Electrophysiological Electrodes Research Articles

Nanoscale Strategies for Enhancing the Performance of Adhesive Dry Electrodes for the Skin.

High-quality electrophysiological monitoring requires electrodes to maintain a compliant and stable skin contact. This necessitates low impedance, good skin compliance, and strong adhesion to ensure continuous and stable contact under dynamic conditions. In this context, adhesive epidermal dry electrodes are advancing rapidly, which is promising for long-term applications in clinical diagnosis, wearable health monitoring, and human-machine interfaces. However, challenges persist, as conventional technologies usually fall short of meeting the high standards required for electrophysiological electrodes. This Perspective discusses four key aspects for high-performance epidermal electrodes from an adhesive perspective: initial adhesion, water resistance, dynamic stability, and removal simplicity. We review recent nanoscale strategies addressing these issues, providing a comprehensive guideline to enhance the application performance of epidermal dry electrodes. Additionally, we explore key nanoscale strategies and their associated functions, future technology roadmaps, and prospects for dry adhesive epidermal electrodes.

Synchronized ultrasonography and electromyography signals detection enabled by nanocellulose based ultrasound transparent electrodes

Accurate evaluation of electrophysiological and morphological characteristics of the skeletal muscles is critical to establish a comprehensive assessment of the human neuromusculoskeletal function in vivo. However, current technological challenges lie in unsynchronized and unparallel operation of separate acquisition systems such as surface electromyography (sEMG) and ultrasonography. Key problem is the lack of ultrasound transparency of current electrophysiological electrodes. In this work, ultrasound (US) transparent electrode based on cellulose nanofibrils (CNF) substrate are proposed to solve the issue. US transparency of the electrodes are evaluated using a standard US phantom. The effects of nanocellulose type and ion-bond introduction on electrode performance is investigated. Simultaneous US image and sEMG signal acquisition of biceps brachii during isometric muscle contraction are studied. Reliable correlation analysis of the US and sEMG signals is realized which is rarely reported in the previous literatures. Recyclability and biodegradability of the current electrode are evaluated. The reported technology opens up new pathways to provide coupled anatomical and electrical information of the skeletal muscles, enables reliable anatomical and electrical information correlation analysis and largely simplify the sensor integration for assessment of the human neuromusculoskeletal function.

Light-Based 3D Multi-Material Printing of Micro-Structured Bio-Shaped, Conducting and Dry Adhesive Electrodes for Bioelectronics.

In this work, a new method of multi-material printing in one-go using a commercially available 3D printer is presented. The approach is simple and versatile, allowing the manufacturing of multi-material layered or multi-material printing in the same layer. To the best of the knowledge, it is the first time that 3D printed Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) micro-patterns combining different materials are reported, overcoming mechanical stability issues. Moreover, the conducting ink is engineered to obtain stable in-time materials while retaining sub-100µm resolution. Micro-structured bio-shaped protuberances are designed and 3D printed as electrodes for electrophysiology. Moreover, these microstructures are combined with polymerizable deep eutectic solvents (polyDES) as functional additives, gaining adhesion and ionic conductivity. As a result of the novel electrodes, low skin impedance values showed suitable performance for electromyography recording on the forearm. Finally, this concluded that the use of polyDES conferred stability over time, allowing the usability of the electrode 90 days after fabrication without losing its performance. All in all, this demonstrated a very easy-to-make procedure that allows printing PEDOT:PSS on soft, hard, and/or flexible functional substrates, opening up a new paradigm in the manufacturing of conducting multi-functional materials for the field of bioelectronics and wearables.

