Effect of Ag/AgCl paste on the performance of screen-printed flexible Ag/AgCl biomedical electrodes

Effect of Ag/AgCl paste on the performance of screen-printed flexible Ag/AgCl biomedical electrodes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Effect of Ag/AgCl paste on the performance of screen-printed flexible Ag/AgCl biomedical electrodes Wei Li, Qingyue Luo, Danlei Jing, Yongqing Hu, Hu Sun, Xianglei Yu, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7462900/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The Ag/AgCl electrode has been widely used in biomedical electrodes due to its many advantages. In recent years, Ag/AgCl electrode materials prepared by screen printing method have attracted extensive research interest, but the effect of Ag/AgCl paste on the performance of screen-printed flexible Ag/AgCl electrodes has been neglected. In this paper, the effects of different types and contents of silver powder on the conductivity and microstructure of Ag/AgCl paste electrode were studied, to optimize the best type of silver powder and the ratio of Ag: AgCl for paste preparation. The structure of the Ag/AgCl electrode was designed, and the performance of the fabricated Ag/AgCl electrode was evaluated using an electrochemical workstation, an impedance tester, and an electrocardiogram detection system. When flaky silver powder H with high specific surface area is used and the ratio of Ag:AgCl is 5:5, the prepared electrode can meet the requirements of electrocardiogram testing. Physical sciences/Chemistry Physical sciences/Materials science Ag/AgCl electrode screen printing conductivity ratio of Ag: AgCl electrocardiogram testing Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction With the continuous development of chemical sensors, biosensors and biomedical electrodes in the fields of health and medical treatment, food and soil quality, climate change and environmental protection, higher requirements are put forward for the corresponding reference electrodes in terms of reliable performance, low cost, designability and flexibility.[ 1 – 4 ] Ag/AgCl electrode has the advantages of low polarization, low impedance, simple manufacture and sensitivity to low frequency electric field, which makes it surpass the standard hydrogen electrode and saturated calomel electrode in application scope. Furthermore, with its minimal and stable half-cell potential, the non-polarized Ag/AgCl electrode satisfies the requirements for biomedical electrodes, including good conductivity, robust stability, minimal potential fluctuation, and low polarization potential.[ 5 – 7 ] Its widespread use in clinical monitoring and biomedical measurements underscores its significance.[ 8 – 10 ] Therefore, Ag/AgCl electrode materials have aroused extensive research interest. Various methods exist for preparing Ag/AgCl electrodes, the classical structure of the Ag/AgCl electrode is a glass shell structure, prepared by electrolytic chlorination, which has excellent stability. However, due to the extremely brittle, rigid and bulky structure of traditional glass electricity, its further application is limited.[ 11 , 12 ] The silver/silver chloride electrode prepared by powder tablet method can be obtained with excellent performance, due to it enhances the close contact and dispersion of Ag/AgCl particles at a certain temperature and pressure. Nevertheless, this method has complicated procedures, high cost and is not easy for mass production.[ 13 ] In addition, Ag/Ag electrodes can also be prepared by thermoelectrolysis and other methods,[ 14 , 15 ] but they can not meet the requirements of flexible, low cost, good flexibility and so on. Transforming Ag and AgCl powder into a low-temperature curable paste for screen printing on a special substrate offers significant advantages.[ 16 , 17 ] This method boasts flexible design, compact size, simple structure, low cost, excellent repeatability, high consistency, and suitability for industrial production.[ 18 , 19 ] In biomedicine, this electrode offers significant research value and a vast potential market by meeting the low-cost, customizable, and flexible needs of medical and reference electrodes.[ 20 – 22 ] The Ag/AgCl reference electrode requires an internal electrolyte to achieve ideal performance. In order to achieve stable and low-cost Ag/AgCl electrode preparation and make industrial production possible, many researchers mainly focus on the improvement of internal electrolytes. The development of electrolytes such as poly(vinyl acetate) ink containing KCl and paste of sodium alginate containing KCl improved the potential stability and extended the maintenance time effectively.