Characterization of the electrode-skin impedance of textile electrodes

Abstract

Wearable systems are expected to contribute for improving traditional biopotential signals monitoring devices due to higher freedom and unobtrusiveness provided to the wearer. Textile electrodes present advantages compared with the conventional Ag/AgCl electrodes for the capturing of biopotentials, namely in terms of skin irritation due to the hydrogel and the need of a technician to place the electrodes on the correct positions. Due to the lack of hydrogel, textile electrodes present different electrical contact characteristics. The skinelectrode impedance is an important feature since it affects the captured signal quality. Although a low impedance is desired, a comfortable wearable system should not require the electrodes to be covered by the hydrogel or be moistened. A forearm sleeve provided with textile electrodes was used to study the electrode-skin impedance and the signal-to-noise ratio (SNR) of surface electromyographic (EMG) signals on a long-term use basis. The sleeve can be adjusted for different levels of tightening to control the pressure applied on the electrodes. The obtained results provide valuable information on the pressure that the textile garments of a sleeve or vest should apply on the recording electrodes, in order to assure a good electrical and mechanical contact between the electrodes and the skin and decrease the noise due to motion. It was observed that the electrode-skin impedance measurement alone is not sufficient to establish a relation with the SNR. The extraction of parameters from an electrical equivalent model of the electrode-skin interface allows to determine a relation with the model parameters and the SNR. The evaluation of these parameters during long-term monitoring will allow assessing the quality of biopotential measurements in textile electrodes.

Ferromagnetic, Folded Electrode Composite as a Soft Interface to the Skin for Long‐Term Electrophysiological Recording

“…As in figure 4a, the electrodes lie between the electrical lead-out (or thin magnet bonded on contact pad) and the skin (or epidermis). The associated model is in figure 4b [35, 36]. Here, the voltage source E hc corresponds to the half cell potential, the capacitance C d indicates the electrical charge accumulated between the electrode and the skin, R d is the resistance between the electrode and the skin during the charge transfer, and R s is related to the sweat and the underlying skin tissue, such as epidermis, dermis, and subcutaneous layers.…”

“…However, R s , alone itself, cannot be an independent current path. In this study, we chose the equivalent circuit model from reference [35]. This model is the most simplified version to describe electrochemical impedance of the electrode in electrolyte.…”

Systematic review of textile-based electrodes for long-term and continuous surface electromyography recording

“…Textiles as support materials -'add on' Mechanical attachment (often inorganic) Sleeves 38,39 Taping Socks 63 Temporary fixture (often for testing) Electrodes fixed by elastic band 59,65 Cut and sew Jogging 68,[72][73][74] Armband/sleeves/elastic band [47][48][49]56,57,61,64,67,70,76,77,79 Integrated onto Coating Knitted fabric straps 55 Stencil printing Armband/sleeves 58,60 Integrated into Embroidery/sewing Jogging Figure 6. Wearable system integration levels.…”

Adaptive analogue calibration technique to compensate electrode motion artefacts in biopotential recording

“…At low frequency [e.g. electrocardiogram (ECG) 0.05–150 Hz [17]], the resistive components of the electrodes are dominant [18, 19] and therefore are represented as resistors and . The common mode EMI () is coupled to the human body through the electrodes.…”