Extraction of Ag3Sn nanowires bundle and its electrochemical characteristics

The Ag3Sn nanowires (NWs) bundle embedded in the Sn-3.5Ag eutectic alloy bar directionally solidified was extracted by utilizing electrochemical selective corrosion, during which the Sn-base was dissolved and the Ag3Sn fibrous phase was remained. The diameter of Ag3Sn NWs decreases with the increasing of directional solidification rate, and their length increases with the corrosion duration. Utilizing the electrochemical alternative current (AC) impedance method and the cyclic voltammetry (CV), the interfacial impedance and the charge storage capacity of electrodes with Ag3Sn NWs bundle were tested in 0.9 % NaCl aqueous solution. The measuring results indicated that the lowest interfacial impedance appeared at the average length of nanowires with 8 µm, whereas the charge storage capacity was increased constantly with the length of Ag3Sn NWs. These electrochemical characteristics make the Ag3Sn NWs bundle electrodes possible to be applied as the electrophysiological electrode. A series of trial EEG (electroencephalogram) tests showed that the EEG signals of Ag3Sn NWs dry electrodes had a higher correlation to that of Ag/AgCl wet electrodes.

Flexible Dry Epidermal Electrophysiological Electrodes Based on One-Dimensional Platinum-Coated Silver Nanowires

Flexible Dry Epidermal Electrophysiological Electrodes Based on One-Dimensional Platinum-Coated Silver Nanowires

Smart epidermal electrophysiological electrodes: Materials, structures, and algorithms

Epidermal electrophysiological monitoring has garnered significant attention for its potential in medical diagnosis and healthcare, particularly in continuous signal recording. However, simultaneously satisfying skin compliance, mechanical properties, environmental adaptation, and biocompatibility to avoid signal attenuation and motion artifacts is challenging, and accurate physiological feature extraction necessitates effective signal-processing algorithms. This review presents the latest advancements in smart electrodes for epidermal electrophysiological monitoring, focusing on materials, structures, and algorithms. First, smart materials incorporating self-adhesion, self-healing, and self-sensing functions offer promising solutions for long-term monitoring. Second, smart meso-structures, together with micro/nanostructures endowed the electrodes with self-adaption and multifunctionality. Third, intelligent algorithms give smart electrodes a “soul,” facilitating faster and more-accurate identification of required information via automatic processing of collected electrical signals. Finally, the existing challenges and future opportunities for developing smart electrodes are discussed. Recognized as a crucial direction for next-generation epidermal electrodes, intelligence holds the potential for extensive, effective, and transformative applications in the future.

Electrically conductive and highly compressible anisotropic MXene-wood sponges for multifunctional and integrated wearable devices

Although piezoresistive sensors have wide applications in human motion detection and wearable electronics, it is still a challenge to produce multifunctional and integrated sensors with wide working ranges and linear sensing responses. Herein, electrically conductive, highly compressible, and structurally anisotropic MXene-wood (MW) sponges are fabricated by converting balsa wood blocks to compressible wood sponges with extremely low density and highly anisotropic porous structure, followed by decorating with conductive MXene sheets. The MW sponge is utilized to assemble a piezoresistive sensor with a large working range of 0-25 kPa, wide linear sensing ranges of 5%-50% and 0-180o, and excellent long-term reliability under a bending angle of 30° for 5000 cycles. Additionally, the sensor is suitable for monitoring practical human physiological signals including pulse beating, and finger and wrist bending. An all-MW sponge-based multifunctional and integrated sensing system is constructed by integrating the MW sponge piezoresistive sensor, the MW sponge-based solid-state supercapacitor, and the MW sponge electrophysiological electrodes. The sensing system can concurrently detect surface electromyogram and tactile pressures, and hence realize real-time closed-loop controls. The multifunctional and integrated MW sponge sensing system would have great potentials in real-time pressure recognition and human-machine interfaces.

3D Printed Dry Electrodes for Electrophysiological Signal Monitoring: A Review (Adv. Mater. Technol. 7/2023)

3D Printed On-Skin Electrodes In article number 2201677, Nazek El-Atab and colleagues review various 3D printing and manufacturing techniques of dry electrophysiological electrodes. This review provides a reference guide about various state-of-the-art 3D printing methodologies and materials that have been developed with a wide range of characteristics, including conductivity, flexibility, softness, adhesion, breathability, and biocompatibility with a focus on the main applications in electrocardiogram, electrooculogram, electromyogram, and electroencephalogram.