[ 11 , 23 ] However, in recent years, the preparation of low-cost and disposable Ag/AgCl reference electrodes has aroused great interest among researchers. Therefore, it is also a popular research direction to successfully prepare Ag/AgCl pseudo-reference electrode with stable performance by optimizing printing method, electrode treatment and preparation process.[ 24 – 26 ] Among them, Musa et al. developed d a potentiometric system composed of an Ag/AgCl QRE and a pH-electrode (ISM deposited on a graphite electrode) that can be used continuously for a period of not less than 7 days in aqueous solutions. The open-circuit potential measurement performance is that the standard deviation of the open-circuit potential of the electrode is ± 1.2 mV over a period of 7 days, which shows good potential stability. At the same time, an average pH sensitivity of (-60.8 ± 1.7) mV/pH per pH unit is achieved in the pH range of 7.00 ~ 7.63.[ 26 ] Interestingly, Silva et al. fabricated an ink-jet printed solid-state Ag/AgCl pseudo-reference electrode on PET or chromatographic paper substrates. A silver nanoparticle paste with 20wt% ethylene glycol was applied onto PET or paper substrates using a printing machine. Following curing, the printed silver layer was briefly immersed in a 40 mg/mL NaClO solution to create a silver chloride layer. This preparation technique is suitable for mass-producing solid Ag/AgCl pseudo-reference electrodes in various structures and sizes. The open-circuit potential of the prepared Ag/AgCl pseudo-reference electrode closely matched that of commercial counterparts. The Ag/AgCl pseudo-reference electrode demonstrated excellent reproducibility and stability within 30 minutes, with no significant change observed after 30 days of dark storage.[ 24 ] With the development of biomedical electrodes, higher requirements are put forward for the potential and impedance of Ag/AgCl reference electrodes. As an important part of the reference electrodes, Ag/AgCl pastes seriously affect electrical properties of reference electrode, but there are almost no relevant studies on Ag/AgCl pastes. Consequently, This paper investigates how the specific surface area of Ag powder and the Ag:AgCl ratio affect the resistivity of paste, hydration reaction, long-term stability and electrode potential of Ag/AgCl electrodes. Finally, this paper compares the practical application of self-made and commercial Ag/AgCl reference electrodes in impedance testing and obtains a satisfactory result, at the same time, it is confirmed by Electrocardiogram(ECG) testing that the self-made Ag/AgCl electrode meets the requirements of ECG test. This makes it possible to commercialize the self-made Ag/AgCl electrode in this study, and this paper also provides theoretical reference for the development of Ag/AgCl electrode. 2. Experiment 2.1. Materials and experimental equipment This study utilized the following chemicals: low diameter/thickness ratio flaky Ag powder L (specific surface area: 0.57 m 2 /g, from Sino-Platinum Metals Co., Ltd.), high diameter/thickness ratio flaky Ag powder H (specific surface area: 1.24 m 2 /g, from Sino-Platinum Metals Co., Ltd.), NaCl (≥ 99.5%, from Sinopharm Chemical Reagent Co., Ltd.), AgNO 3 (≥ 99.8%, from Sinopharm Chemical Reagent Co., Ltd.), and modified bisphenol A epoxy (from Sino-Platinum Metals Co., Ltd.). Three-roll grinder (MTR-50EP, WINNER) is used for Ag/AgCl pastes rolling, high-resolution screen printing machine(TY-CP6090B, CHNTOP) is used for electrode printing, cold-field emission scanning electron microscope (SU8010, HITACHI) is used for electrode micro-morphology observation, electrochemical workstation (600E, CH Instruments) is used for electrode potential and cyclic voltammetric curve testing, impedance analyzer (E4990A, KEYSIGHT) is used for impedance testing, and the ECG detection system is used for ECG testing. 2.2. Preparation of AgCl powder A 0.02 mol/L AgNO 3 solution was gradually added to an excess 0.02 mol/L NaCl solution, with continuous stirring, to form an AgCl suspension. Following repeated centrifugation and washing, excess chloride ions were removed until the supernatant showed no turbidity upon titration with AgNO 3 solution. The sediment was then washed three times with alcohol through centrifugation and subsequently placed in a constant-temperature drying oven. AgCl powder was prepared by drying at 70°C for 6 hours. Since AgCl is easily decomposed under visible light, the whole preparation process must be carried out in a dark room or under dark conditions. 