Paper-Based Flexible Electrode Using Chemically-Modified Graphene and Functionalized Multiwalled Carbon Nanotube Composites for Electrophysiological Signal Sensing

Abstract

Flexible paper-based physiological sensor electrodes were developed using chemically-modified graphene (CG) and carboxylic-functionalized multiwalled carbon nanotube composites (f@MWCNTs). A solvothermal process with additional treatment was conducted to synthesize CG and f@MWCNTs to make CG-f@MWCNT composites. The composite was sonicated in an appropriate solvent to make a uniform suspension, and then it was drop cast on a nylon membrane in a vacuum filter. A number of batches (0%~35% f@MWCNTs) were prepared to investigate the performance of the physical characteristics. The 25% f@MWCNT-loaded composite showed the best adhesion on the paper substrate. The surface topography and chemical bonding of the proposed CG-f@MWCNT electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy, respectively. The average sheet resistance of the 25% CG-f@MWCNT electrode was determined to be 75 Ω/□, and it showed a skin contact impedance of 45.12 kΩ at 100 Hz. Electrocardiogram (ECG) signals were recorded from the chest and fingertips of healthy adults using the proposed electrodes. The CG-f@MWCNT electrodes demonstrated comfortability and a high sensitivity for electrocardiogram signal detection.

Challenges in Design and Fabrication of Flexible/Stretchable Carbon- and Textile-Based Wearable Sensors for Health Monitoring: A Critical Review

“…In addition, with the vacuum filtration process, carbon-based film having well-controlled configurational factors such as thickness, width, and length can contribute to manufacturing carbon-based wearable devices on paper substrates. Hossain et al reported a paper-based flexible dry-electrode for detecting electrocardiogram (ECG) signals by using a vacuum filtration method and a hybrid composite material composed of chemically modified graphene and carboxylic groups-functionalized short multi-walled carbon nanotubes (CG-f@MWCNTs), as shown in Figure 2 f [ 59 ]. However, this process is limited to those used for filter-paper substrates.…”

“…Drop-casting and vacuum filtration; ( e ) reduced graphene oxide (rGO) film deposition onto a functionalized polyethylene terephthalate (PET) substrate using drop-casting process (reproduced with permission [ 58 ] copyright 2014, Elsevier). ( f ) Paper-based hybrid chemically modified graphene and carboxylic groups-functionalized short multi-walled carbon nanotube-based dry electrode (CG-f@MWCNTs) for electrophysiological signal sensing (reproduced with permission [ 59 ] copyright 2019, MDPI AG).…”

Flexible Electronics for Monitoring in vivo Electrophysiology and Metabolite Signals

“…However, integrating conventional electrodes into the neural system of living animals is complicated by the differences in the mechanical properties of biological surfaces compared to glass or metal (Ganesana et al, 2019;Ji et al, 2019;Liu et al, 2019;Peng et al, 2019). As a result, the development of electrophysiological electrodes with appropriate mechanical (flexible and soft) properties, biocompatibility, and high electrical/electrochemical performance has become a promising field of research for monitoring and modulating neural interfaces with soft tissues, especially for implantation (Hong and Lieber, 2019;Hossain et al, 2019;Jayant et al, 2019;Das et al, 2020).…”

A Novel Wearable Flexible Dry Electrode Based on Cowhide for ECG Measurement

“…There are many kinds of substrate materials for flexible dry electrodes, such as carbon-based materials, artificial fabric [ 32 ], papers [ 33 ] and so on. However, natural leather material is rarely used as the substrate.…”