3D Printed Dry Electrodes for Electrophysiological Signal Monitoring: A Review

Abstract3D printed on‐skin electrodes are of notable interest because, unlike traditional wet silver/silver chloride (Ag/AgCl) on‐skin electrodes, they can be personalized and 3D printed using a variety of materials with distinct properties such as stretchability, conformal interfaces with skin, biocompatibility, wearable comfort, and, finally, low‐cost manufacturing. Dry on‐skin electrodes, in particular, have the additional advantage of replacing electrolyte gel, which dehydrates and coagulates with prolonged use. However, issues arise in performance optimization with the recently discovered dry materials. These challenges become even more critical when the on‐skin electrodes are scaled down to a miniaturized size, making the detection of various biosignals while keeping mechanical resilience under several conditions crucial. This review paper aims to provide researchers interested in the 3D printing and manufacturing field for healthcare applications, specifically dry electrophysiological (EP) on‐skin electrodes and biosignal sensing methodologies, with a reference guide about the various state‐of‐the‐art 3D printing techniques and materials that have been developed with a focus on the main applications of EP electrodes, such as an electrocardiogram, electrooculogram, electromyogram, and electroencephalogram.

A Nanoporous Carbon‐MXene Heterostructured Nanocomposite‐Based Epidermal Patch for Real‐Time Biopotentials and Sweat Glucose Monitoring

AbstractDespite substantial progress in the development of wearable and flexible monitoring systems that conform to the epidermis, most designs focus on either physiological signs such as the electrocardiogram (ECG) results, respiration rate, or metabolites, and ignore the dynamic fluctuations of pH and temperature in sweat during on‐body tests. An advanced butterfly‐inspired hybrid epidermal biosensing (bi‐HEB) patch is presented here, which is interfaced with a custom‐developed miniaturized monitoring system. The patch incorporates a novel transducing layer of nanoporous carbon and MXene (NPC@MXene) for sensitive and durable detection of biomarkers in sweat. The bi‐HEB patch is composed of a glucose biosensor accompanied by pH and temperature sensors to precisely quantify glucose as well as two biopotential electrodes, allowing real‐time recording of electrophysiological (EP) signals. The NPC@MXene‐based glucose biosensor demonstrates an excellent sensitivity of 100.85 µAmm−1 cm−2 within physiological levels (0.003−1.5 mm), and variations in pH and temperature during on‐body perspiration monitoring are calibrated by employing a correction approach. In parallel, the EP electrodes exhibit skin‐electrode contact impedance and biopotential signals similar to those of conventional Ag/AgCl electrodes. Finally, the bi‐HEB patch integrated wearable system is used to accurately monitor sweat glucose and ECG of human subjects participating in indoor physical activities.

Highly Conductive and Underwater Stable Ionic Skin for All‐Day Epidermal Biopotential Monitoring

AbstractEpidermal biopotential monitoring is an essential part of wearable healthcare. For 24 × 7 h detection of electrophysiological signals, commercialized gel electrodes cannot satisfy the demands, in particular for monitoring in humidity or underwater. Epidermal electrodes that can be stable and operated underwater are required. Here, a highly conductive and optically camouflaged ionic skin for epidermal biopotential monitoring under aquatic circumstances is designed. There is a fluorine‐dipole interaction system consisting of fluorine‐rich segment in the polyurethane backbone and fluorine‐cation bonded 1‐ethyl‐3‐methylimidazolium bis(trifluoromethyl‐sulfonyl) imide ([EMIM]+ [TFSI]−) ion pairs distributed in the polymer matrix. Benefitting from the fluorine‐cation interaction, the ionic skin gains remarkable ionic conductivity (1.04 × 10−3 S cm−1), high optical transmittance (92%), and improved mechanical strength (3.1 MPa of Young's modulus). Via cations caught by fluorine‐rich segments, its ionic conductivity can keep stable even by rinsing or fierce washing in water. The epidermal electrode based on such ionic skin can accurately measure a variety of electrophysiological signals undboth atmospheric and aquatic environments, exhibiting robust and excellent signal quality. As the first demonstration of ionic skin‐based electrophysiological electrodes, the ionic skin paves a new way for all‐day wearable healthcare.