2.3. Preparation of Ag/AgCl pastes Prepared AgCl powder, flaky Ag powder, and modified bisphenol A epoxy were mixed in the agate mortar according to a specific ratio. Subsequently, a three-roll mill is used for secondary mixing and rolling until the fineness is reduced to less than 10µm, at which point the Ag/AgCl paste was ready. The mass ratio of Ag/AgCl powder to resin used in this paper was 3:2. Two types of silver powder were used: flaky Ag powder L with low diameter-thickness ratio and flaky Ag powder H with high diameter-thickness ratio. The microstructure of different types of silver powders is shown in Fig. 1 . Two types of flaky Ag powder and AgCl powder were combined into 10 paste groups based on various mass ratios: (L1, H1) Ag:AgCl = 7:3, (L2, H2) Ag:AgCl = 6:4, (L3, H3) Ag:AgCl = 5:5, (L4, H4) Ag:AgCl = 4:6, and (L5, H5) Ag:AgCl = 3:7. 2.4. Ag/AgCl electrode design Figure 2 shows the structure diagram of the Ag/AgCl electrode. The preparation process is as follows: firstly, self-made silver paste with low temperature and high conductivity is printed on PET film. This was followed by oven curing at 150°C for 15 minutes to form the base silver electrode. Subsequently, the Ag/AgCl paste was printed onto the silver electrode and oven-cured at 150°C for 15 minutes to solidify the Ag/AgCl electrode layer. Finally, a protective isolation resin was applied to the center of the electrode assembly. 2.5. Conductivity characterization of Ag/AgCl paste Ten groups of Ag/AgCl electrode pastes were printed onto PET film, with ten samples in each group. Following curing, a multifunctional four-point probe tester was used to measure the sheet resistance of the Ag/AgCl electrodes. Subsequently, the thickness of the Ag/AgCl electrodes was determined using a film thickness gauge, allowing for the calculation of their resistivity. 2.6. Electrochemical characterization of Ag / AgCl electrode The self-made Ag/AgCl electrode served as the working electrode, with a commercial saturated potassium chloride Ag/AgCl reference electrode and a platinum auxiliary electrode comprising the three-electrode system. Electrochemical workstations were used to characterize the electrode potential stability, hydration period, cyclic voltammetry, and consistency across different solution environments. 2.7. Impedance test of Ag/AgCl electrode The impedance of the self-made Ag/AgCl electrode was measured with an impedance analyzer, using a hydrogel layer between two identical electrodes as the sample, and then compared to the impedance of a commercial Ag/AgCl electrode. 2.8. Ag/AgCl electrode ECG test Through electrochemical and impedance tests, the sample with the best performance is selected and ECG test was observed by ECG detection system. 3. Results and discussion 3.1. The effect of different Ag powder and Ag:AgCl ratio on the conductivity of Ag/AgCl pastes Table 1 displays the resistivity test results for ten groups of Ag/AgCl pastes. Note: The resistance of Ag/AgCl pastes with a 3:7 Ag powder L ratio exceeded the equipment's range, and thus resistivity was not measured. According to the table, for Ag powder H, resistivity increases rapidly when the Ag:AgCl ratio is below 4:6. Similarly, for Ag powder L, resistivity surges when the ratio is below 5:5. Beyond a specific Ag:AgCl ratio, the increase in resistivity becomes negligible. Table 1 Resistivity test results of silver/silver chloride pastes Ag:AgCl High diameter/thickness ratio flaky Ag powder H Lower diameter/thickness ratio flaky Ag powder L Ag/AgCl pastes Resistivity (Ω·m) Standard error Ag/AgCl pastes Resistivity (Ω·m) Standard error 7:3 H1 1.63E-07 0.027 L1 1.77E-07 0.029 6:4 H2 1.87E-07 0.032 L2 2.42E-07 0.025 5:5 H3 2.16E-07 0.035 L3 5.97E-06 0.043 4:6 H4 1.15E-06 0.048 L4 1.76E-02 0.272 3:7 H5 3.24E-03 0.327 L5 - - Figure 3 presents SEM images of the Ag/AgCl electrode's surface morphology. Electron beam irradiation was used to remove the resin layer and expose AgCl particles, as they are wrapped underneath it in the Ag/AgCl electrode. Consequently, resin removal was incomplete in some images, allowing only partial observation of AgCl areas. Figure 3 (a) and (b) show that nano-AgCl particles are dispersed on the flaky silver powder surface without forming agglomerates upon solidification of the L2 and H2 Ag/AgCl pastes. Despite the identical Ag:AgCl ratios in H2 and L2 pastes, the larger specific surface area of Ag powder H results in fewer nano-AgCl particles on its surface. These particles tend to preferentially accumulate at the edges of flaky