carbon black. The study finds that certain compositions offer sheet resistance below 1 kΩ/sq and good adhesion to paper substrates with just one layer of screen printing, demonstrating the potential for commercial applications, such as single-use electronics, flexible heaters, etc. The study also shows the impact of cyclic bending on the electrical parameters of the prepared layers. This research emphasizes the importance of the biodegradability of the matrix, contributing to the field of sustainable electronics. Overall, this study provides insights into developing environmentally friendly, flexible electronic components, highlighting the role of biodegradable materials in this evolving industry.

Edge-Functionalized Graphene/Polydimethylsiloxane Composite Films for Flexible Neural Cuff Electrodes

The design of neural electrodes has changed in the past decade, driven mainly by the development of new materials that open the possibility of manufacturing electrodes with adaptable mechanical properties and promising electrical properties. In this paper, we report on the mechanical and electrochemical properties of a polydimethylsiloxane (PDMS) composite with edge-functionalized graphene (EFG) and demonstrate its potential for use in neural implants with the fabrication of a novel neural cuff electrode. We have shown that a 200 μm thick 1:1 EFG/PDMS composite film has a stretchability of up to 20%, a Young's modulus of 2.52 MPa, and a lifetime of more than 10000 mechanical cycles, making it highly suitable for interfacing with soft tissue. Electrochemical characterization of the EFG/PDMS composite film showed that the capacitance of the composite increased up to 35 times after electrochemical reduction, widening the electrochemical water window and remaining stable after soaking for 5 weeks in phosphate buffered saline. The electrochemically activated EFG/PDMS electrode had a 3 times increase in the charge injection capacity, which is more than double that of a commercial platinum-based neural cuff. Electrochemical and spectrochemical investigations supported the conclusion that this effect originated from the stable chemisorption of hydrogen on the graphene surface. The biocompatibility of the composite was confirmed with an in vitro cell culture study using mouse spinal cord cells. Finally, the potential of the EFG/PDMS composite was demonstrated with the fabrication of a novel neural cuff electrode, whose double-layered and open structured design increased the cuff stretchability up to 140%, well beyond that required for an operational neural cuff. In addition, the cuff design offers better integration with neural tissue and simpler nerve fiber installation and locking.

Investigation of Carbon-Based Composites for Elastic Heaters and Effects of Hot Pressing in Thermal Transfer Process on Thermal and Electrical Properties

Wearable electronics are new structures with a wide range of possible applications. This study aims to analyze the effects of hot pressing in thermal transfer of different carbon-based composites as a new application method of screen-printed electronics on textiles. Flexible heaters were screen-printed on polyethylene terephthalate PET foil with composites based on graphene, carbon black, and graphite with different wt.%, measured and then hot pressed to measure and analyze differences. Research showed that the hot pressing process in thermal transfer resulted in decreased electrical resistance, increased power, and higher maximal temperatures. Best results were achieved with composites based on 12 wt.% graphene with sheet resistance lowered by about 40% and increased power by about 110%. This study shows promise for thermal transfer and screen-printing combination as an alternative for creating flexible electronics on textiles.