scholarly journals Textile Electrodes: Influence of Knitting Construction and Pressure on the Contact Impedance

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1578
Author(s):  
Luisa Euler ◽  
Li Guo ◽  
Nils-Krister Persson
Keyword(s):  
Smooth Surface ◽  
Research Field ◽  
Uneven Surface ◽  
Contact Impedance ◽  
Dry Electrodes ◽  
Textile Electrodes ◽  
Human Forearm ◽  
Wet Condition ◽  
Electrode Contact ◽  
Influencing Parameters

Textile electrodes, also called textrodes, for biosignal monitoring as well as electrostimulation are central for the emerging research field of smart textiles. However, so far, only the general suitability of textrodes for those areas was investigated, while the influencing parameters on the contact impedance related to the electrode construction and external factors remain rather unknown. Therefore, in this work, six different knitted electrodes, applied both wet and dry, were compared regarding the influence of specific knitting construction parameters on the three-electrode contact impedance measured on a human forearm. Additionally, the influence of applying pressure was investigated in a two-electrode setup using a water-based agar dummy. Further, simulation of an equivalent circuit was used for quantitative evaluation. Indications were found that the preferred electrode construction to achieve the lowest contact impedance includes a square shaped electrode, knitted with a high yarn density and, in the case of dry electrodes, an uneven surface topography consisting of loops, while in wet condition a smooth surface is favorable. Wet electrodes are showing a greatly reduced contact impedance and are therefore to be preferred over dry ones; however, opportunities are seen for improving the electrode performance of dry electrodes by applying pressure to the system, thereby avoiding disadvantages of wet electrodes with fluid administration, drying-out of the electrolyte, and discomfort arising from a “wet feeling”.

scholarly journals Dedicated Algorithm for Unobtrusive Fetal Heart Rate Monitoring Using Multiple Dry Electrodes

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4298
Author(s):  
Alessandra Galli ◽  
Elisabetta Peri ◽  
Yijing Zhang ◽  
Rik Vullings ◽  
Myrthe van der Ven ◽  
...  
Keyword(s):  
Heart Rate ◽  
Fetal Heart Rate ◽  
Fetal Heart ◽  
Processing System ◽  
Motion Artifacts ◽  
Accurate Estimation ◽  
Fetal Heart Rate Monitoring ◽  
Dry Electrodes ◽  
Textile Electrodes ◽  
Dry Electrode

Multi-channel measurements from the maternal abdomen acquired by means of dry electrodes can be employed to promote long-term monitoring of fetal heart rate (fHR). The signals acquired with this type of electrode have a lower signal-to-noise ratio and different artifacts compared to signals acquired with conventional wet electrodes. Therefore, starting from the benchmark algorithm with the best performance for fHR estimation proposed by Varanini et al., we propose a new method specifically designed to remove artifacts typical of dry-electrode recordings. To test the algorithm, experimental textile electrodes were employed that produce artifacts typical of dry and capacitive electrodes. The proposed solution is based on a hybrid (hardware and software) pre-processing step designed specifically to remove the disturbing component typical of signals acquired with these electrodes (triboelectricity artifacts and amplitude modulations). The following main processing steps consist of the removal of the maternal ECG by blind source separation, the enhancement of the fetal ECG and identification of the fetal QRS complexes. Main processing is designed to be robust to the high-amplitude motion artifacts that corrupt the acquisition. The obtained denoising system was compared with the benchmark algorithm both on semi-simulated and on real data. The performance, quantified by means of sensitivity, F1-score and root-mean-square error metrics, outperforms the performance obtained with the original method available in the literature. This result proves that the design of a dedicated processing system based on the signal characteristics is necessary for reliable and accurate estimation of the fHR using dry, textile electrodes.

scholarly journals Electrochemical Characteristics Based on Skin-Electrode Contact Pressure for Dry Biomedical Electrodes and the Application to Wearable ECG Signal Acquisition