Ag powder with high surface energy. Figure 3 (c) and (d) reveal that nano-AgCl particles are uniformly distributed on flaky Ag powder H's surface after H3 pastes solidify, with fewer particles near the interfaces where flakes contact. Consequently, this distribution minimally affects the conductive contacts between flaky silver powders. This observation aligns with the phenomenon where the Ag:AgCl ratio in H3 pastes decreases slightly, yet there's a minor increase in paste resistivity. Figure 3 (e) and (f) show that after L3 and H4 pastes solidify, nano-AgCl particles on the flaky Ag powder surface begin to cluster together. The resulting AgCl layer on the flaky Ag powder surface thickens, leading to an increase in electrode resistivity. Figure 3 (g) and (h) illustrate that after L4 and H5 pastes solidify, AgCl particles agglomerate into non-conductive clusters, disrupting flaky Ag powder contact and impeding conductive network formation, thus sharply increasing resistivity. The observed phenomena may result from the lower Ag/Ag interface energy within silver powder mixtures compared to the AgCl/silver and AgCl/AgCl interfaces, and a lower Ag/resin interface energy compared to AgCl powder and resin. At low AgCl powder concentrations, nanoparticles preferentially adsorb on non-contacting surfaces of flaky silver powders. As AgCl powder content increases and nanoparticles fully cover flaky silver powder surfaces, further AgCl nanoparticles cannot form additional Ag-AgCl interfaces. Instead, they tend to form AgCl-AgCl interfaces, causing Ag/AgCl particles to aggregate rather than disperse uniformly in the resin. Increased AgCl agglomeration disrupts contact among flaky silver powders, destroying electrical conduction paths within the electrode and raising resistivity. The larger specific surface area of silver powder H than L allows for more Ag-AgCl interfaces, necessitating a higher proportion of AgCl to increase the Ag/AgCl electrode's resistivity. 3.2 The influence of silver powder and its proportion on the electrochemical characteristics of Ag/AgCl electrode Based on the research findings, pastes H1-H4 (with lower resistivity) and L1-L3 were used to prepare Ag/AgCl electrodes He1-He4 and Le1-Le3, respectively, using the method described in section 2.4 . A three-electrode system was established with the self-made Ag/AgCl electrodes as the working electrodes, commercial Ag/AgCl electrodes as reference electrodes, and platinum electrodes as auxiliary electrodes. The electrode potential stability, hydration period, and cyclic voltammetry curves of the working electrodes in various solutions were measured. 3.2.1 Open circuit voltage test The Ag/AgCl electrode's sensitivity to chloride ion concentrations significantly impacts its performance in various environments. The open circuit voltage of the self-made Ag/AgCl electrode was evaluated using a 0.9% NaCl solution to simulate the sweat environment of the human body. Upon contact with the solution, two equilibrium reactions take place on the surface of the Ag/AgCl electrode, as described below: \(\:{\text{Ag}}_{\text{(aq)}}^{+}+{\text{e}}^{-}\leftrightharpoons\:{\text{Ag}}_{\text{(}\text{s}\text{)}}\) 3 − 1 \(\:{\text{AgCl}}_{\text{(aq)}}^{+}+{\text{Cl}}_{\text{(aq)}}^{-}\leftrightharpoons\:{\text{AgCl}}_{\text{(s)}}\) 3 − 2 The electrode potential of Ag/AgCl satisfies the Nernst equation: \(\:{\text{E}}_{\text{(}{\text{Ag}}^{+}\text{/Ag)}}={\text{E}}_{\text{(}{\text{Ag}}^{\text{+}}\text{/Ag)}}^{0}-\frac{\text{RT}}{\text{nF}}\text{ln}\text{([}{\text{Ag}}^{\text{+}}\text{])}\) 3–3 Where E 0 represents the standard electrode potential (V), n denotes the number of electrons involved in the electrochemical reaction, R is the gas constant (J K-1 mol-1), T stands for the absolute temperature (K), and F is the Faraday constant (C mol-1). The concentration of free Ag + ions is expressed in mol/L. Given that the solubility product of AgCl in aqueous solution remains constant, the theoretical electrode potentials of AgCl can be calculated by input of different concentrations of chloride ions. In a 0.9% NaCl solution, the chloride ion concentration is 0.1540 mol/L, and the corresponding theoretical electrode potential of Ag/AgCl is 0.2704 V at room temperature. At room temperature, the chloride ion concentration in a saturated potassium chloride solution is 3.4030 mol/L, and the corresponding theoretical electrode potential of Ag/AgCl is 0.1908 V. Consequently, the saturated Ag/AgCl electrode serves as the reference electrode for determining Ag/AgCl, with the theoretical open-circuit voltage