Conception, development and evaluation of polymer-based screen-printed textile electrodes for biopotential monitoring

Wearable technologies represent the new frontier of vital signs monitoring in different applications, from fitness to health. With the progressive miniaturization of the electronic components, enabling the implementation of portable and hand-held acquisition and recording devices, the research focus has shifted toward the development of effective and unobtrusive textile electrodes. This work deals with the study, development and characterization of organic-polymer-based electrodes for biopotentials. After an overview of the main materials and fabrication technologies presented so far in the scientific literature, the possibility to use these electrodes as an alternative to the Ag/AgCl disposable gelled electrodes usually adopted in clinical practice was tested. For this purpose, several textile electrode realization techniques were studied and optimized, in order to create electrodes with adequate features to detect two fundamental physiological signals: the electrocardiogram (ECG) and the electromyogram (EMG). The electrodes were obtained by depositing on the fabric the organic bio-compatible polymer poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) with three deposition procedures: dipcoating, ink-jet printing and screen printing. The physical\u2013chemical properties of the polymer solution were varied for each procedure to obtain an optimal and reproducible result. For what concerns the ECG signal, the research activity focused on screen-printed textile electrodes and their performance was first assessed by benchtop measurements and then by human trials. The first tests demonstrated that, by adding solid or liquid electrolytes the electrodes, the largest part of the characteristics required by the ANSI/AAMI EC12:2000 standard for gelled ECG electrodes can be achieved. Tests performed in different conditions showed that the skin contact impedance and the ECG morphological features are highly similar to those obtainable with disposable gelled Ag/AgCl electrodes (\u3c1 > 0.99). A trial with ten subjects revealed also the capability of the proposed electrodes to accurately capture with clinical instruments an ECG morphology with performance comparable to off-the-shelf disposable electrodes. Furthermore, the proposed textile electrodes preserve their electrical properties and functionality even after several mild washing cycles, while they suffered physical stretching. Similar tests were performed on screen-printed textile electrodes fabricated in two different sizes to test them as EMG sensors, with and without electrolytes. After a series of controlled acquisitions performed by electro-stimulating the muscles in order to analyze the waveform morphologu of the M-wave, the statistical analysis showed a high similarity in terms of rms of the noise and electrode-skin impedance between conventional and textile electrodes with the addition of solid hydrogel and saline solution. Furthermore, the M-wave recorded on the tibialis anterior muscle during the stimulation of the peroneal nerve was comparatively analyzed between conventional and textile electrodes. The comparison provided an R2 value higher than 97% in all measurement conditions. These results opened their use in smart garments for real application scenarios and for this purpose were developed a couple of smart shirts able to detect the EGC and the EMG signal. The results indicated that this approach could be adopted in the future for the development of smart garments able to comfortably detect physiological signals

Graphene textile smart clothing for wearable cardiac monitoring

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 reports on the synthesis and application of graphene nanotextiles for the development of wearable electrocardiography (ECG) sensors for personalized health monitoring applications. In this study, we show for the first time that the electrocardiogram was successfully obtained with graphene textiles placed on a single arm. The use of only one elastic armband, and an “all-textile-approach” facilitates seamless heart monitoring with maximum comfort to the wearer. The functionality of graphene textiles produced using dip coating and stencil printing techniques has been demonstrated by the non-invasive measurement of ECG signals, up to 98% excellent correlation with conventional pre-gelled, wet, silver/silver-chloride (Ag / AgCl) electrodes. Heart rate have been successfully determined with ECG signals obtained in different situations. The system-level integration and holistic design approach presented here will be effective for developing the latest technology in wearable heart monitoring devices

Validation of polymer-based screen-printed textile electrodes for surface EMG detection

In recent years, the variety of textile electrodes developed for electrophysiological signal detection has increased rapidly. Among the applications that could benefit from this advancement, those based on surface electromyography (sEMG) are particularly relevant in rehabilitation, training and muscle function assessment. In this work, we validate the performance of polymer-based screen-printed textile electrodes for sEMG signal detection. We obtained these electrodes by depositing poly-3,4-ethylenedioxythiophene doped with poly(styrene sulfonate) (PEDOT:PSS) onto cotton fabric, and then selectively changing the physical properties of the textile substrate. The manufacturing costs are low and this process meets the requirements of textile-industry production lines. The validation of these electrodes was based on their functional and electrical characteristics, assessed for two different electrode sizes and three skin-interface conditions (dry, solid hydrogel or saline solution), and compared to those of conventional disposable gelled electrodes. Results show high similarity in terms of noise amplitude and electrode-skin impedance between the conventional and textile electrodes with the addition of solid hydrogel or saline solution. Furthermore, we compared the shape of the electrically-induced sEMG, as detected by conventional and textile electrodes from tibialis anterior. The comparison yielded an R2 value higher than 97% for all measurement conditions. Preliminary tests in dynamic conditions (walking) revealed the exploitability of the proposed electrode technology with saline application for the monitoring of sEMG for up to 35 minutes of activity. These results suggest that the proposed screen-printed textile electrodes may be an effective alternative to the conventional gelled electrodes for sEMG acquisition, thereby providing new opportunities in clinical and wellness fields