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jinzhong Song ◽  
Tianshu Zhou ◽  
Zhonggang Liang ◽  
Ruoxi Liu ◽  
Jianping Guo ◽  
...  
Keyword(s):  
Contact Pressure ◽  
Electrode Pair ◽  
Electrochemical Characteristics ◽  
Polarization Voltage ◽  
Skin Electrode ◽  
Textile Electrodes ◽  
Biomedical Electrodes ◽  
Electrode Contact ◽  
Evaluation Platform ◽  
Electrochemical Evaluation

Based on one simulated skin-electrode electrochemical interface, some electrochemical characteristics based on skin-electrode contact pressure (SECP) for dry biomedical electrodes were analysed and applied in this research. First, 14 electrochemical characteristics including 2 static impedance (SI) characteristics, 11 alternating current impedance (ACI) characteristics and one polarization voltage (PV), and 4 SECP characteristics were extracted in one electrochemical evaluation platform, and their correlation trends were statistically analysed. Second, dry biomedical electrode samples developed by the company and the laboratory, including textile electrodes, Apple watch, AMAZFIT rice health bracelet 1S, and stainless steel electrodes, were placed horizontally and vertically on the “skin” surface of the electrochemical evaluation platform, whose polarization voltages were quantitatively analysed. Third, electrocardiogram (ECG) collection circuits based on an impedance transformation (IT) circuit for textile electrodes were designed, and a wearable ECG acquisition device was designed, which could obtain complete ECG signals. Experimental results showed SECP characteristics for dry electrodes had good correlations with static impedance and ACI characteristics and the better correlation values among 2-10 Hz. In addition, polarization voltages in vertical state were smaller in horizontal state for dry biomedical electrodes, and polarization voltage of electrode pair (PVEP) values for Apple watch bottom was always smaller than ones for Apple watch crown and LMF-2 textile electrode. And the skin-electrode contact impedance of IT textile electrodes was less than the traditional textile electrodes.

Study on the Measurement Method of Skin Textile Electrodes Contact Impedance

2018 ◽  
Vol s5 ◽  
Author(s):  
Amale Ankhili ◽  
Xuyuan Tao ◽  
Cedric Cochrane ◽  
David Coulon ◽  
Vladan Koncar
Keyword(s):  
Measurement Method ◽  
Contact Impedance ◽  
Textile Electrodes

scholarly journals Development of a Smart Helmet for Strategical BCI Applications

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1867 ◽  
Author(s):  
Li-Wei Ko ◽  
Yang Chang ◽  
Pei-Lun Wu ◽  
Heng-An Tzou ◽  
Sheng-Fu Chen ◽  
...  
Keyword(s):  
Data Collection ◽  
Signal To Noise Ratio ◽  
The Novel ◽  
Contact Impedance ◽  
Practical Applications ◽  
Dry Electrodes ◽  
Average Accuracy ◽  
Eeg Data ◽  
Electrophysiological Measurements ◽  
User Acceptability

Conducting electrophysiological measurements from human brain function provides a medium for sending commands and messages to the external world, as known as a brain–computer interface (BCI). In this study, we proposed a smart helmet which integrated the novel hygroscopic sponge electrodes and a combat helmet for BCI applications; with the smart helmet, soldiers can carry out extra tasks according to their intentions, i.e., through BCI techniques. There are several existing BCI methods which are distinct from each other; however, mutual issues exist regarding comfort and user acceptability when utilizing such BCI techniques in practical applications; one of the main challenges is the trade-off between using wet and dry electroencephalographic (EEG) electrodes. Recently, several dry EEG electrodes without the necessity of conductive gel have been developed for EEG data collection. Although the gel was claimed to be unnecessary, high contact impedance and low signal-to-noise ratio of dry EEG electrodes have turned out to be the main limitations. In this study, a smart helmet with novel hygroscopic sponge electrodes is developed and investigated for long-term usage of EEG data collection. The existing electrodes and EEG equipment regarding BCI applications were adopted to examine the proposed electrode. In the impedance test of a variety of electrodes, the sponge electrode showed performance averaging 118 kΩ, which was comparable with the best one among existing dry electrodes, which averaged 123 kΩ. The signals acquired from the sponge electrodes and the classic wet electrodes were analyzed with correlation analysis to study the effectiveness. The results indicated that the signals were similar to each other with an average correlation of 90.03% and 82.56% in two-second and ten-second temporal resolutions, respectively, and 97.18% in frequency responses. Furthermore, by applying the proposed differentiable power algorithm to the system, the average accuracy of 21 subjects can reach 91.11% in the steady-state visually evoked potential (SSVEP)-based BCI application regarding a simulated military mission. To sum up, the smart helmet is capable of assisting the soldiers to execute instructions with SSVEP-based BCI when their hands are not available and is a reliable piece of equipment for strategical applications.