in a 0.9% NaCl solution estimated at 0.0796 V. Figure 4 displays the open-circuit voltage test results for Ag/AgCl electrodes He1-He4 and Le1-Le3. As can be seen from Fig. 4 , the open circuit voltage of the He2-He4 and Le2-Le3 groups of electrodes is very close to the theoretical voltage of 0.0796V, with deviations under 3 mV. The hydration cycle of He series electrodes is shorter than that of Le series electrodes, likely due to the resin layer's thickness on the electrode's surface. Thinner resin layers allow for quicker equilibrium of electrode potential. Additionally, the larger specific surface area of silver powder H results in a thinner resin layer than that on electrodes using silver powder L, thereby shortening the He group's hydration period relative to the Le group. Comparatively, within each group, electrodes with lower AgCl content exhibit shorter hydration periods than those with higher AgCl content, likely due to the different amounts of chloride ions required to achieve equilibrium. Regarding hydration period, the three groups of Ag/AgCl electrodes, He2-He4, demonstrate satisfactory performance. In terms of long-term stability, the open-circuit voltage changes for electrodes in groups He3 and Le3 were below 1 mV within 24 hours of reaching stability. 3.2.2 Cyclic voltammetry test The redox reversibility of the self-made Ag/AgCl electrode was evaluated using cyclic voltammetry in a saturated potassium chloride solution. Electrochemical workstation parameters were configured with a high potential of 0.8 V, a low potential of -0.8 V, a scanning rate of 0.05 V/s, one scanning cycle, a sampling interval of 0.001 V, and a sensitivity of 0.01 A/V. The experimental results are presented in Fig. 5 . Except for the the He4 electrode, the oxidation and reduction peaks for the four electrode groups are nearly symmetrical, and the He3 electrode is the best. This indicates good redox reversibility across these groups. Combining the test results of open circuit voltage and cyclic voltammetry, electrodes composed of sheet silver powder H with an Ag:AgCl ratio of 5:5 demonstrate better overall performance. They feature a short hydration period, stable open-circuit voltage, and reversible redox reactions. 3.3 impedance test Impedance variations for the five self-made electrode groups (He2-He4, Le2-Le3) and commercial Ag/AgCl cardiac electrodes from Shanghai Junkang Medical Equipment Co., Ltd., across a frequency range of 20-10000 Hz, were assessed using the method outlined in section 2.7 . Results are depicted in Fig. 6 . The five self-made Ag/AgCl electrodes demonstrated lower impedance values compared to the commercial electrode. This may be due to the fact that commercial electrodes are coated with thin AgCl layers on Ag, forming a double-layer structure with a single Ag-AgCl interface. Conversely, the self-made Ag/AgCl pastes ensure a uniform dispersion of AgCl particles on silver powder, yielding a greater number of Ag-AgCl interfaces, resulting in more Ag-AgCl interfaces, thus making the AgCl layer thinner, which stabilizes the electrode structure, enhances electrical conductivity, and reduces impedance. Furthermore, Fig. 6 shows that the impedance of the Ag/AgCl electrode using the same silver powder increases with increasing AgCl content. This change is particularly pronounced in the frequencies between 0-5000 Hz. However, from 5000–10000 Hz, the impedance disparity diminishes, and impedance overall declines as frequency increases. 3.4 ECG test validation The ECG signal detection capabilities of self-made Ag/AgCl paste electrodes He3 was validated using an ECG detection system. Figure 7 displays ECG monitoring results using self-made electrode pastes. As shown in the Fig. 7 , the self-made Ag/AgCl electrode successfully detected ECG signals with clear and complete periodic variations. In group He3, there was minimal noise interference, making the five standard ECG waveforms (P, Q, R, S, T) distinctly visible. The findings indicate that the self-madeHe3 Ag/AgCl electrode is sufficient for medical ECG testing. 