Textile Concentric Ring Electrodes for ECG Recording Based on Screen-Printing Technology

[EN] Among many of the electrode designs used in electrocardiography (ECG), concentric ring electrodes (CREs) are one of the most promising due to their enhanced spatial resolution. Their development has undergone a great push due to their use in recent years; however, they are not yet widely used in clinical practice. CRE implementation in textiles will lead to a low cost, flexible, comfortable, and robust electrode capable of detecting high spatial resolution ECG signals. A textile CRE set has been designed and developed using screen-printing technology. This is a mature technology in the textile industry and, therefore, does not require heavy investments. Inks employed as conductive elements have been silver and a conducting polymer (poly (3,4-ethylenedioxythiophene) polystyrene sulfonate; PEDOT: PSS). Conducting polymers have biocompatibility advantages, they can be used with flexible substrates, and they are available for several printing technologies. CREs implemented with both inks have been compared by analyzing their electric features and their performance in detecting ECG signals. The results reveal that silver CREs present a higher average thickness and slightly lower skin-electrode impedance than PEDOT: PSS CREs. As for ECG recordings with subjects at rest, both CREs allowed the uptake of bipolar concentric ECG signals (BC-ECG) with signal-to-noise ratios similar to that of conventional ECG recordings. Regarding the saturation and alterations of ECGs captured with textile CREs caused by intentional subject movements, silver CREs presented a more stable response (fewer saturations and alterations) than those of PEDOT: PSS. Moreover, BC-ECG signals provided higher spatial resolution compared to conventional ECG. This improved spatial resolution was manifested in the identification of P1 and P2 waves of atrial activity in most of the BC-ECG signals. It can be concluded that textile silver CREs are more suitable than those of PEDOT: PSS for obtaining BC-ECG records. These developed textile electrodes bring the use of CREs closer to the clinical environment.Grant from the Ministerio de Economia y Competitividad y del Fondo Europeo de Desarrollo Regional. DPI2015-68397-R (MINECO/FEDER). This work was also supported by the Spanish Government/FEDER funds (grant number MAT2015-64139-C4-3-R (MINECO/FEDER)).Lidon-Roger, JV.; Prats-Boluda, G.; Ye Lin, Y.; Garcia Casado, FJ.; Garcia-Breijo, E. (2018). Textile Concentric Ring Electrodes for ECG Recording Based on Screen-Printing Technology. Sensors. 18(1):300-314. https://doi.org/10.3390/s18010300S30031418

Wearable smart textiles for long-term electrocardiography monitoring : a review

The continuous and long-term measurement and monitoring of physiological signals such as electrocardiography (ECG) are very important for the early detection and treatment of heart disorders at an early stage prior to a serious condition occurring. The increasing demand for the continuous monitoring of the ECG signal needs the rapid development of wearable electronic technology. During wearable ECG monitoring, the electrodes are the main components that affect the signal quality and comfort of the user. This review assesses the application of textile electrodes for ECG monitoring from the fundamentals to the latest developments and prospects for their future fate. The fabrication techniques of textile electrodes and their performance in terms of skin–electrode contact impedance, motion artifacts and signal quality are also reviewed and discussed. Textile electrodes can be fabricated by integrating thin metal fiber during the manufacturing stage of textile products or by coating textiles with conductive materials like metal inks, carbon mate-rials, or conductive polymers. The review also discusses how textile electrodes for ECG function via direct skin contact or via a non-contact capacitive coupling. Finally, the current intensive and promising research towards finding textile-based ECG electrodes with better comfort and signal quality in the fields of textile, material, medical and electrical engineering are presented as a perspective

Electrically Conductive Cotton Textile and Its Applications

Electronic textiles (e-textiles) have been considered as important applications in wearable electronics, which can combine the functionality of smart electronic devices with the comfort and flexibility of stylish clothing. Herein, we have successfully prepared a conductive textile via electroless deposition onto cotton textiles by using a three-step treatment process. The cotton textiles are first dipped in P4VP-SU8 solution to form a uniform layer for the subsequent absorption of silver ions. Then, the cotton textiles are immersed in silver nitrate solution in preparation for the next step electroless deposition. The sheet resistance can be as low as 0.05 Ωsq-1. Two sensors were made based on the copper coated cotton textiles. One is flexible pressure sensor, the other is ECG sensor. Both sensors performed well, proving this method is a promising candidate for applications in the fabrication of functional textile-based wearable devices