scholarly journals 3D Printable Dry EEG Electrodes with Coiled-Spring Prongs

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4733
Author(s):  
Masaya Kimura ◽  
Shintaro Nakatani ◽  
Shin-Ichiro Nishida ◽  
Daiju Taketoshi ◽  
Nozomu Araki
Keyword(s):  
Mechanical Properties ◽  
Spring Constant ◽  
Contact Model ◽  
3D Printer ◽  
Contact Impedance ◽  
Dry Electrodes ◽  
Coiled Spring ◽  
Alpha Waves

Various dry electroencephalography (EEG) electrodes have been developed. Dry EEG electrodes need to be pressed onto the scalp; therefore, there is a tradeoff between keeping the contact impedance low and maintaining comfort. We propose an approach to solve this tradeoff through the printing of complex-shaped electrodes by using a stereolithography 3D printer. To show the feasibility of our approach, we fabricated electrodes that have flexible fingers (prongs) with springs. Although dry electrodes with flexible prongs have been proposed, a suitable spring constant has not been obtained. In this study, the spring constant of our electrodes was determined from a contact model between the electrodes and the scalp. The mechanical properties and reproductivity of the electrodes were found to be sufficient. Finally, we measured the alpha waves when a participant opened/closed his eyes by using our electrodes.

A comfortability and signal quality study of conductive weave electrodes in long-term collection of human electrocardiographs

2018 ◽  
Vol 89 (11) ◽  
pp. 2098-2112 ◽  
Author(s):  
Xueliang Xiao ◽  
Ke Dong ◽  
Chenhao Li ◽  
Guanzheng Wu ◽  
Hongtao Zhou ◽  
...  
Keyword(s):  
Skin Irritation ◽  
Woven Fabrics ◽  
Comfort Level ◽  
Signal Quality ◽  
High Quality ◽  
Contact Impedance ◽  
Ecg Signals ◽  
Skin Contact ◽  
Textile Electrodes

Long-term electrocardiogram (ECG) recording can reveal some vital cardiovascular disorders and provide warning of human sudden cerebral or vascular diseases in advance. This requires high-quality ECG skin electrodes. Gel (Ag/AgCl) electrodes were reported to have good signal quality in ECG acquisition, but easily caused human skin irritation or allergy. Consequently, textile electrodes have attracted more attention for long-term ECG acquisition. In this paper, eight woven fabrics with diverse yarns and weft densities were fabricated in plain and honeycomb structures. The fabrics were investigated in terms of comfortability, fabric–skin contact impedance and acquired bio-signal quality. Honeycomb weave electrodes were measured with a high comfort level from subjective and objective views, including pleasant tactile comfort, high visual acceptance, good air permeability and good heat transfer. Weave electrodes made of all conductive filaments in high density had low skin contact impedance and high-quality ECG signals. An increase of compression load on weave electrodes resulted in a decrease of contact impedance with a high signal quality. A conductive honeycomb weave with unit repeat of 6*6 warps*wefts presented the highest score of acquired ECG signals of all studied electrodes based on the qualities of the QRS complex, P and T waves, R peak amplitude and variation and signal-to-noise ratio. This study contributes to the future design and fabrication of textile electrodes using honeycomb weave in long-term and real-time collection of human ECGs.

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