4. Conclusion In this paper, Ag/AgCl paste, which is less studied among Ag/AgCl electrode materials system, is taken as the research point. The effects of silver powder type and silver content on the conductivity and microstructure of Ag/AgCl paste was studied. Nano-AgCl particles were observed to preferentially bind to the surface of flaky silver powder, aggregating and thus impacting the electrode's conductivity. Therefore, the AgCl ratio should be maintained below a certain threshold to prevent a rapid increase in electrode resistivity, flaky silver powder with a larger surface area can accommodate a higher proportion of AgCl. Through electrochemical, impedance, and ECG testing, the efficacy of self-made Ag/AgCl electrodes, with silver to silver chloride ratios of 5:5, was confirmed to satisfy ECG testing requirements. The Ag:AgCl = 5:5 electrode exhibits superior open circuit voltage stability, enhanced redox reversibility and reduced impedance. In conclusion, self-made Ag/AgCl electrode achieves the most satisfactory performance, and has a good application prospect in the field of ECG testing. Declarations Conflict of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding This work was funded by the Major Science and Technology project of Yunnan Province (Grant No. 202402AB080005 and 202102AB080008), the Fundamental Research Project of Yunnan Province (Grant No. 202501AS070110), the Science and Technology projects of Yunnan Precious Metals Laboratory (Grant No. YPML-2023050206, YPML-2022050207 and YPML-20240502102). Author Contribution Wei Li: Writing – review & editing, Writing – original draft, Methodology, Data curation, Formal analysis, Validation, Visualization. Qingyue Luo: Writing – review & editing, Writing – original draft, Methodology, Data curation, Formal analysis, Validation, Visualization. Danlei Jing: Writing – review & editing, Conceptualization, Methodology, Data curation, Investigation. Yongqing Hu: Validation. Hu Sun: Investigation. Xianglei Yu: Resources. Bowen Yang: Data curation. Zikai Xiong: Methodology. Jianqiang Wang: Conceptualization, Methodology, Supervision, Visualization. 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Stable Full Inkjet-Printed Solid-State Ag/AgCl Reference Electrode. Anal. Chem. 91 (24), 15539–15546 https://doi.org/10.1021/acs.analchem.9b03441 . (2019). Musa, A. E. et al. Disposable Miniaturized Screen-Printed pH and Reference Electrodes for Potentiometric Systems. Electroanal 23 (1), 115–121. https://doi.org/10.1002/elan.201000443 (2011). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7462900","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":511858956,"identity":"ee00405f-e8be-4518-8493-256198280f7b","order_by":0,"name":"Wei Li","email":"","orcid":"","institution":"Sino-Platinum Metals Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Li","suffix":""},{"id":511858957,"identity":"68dd55db-0c05-45c4-8dac-f07bacf0286a","order_by":1,"name":"Qingyue Luo","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Qingyue","middleName":"","lastName":"Luo","suffix":""},{"id":511858958,"identity":"636810f8-890a-42b6-929d-3e29bb1a487e","order_by":2,"name":"Danlei Jing","email":"","orcid":"","institution":"Kunming Institute of Precious Metals","correspondingAuthor":false,"prefix":"","firstName":"Danlei","middleName":"","lastName":"Jing","suffix":""},{"id":511858959,"identity":"ccd9e17b-ec9a-4704-a46f-76bc305cd6fa","order_by":3,"name":"Yongqing Hu","email":"","orcid":"","institution":"Kunming Institute of Precious Metals","correspondingAuthor":false,"prefix":"","firstName":"Yongqing","middleName":"","lastName":"Hu","suffix":""},{"id":511858961,"identity":"009527a5-a44f-48ed-b26c-9d0d21970ba4","order_by":4,"name":"Hu Sun","email":"","orcid":"","institution":"Sino-Platinum Metals Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Hu","middleName":"","lastName":"Sun","suffix":""},{"id":511858965,"identity":"df4e552d-01ac-46cd-9a7a-ab9b830e1df7","order_by":5,"name":"Xianglei Yu","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Xianglei","middleName":"","lastName":"Yu","suffix":""},{"id":511858967,"identity":"8cf21708-530e-45da-ac61-f2931cc2a7c2","order_by":6,"name":"Bowen Yang","email":"","orcid":"","institution":"Sino-Platinum Metals Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Bowen","middleName":"","lastName":"Yang","suffix":""},{"id":511858968,"identity":"70903d93-0555-420c-a7f8-9952454eb30c","order_by":7,"name":"Zikai Xiong","email":"","orcid":"","institution":"Kunming Institute of Precious Metals","correspondingAuthor":false,"prefix":"","firstName":"Zikai","middleName":"","lastName":"Xiong","suffix":""},{"id":511858970,"identity":"79b7e9d0-2fcd-4f76-9a4d-6ba058c2cffc","order_by":8,"name":"Jianqiang Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAArElEQVRIiWNgGAWjYFCCAwwMCQwMcmzs7QdI02LMx3MmgTS7EudJOBgQp9Tg4OENDA93bEtvkwBa9qNiGxFaDhwrYEg8czu3TbrxAGPPmduEtZgdOGPAkNgG1CJzIIGZsY0ELelsEgkGpGlJIF6LPdQvhm3AQD5IlF8kZxzewPhzx215+fb2gw9+VBChhUHigPkPxgYI+wAR6oGAv8GAAaZlFIyCUTAKRgFWAAA1D0LQhG/GqQAAAABJRU5ErkJggg==","orcid":"","institution":"Sino-Platinum Metals