Wearable electronics is a rapidly growing field that recently started to introduce successful commercial products into the consumer electronics market. Employment of biopotential signals in wearable systems as either biofeedbacks or control commands are expected to revolutionize many technologies including point of care health monitoring systems, rehabilitation devices, human–computer/machine interfaces (HCI/HMIs), and brain–computer interfaces (BCIs). Since electrodes are regarded as a decisive part of such products, they have been studied for almost a decade now, resulting in the emergence of textile electrodes. This study presents a systematic review of wearable textile electrodes in physiological signal monitoring, with discussions on the manufacturing of conductive textiles, metrics to assess their performance as electrodes, and an investigation of their application in the acquisition of critical biopotential signals for routine monitoring, assessment, and exploitation of cardiac (electrocardiography, ECG), neural (electroencephalography, EEG), muscular (electromyography, EMG), and ocular (electrooculography, EOG) functions.

Ear-centered physiological recordings offer rich amount of information originated by neural and cardiac activities. This paper investigates possible applications of graphene-based textiles for behind-the-ear discreet and unobtrusive electrocardiography (ECG) monitoring. We systematically analyzed the most suitable electrode positioning for wearable ear ECG and identified the mastoid area behind the ear helix to be suitable for cardiac monitoring, where the collected signals had a mean signal-to-noise ratio (SNR) of 29.87 dB. Later, graphene textiles were positioned on the selected locations, and we assessed the feasibility of a wearable headphone design for ear ECG through synchronous recording alongside conventional lead-I placement. We anticipate that contributions here are directly applicable to the extraction of heartrate, heart rate variability (HRV), and other cardiac P-QRS-T parameters for remote health monitoring as well as applications requiring vital signs for real-time stress or anxiety classification such as virtual reality headsets.

In this study, we report the use of graphene-coated fabrics as textile electrodes in surface electromyography (sEMG) acquisition. Their performance was compared with that of wet silver/silver chloride (Ag/AgCl) electrodes for the signals that were taken from three different muscle groups. Comparisons were performed in terms of the skin-electrode impedance (SEI), signal-to-noise ratio (SNR) and cross correlation. SEI values of graphene textile electrodes ( $\sim 90\text{k}\Omega $ ) were found to be well within the range of commercial Ag/AgCl electrodes ( $\sim 50\text{k}\Omega $ ). At 2 kg load, SNR values of 19.23 dB from triceps brachii, 27.18 dB from biceps brachii, and 28.13 dB from quadriceps femoris muscles were obtained, respectively; which showed that performance of graphene textile electrodes in static settings is at minimum 94% of clinical signal quality both in terms of SNR and similarity of signal morphologies in terms of cross correlation. After benchmarking the electrode performance, a proof of concept fully textile elastic band and a mobile acquisition circuit were combined to further validate the feasibility of surface electromyography with wearable graphene textiles through a step counter application, where the implemented wearable graphene textile-based step counter achieved on average a success rate above 90% for varying speed levels and up to a maximum of ~98%. Results suggests that graphene textiles could be a viable alternative to gelled Ag/AgCl electrodes and can be used to develop wearable, smart garment applications.