The status of textile-based dry EEG electrodes

Electroencephalogram (EEG) is the biopotential recording of electrical signals generated by brain activity. It is useful for monitoring sleep quality and alertness, clinical applications, diagnosis, and treatment of patients with epilepsy, disease of Parkinson and other neurological disorders, as well as continuous monitoring of tiredness/ alertness in the field. We provide a review of textile-based EEG. Most of the developed textile-based EEGs remain on shelves only as published research results due to a limitation of flexibility, stickability, and washability, although the respective authors of the works reported that signals were obtained comparable to standard EEG. In addition, nearly all published works were not quantitatively compared and contrasted with conventional wet electrodes to prove feasibility for the actual application. This scenario would probably continue to give a publication credit, but does not add to the growth of the specific field, unless otherwise new integration approaches and new conductive polymer composites are evolved to make the application of textile-based EEG happen for bio-potential monitoring

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

To demonstrate the wearable flexible/stretchable health-monitoring sensor, it is necessary to develop advanced functional materials and fabrication technologies. Among the various developed materials and fabrication processes for wearable sensors, carbon-based materials and textile-based configurations are considered as promising approaches due to their outstanding characteristics such as high conductivity, lightweight, high mechanical properties, wearability, and biocompatibility. Despite these advantages, in order to realize practical wearable applications, electrical and mechanical performances such as sensitivity, stability, and long-term use are still not satisfied. Accordingly, in this review, we describe recent advances in process technologies to fabricate advanced carbon-based materials and textile-based sensors, followed by their applications such as human activity and electrophysiological sensors. Furthermore, we discuss the remaining challenges for both carbon- and textile-based wearable sensors and then suggest effective strategies to realize the wearable sensors in health monitoring

A new method for manufacturing dry electrodes on textiles. Validation for wearable ECG monitoring

[EN] This paper presents a new dry ECG electrode printed on a textile substrate. The proposed manufacturing process permits cost-effective mass production. The ECG dry electrode is obtained through screen printing a conductive silver ink coated with a biocompatible carbon layer. Three different designs combining two shapes (circular and square) and two sizes were developed. The resulting measured impedances are similar to those obtained via a conventional electrode. The prototypes were attached to a bracelet and used with a commercial electrocardiogram (ECG) device to register ECG signals. The dry electrodes were validated via ECG monitoring and compared with a conventional wet electrode. The clinical interest intervals reported similar results and the QRS morphology presented slight differences. Noise evaluation showed no notable differences for all the analyzed parameters.The work presented was funded by the Conselleria d'Economia Sostenible, Sectors Productius i Treball, through IVACE. HYBRID II Project, IMAMCI/2021/1. This work was also supported by PID2019-109547RB-I00 (National Research Program, Ministerio de Ciencia e Innovacion, Spanish Government) & CIBERCV CB16/11/00486 (Instituto de Salud Carlos III)Ferri, J.; Llinares Llopis, R.; Segarra, I.; Cebrián Ferriols, AJ.; Garcia-Breijo, E.; Millet Roig, J. (2022). A new method for manufacturing dry electrodes on textiles. Validation for wearable ECG monitoring. Electrochemistry Communications. 136:1-8. https://doi.org/10.1016/j.elecom.2022.1072441813

A washable silver-printed textile electrode for ECG monitoring

Electrocardiography (ECG) is one of the most widely used diagnostic methods to examine the development of cardiovascular diseases (CVD). It is important to have a long-term continuous ECG recording to properly monitor the heart activity, which can be measured by placing two or more electrodes on the skin. Ag/AgCl gelled electrodes are often used for the ECG measurement, but they are not suitable for long-term monitoring due to the dehydration of the gel over time and skin irritation. Textile-based electrodes could have an important role in replacing the gelled electrodes and avoid their associated problems. This paper focuses on the development of a textile-based electrode and studying its ECG detecting performance. We developed silver printed textile electrodes via a flat-screen printing of silver ink on knitted polyester fabric. The surface resistance of silver-coated PET fabric was 1.78 Ω/sq and 3.77 Ω/sq before and after washing, respectively. Stretching of the conductive fabric from 5% to 40% caused a 6% to 18.28% increase in surface resistance. The silver-printed PET fabric stayed reasonably conductive after washing and stretching which makes it suitable for wearable applications. Moreover, the ECG measurement at static condition showed that the signal quality collected before and after washing were comparable with the Ag/AgCl standard electrodes. The P, QRS, T waveforms, and heartbeat before washing in respective order were 0.09 mV, 1.20 mV, 0.30 mV for the silver printed fabric electrode and 72 bpm, and 0.10 mV, 1.21 mV, 0.30 mV, and 76 bpm for Ag/AgCl standard electrode