Co., Ltd","correspondingAuthor":true,"prefix":"","firstName":"Jianqiang","middleName":"","lastName":"Wang","suffix":""},{"id":511858974,"identity":"16dc9594-6630-432b-b901-c86dde5f3174","order_by":9,"name":"Junpeng Li","email":"","orcid":"","institution":"Sino-Platinum Metals Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Junpeng","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2025-08-26 12:23:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7462900/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7462900/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90946319,"identity":"44d3815c-23d8-4632-bf38-c846a9ddd50e","added_by":"auto","created_at":"2025-09-09 20:34:04","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":124728,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of flaky Ag powder (a) flaky Ag powder L, (b) flaky Ag powder H\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7462900/v1/3ece87b7aea3b586a741927f.jpg"},{"id":90945923,"identity":"c50a8c00-c8da-4dfb-bb12-7c276e7138eb","added_by":"auto","created_at":"2025-09-09 20:18:03","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":117858,"visible":true,"origin":"","legend":"\u003cp\u003eStructure of Ag/AgCl electrode\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7462900/v1/2e29b30162acad2bcfed48ad.jpg"},{"id":90945927,"identity":"2453508d-f869-4bdf-b0c6-8ea884e846cf","added_by":"auto","created_at":"2025-09-09 20:18:04","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":149910,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of Ag/AgCl electrode surface, (a) H2 paste, (B) L2 paste, (C)(D) H3 paste, (E) L3 paste, (F) H4 paste, (g) L4 paste, (h) H5 paste\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7462900/v1/8e3580ba3a9ce971444985b3.jpg"},{"id":90946175,"identity":"53b5793d-0118-436f-8f29-59dd700edca9","added_by":"auto","created_at":"2025-09-09 20:26:04","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":64272,"visible":true,"origin":"","legend":"\u003cp\u003eOpen-circuit voltage test of Ag/AgCl electrodes in 0.9% NaCl solution\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7462900/v1/2b12de4f6c54a359a7f1a422.jpg"},{"id":90945931,"identity":"bff8d152-beb4-415e-83e2-cfcaba9ab296","added_by":"auto","created_at":"2025-09-09 20:18:04","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":57946,"visible":true,"origin":"","legend":"\u003cp\u003ecyclic voltammetry of Ag/AgCl electrode\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7462900/v1/6d7de593648391b26b8898aa.jpg"},{"id":90946178,"identity":"bd16af12-f682-4f41-821d-72480ce9c836","added_by":"auto","created_at":"2025-09-09 20:26:04","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":171655,"visible":true,"origin":"","legend":"\u003cp\u003ecomparison of impedance values of self-madeAg/AgCl electrode and commercial Ag/AgCl cardiac electrode\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7462900/v1/3e3cc81b462e9da00d6d2084.jpg"},{"id":90945935,"identity":"2e5c2da0-e517-4e84-b745-5bdea61b1127","added_by":"auto","created_at":"2025-09-09 20:18:04","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":91262,"visible":true,"origin":"","legend":"\u003cp\u003eECG test diagram (a) fast heart rate: 123 beats/min, (b) slow heart rate: 45 beats/min, (c) normal heart rate: 83 beats/min\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7462900/v1/1d900636f1736146138958a7.jpg"},{"id":91683806,"identity":"2c4da8e3-c023-46f3-895a-40d0fc8a4725","added_by":"auto","created_at":"2025-09-19 07:08:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1647588,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7462900/v1/0db25982-0f04-4c5f-8daa-7cedada182ba.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of Ag/AgCl paste on the performance of screen-printed flexible Ag/AgCl biomedical electrodes","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eWith the continuous development of chemical sensors, biosensors and biomedical electrodes in the fields of health and medical treatment, food and soil quality, climate change and environmental protection, higher requirements are put forward for the corresponding reference electrodes in terms of reliable performance, low cost, designability and flexibility.[\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] Ag/AgCl electrode has the advantages of low polarization, low impedance, simple manufacture and sensitivity to low frequency electric field, which makes it surpass the standard hydrogen electrode and saturated calomel electrode in application scope. Furthermore, with its minimal and stable half-cell potential, the non-polarized Ag/AgCl electrode satisfies the requirements for biomedical electrodes, including good conductivity, robust stability, minimal potential fluctuation, and low polarization potential.