Tissue-like electrophysiological electrode interface construction by multiple crosslinked polysaccharide-based hydrogel

A reliable electrophysiological electrode interface (EEI) between bioelectronic devices and biological tissues is indispensable to achieve the high fidelity recording of bioelectricity. However, there is an inherent tradeoff among EEI's electrochemical characteristics, mechanical properties and biocompatibility when considering the desired nanostructure and optimum composition. Here, we proposed a mechanically matched, highly conductive and biocompatible EEI, a tissue-like metal-doped hydrogel which could enable excellent electro-biosensing, by bringing disulfide modified silver nanowires into difunctional hyaluronan/carboxymethyl chitosan composite. The intensity of cortical signals at specific frequency domain recorded by the hydrogel-based EEI is doubled, which is significant for the diagnosis of epilepsy. Furthermore, the natural gel matrix could lead to seamless bio-integration between EEI and the tissue site of interest, minimizing signal dissipation without causing obvious inflammatory response. Overall, the EEI we designed contributes to improving tissue-device integration as well as bioelectronic device's performance and further leads to more effective human-computer interfaces.

A Bioinspired Sweat‐Drainable Janus Electrophysiological Electrode for Scientific Sports Training

AbstractRecent technological innovations in wearable electronics offer possibilities to perform real‐time monitoring of electrophysiological parameters, such as ECG, EMG, and EEG. To achieve accurate and long‐term electrophysiological measurement, great signs of progress have been made in the skin–electrode interfacial problems; nevertheless, the challenges related to sweat have not been fully resolved. Excessive sweat between human skin and the electrode usually fails to achieve a conformal and intact contact, and the nonconductive barriers will lead to a high skin–electrode impedance. Inspired by the structure of liquid directional movement in nature, a Janus gold nanowires/nitrocellulose (AuNWs/NC) electrophysiological electrode with conical micropores is developed to solve interfacial problems caused by sweat. The Janus AuNWs/NC electrodes spontaneously wick sweat from the AuNW side to the NC side, thus keeping intimate skin–electrode contact and low interfacial impedance to ensure a high‐fidelity signal during the long‐term monitoring. By integrating Janus AuNWs/NC electrode with circuit modules and advanced algorithms, a real‐time visualization system is developed for muscle activity intensity. This system is applied to precisely evaluate the muscle controllability and assess the muscle balance ability, which presents great potentials for health monitoring, sports training, and the areas of human–computer interaction.

Arecoline Induces an Excitatory Response in Ventral Tegmental Area Dopaminergic Neurons in Anesthetized Rats.

Arecoline is the principle psychoactive alkaloid in areca nuts. Areca nuts are chewable seeds of Areca catechu L., which are epidemic plants that grow in tropical and subtropical countries and cause dependency after long-term use. However, the mechanisms underlying such dependency remain largely unclear, and therefore, no effective interventions for its cessation have been developed. The present study aimed to examine the effects of arecoline on neurons of the ventral tegmental area (VTA). After rats were anesthetized and craniotomized, electrophysiological electrodes were lowered into the VTA to obtain extracellular recordings. The mean firing rate of dopaminergic and GABAergic neurons were then calculated and analyzed before and after arecoline treatment. The burst characteristics of the dopaminergic neurons were also analyzed. The results showed that arecoline evoked a significant enhancement of the firing rate of dopaminergic neurons, but not GABAergic neurons. Moreover, arecoline evoked remarkable burst firings in the dopaminergic neurons, including an increase in the burst rate, elongation in the burst duration, and an enhancement in the number of spikes per burst. Collectively, the findings revealed that arecoline significantly excited VTA dopaminergic neurons, which may be a mechanism underlying areca nut dependency and a potential target for areca nut cessation therapy.

Evaluation of the effectiveness of interventional treatment of ventricular arrhythmias of rare localizations using non-invasive mapping

Background. Atypical localization of the focus of ventricular arrhythmias is a rather difficult group for invasive mapping and subsequent radiofrequency ablation. Invasive electroanatomical mapping, multipolar electrophysiological electrodes in combination with electrophysiological study for searching an early zone of arrhythmia focus, and substrate mapping, are aimed to identifying critical areas of the arrhythmia contour. However, there are still situations in which arrhythmia cannot be eliminated, despite the use of these systems. The method of superficial non-invasive mapping of the heart seems to be relevant, which makes it possible to estimate the volume of surgery and select the necessary technology to eliminate arrhythmias.Aim. To compare the effectiveness of interventional treatment of patients with ventricular arrhythmias of atypical localization with and without the use of superficial non-invasive mapping.Methods. The study included 40 patients with ventricular arrhythmias of rare localization. The patients were divided into two groups. Group I included 21 patients who underwent non-invasive superficial and invasive electrophysiological cardiac mapping. Group II included 19 patients who underwent invasive electrophysiological cardiac mapping.Results. Over a follow-up period of 12 months, the freedom from arrhythmia in group I was 76%, in group II — 61%. The total operation time, duration and dose of fluoroscopy were less in group I compared to the group II.Conclusion. The study results demonstrated that the method of non-invasive surface mapping of the heart is highly effective in ventricular arrhythmias of atypical localization. The time of radiofrequency ablation, interventional intervention, fluoroscopy is lower with the use of superficial non-invasive mapping, compared with the control group. Received 13 July 2021. Revised 20 October 2021. Accepted 9 December 2021. Funding: This work is supported by a grant of the Russian Science Foundation (project No. 19-15-00406). Conflict of interest: The authors declare no conflict of interest. Contribution of the authorsConception and study design: E.A. Artyukhina, A.Sh. RevishviliData collection and analysis: E.A. Artyukhina, M.V. Yashkov, E.V. Dedukh, I.A. Taymasova, A.Sh. RevishviliStatistical analysis: M.V. YashkovDrafting the article: E.A. Artyukhina, M.V. YashkovCritical revision of the article: E.A. Artyukhina, M.V. Yashkov, A.Sh. RevishviliFinal approval of the version to be published: E.A. Artyukhina, M.V. Yashkov, E.V. Dedukh, I.A. Taymasova, A.Sh. Revishvili

Preparation and application of self-adhesive ultra-thin epidermal electrophysiological electrodes

<p indent="0mm">Flexible and wearable epidermal electrophysiological electrodes are of great significance in the field of artificial intelligence and life health. The acquisition of stable epidermal electrophysiological signals with high-quality is the key to wearable monitoring of electrophysiological signals of human bodies. Ag/AgCl gel-electrodes commonly used in clinical diagnosis still have a large number of shortcomings, including serious discomfort and inevitable motion artifacts during long-term use. Therefore, it is urgent to develop electrophysiological electrodes that can be worn on the epidermis for a long time and can effectively avoid motion artifacts. The self-adhesive electrode with a Young’s modulus similar to that of the skin and an extremely thin thickness <sc>(&lt;1 μm)</sc> is a typical electrode that meets the above requirements. This paper introduces the research progress of this type of epidermal electrophysiological electrodes in detail. According to the different types of materials, the design idea, basic characteristics, advantages and disadvantages of wearing are summarized. Meanwhile, the applications of self-adhesive ultra-thin electrodes in medical diagnosis and analysis and human-machine interface are discussed, and we are looking forward to the opportunities and challenges of the electrode in collecting electrophysiological signals.

3D printed leech-inspired origami dry electrodes for electrophysiology sensing robots

In this study, based on inspiration drawn from origami and the suction mechanism of leeches, a dry electrode is developed for reliable blood pressure (BP) monitoring. The leech-inspired suction mechanism generated a local soft vacuum facilitating appropriate contact with the human skin. Subsequently, an electrocardiogram (ECG) sensor, termed a leech-inspired origami (LIO) sensor, was constructed using the developed dry electrode. The LIO with a sensing robot system ensures reliable ECG signals with a signal-to-noise ratio of 21.7 ± 0.56 dB. From the paired detection of ECG and photoplethysmography (PPG) through human–robot interaction, BP monitoring was demonstrated. The average difference of the systolic BP between that estimated by the sensing robot and that monitored by the sphygmomanometer was 0.03 mmHg, indicating the reliable BP monitoring ability of the sensing robot. The LIO sensing system inspired by origami and leech behaviors makes BP sensing tools feasible, which in turn would further the development of a remote healthcare monitoring robotic system.

Ultrafast self-healing and self-adhesive polysiloxane towards reconfigurable on-skin electronics

We develop a novel polysiloxane elastomer with ultrafast self-healing capability, robust mechanical properties, universal self-adhesiveness, and reconfigurability towards any shapes, which is potential for on-skin electrophysiological electrodes.

Radiofrequency renal artery denervation: technical issues of different approaches and safety

Objective . To describe the technical issues and safety of renal denervation (RD) when using a multielectrode radiofrequency (RF) bipolar balloon catheter, a multielectrode unipolar RF spiral catheter, and an electrophysiological (EP) 3,5-mm RF ablation catheter. Design and methods . Between 2016 and 2019, 54 patients undergoing renal artery (RA) denervation were included into a prospective observational study: 27 procedures were performed using the balloon technology, 21 — using the spiral; and 6 — using a steerable irrigated EP catheter under three-dimensional electroanatomical guidance. In 50 patients RD was performed due to resistant arterial hypertension, and in 4 — due to intractable ventricular tachyarrhythmias. Results . The use of the spiral catheter was associated with a higher number of RF points in the RA, when compared with balloon ablation and EP catheter ablation (22,3 ± 9,6 vs. 13,4 ± 5,5 vs. 8,7 ± 2,1, p &lt; 0,01). In the balloon ablation group, a direct correlation between the number of RF points and the sharpest RA angle was found (correlation coefficient — 0,82). We observed the following complications: in the balloon ablation group — 1 dissection of the RA and 1 aneurysm of the right femoral artery (7,4 %); in the spiral ablation group — 1 aneurysm and 1 pulsating hematoma of the right femoral artery (9,5 %); in the electrophysiological electrode ablation group — 1 dissection of the RA, 1 aneurysm of the right femoral artery (33,4 %). Conclusions . The use of the spiral multielectrode catheter is associated with the higher number of RF applications, including ablation inside distal branches. The number of RF points depends on the artery tortuosity when performing balloon-based ablation. Manipulations inside the RA using the EP catheter might not be safe.

Multifunctional Electronic Textiles Using Silver Nanowire Composites.

Textiles represent an appealing platform for continuous wearable applications due to the exceptional combination of compliance, water vapor permeability, and comfortableness for long-term wear. We present mechanically and electrically robust integration of nanocomposites with textiles by laser scribing and heat press lamination. The simple and scalable integration technique enables multifunctional E-textiles without compromising the stretchability, wearability, and washability of textiles. The textile-integrated patterns exhibit small line width (135 μm), low sheet resistance (0.2 Ω/sq), low Young's modulus, good washability, and good electromechanical performance up to 50% strain, which is desirable for wearable and user-friendly electronic textiles. To demonstrate the potential utility, we developed an integrated textile patch comprising four dry electrophysiological electrodes, a capacitive strain sensor, and a wireless heater for electrophysiological monitoring, motion tracking, and thermotherapy, respectively. Beyond the applications demonstrated in this paper, the materials and methods presented here pave the way for various other wearable applications in health care, activity tracking, rehabilitation, sports medicine,and human-machine interactions.