[\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] Its widespread use in clinical monitoring and biomedical measurements underscores its significance.[\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] Therefore, Ag/AgCl electrode materials have aroused extensive research interest.\u003c/p\u003e\u003cp\u003eVarious methods exist for preparing Ag/AgCl electrodes, the classical structure of the Ag/AgCl electrode is a glass shell structure, prepared by electrolytic chlorination, which has excellent stability. However, due to the extremely brittle, rigid and bulky structure of traditional glass electricity, its further application is limited.[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] The silver/silver chloride electrode prepared by powder tablet method can be obtained with excellent performance, due to it enhances the close contact and dispersion of Ag/AgCl particles at a certain temperature and pressure. Nevertheless, this method has complicated procedures, high cost and is not easy for mass production.[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] In addition, Ag/Ag electrodes can also be prepared by thermoelectrolysis and other methods,[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] but they can not meet the requirements of flexible, low cost, good flexibility and so on. Transforming Ag and AgCl powder into a low-temperature curable paste for screen printing on a special substrate offers significant advantages.[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] This method boasts flexible design, compact size, simple structure, low cost, excellent repeatability, high consistency, and suitability for industrial production.[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] In biomedicine, this electrode offers significant research value and a vast potential market by meeting the low-cost, customizable, and flexible needs of medical and reference electrodes.[\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThe Ag/AgCl reference electrode requires an internal electrolyte to achieve ideal performance. In order to achieve stable and low-cost Ag/AgCl electrode preparation and make industrial production possible, many researchers mainly focus on the improvement of internal electrolytes. The development of electrolytes such as poly(vinyl acetate) ink containing KCl and paste of sodium alginate containing KCl improved the potential stability and extended the maintenance time effectively.[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] However, in recent years, the preparation of low-cost and disposable Ag/AgCl reference electrodes has aroused great interest among researchers. Therefore, it is also a popular research direction to successfully prepare Ag/AgCl pseudo-reference electrode with stable performance by optimizing printing method, electrode treatment and preparation process.[\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] Among them, Musa et al. developed d a potentiometric system composed of an Ag/AgCl QRE and a pH-electrode (ISM deposited on a graphite electrode) that can be used continuously for a period of not less than 7 days in aqueous solutions. The open-circuit potential measurement performance is that the standard deviation of the open-circuit potential of the electrode is \u0026plusmn;\u0026thinsp;1.2 mV over a period of 7 days, which shows good potential stability. At the same time, an average pH sensitivity of (-60.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7) mV/pH per pH unit is achieved in the pH range of 7.00\u0026thinsp;~\u0026thinsp;7.63.[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] Interestingly, Silva et al. fabricated an ink-jet printed solid-state Ag/AgCl pseudo-reference electrode on PET or chromatographic paper substrates. A silver nanoparticle paste with 20wt% ethylene glycol was applied onto PET or paper substrates using a printing machine. Following curing, the printed silver layer was briefly immersed in a 40 mg/mL NaClO solution to create a silver chloride layer. This preparation technique is suitable for mass-producing solid Ag/AgCl pseudo-reference electrodes in various structures and sizes. The open-circuit potential of the prepared Ag/AgCl pseudo-reference electrode closely matched that of commercial counterparts. The Ag/AgCl pseudo-reference electrode demonstrated excellent reproducibility and stability within 30 minutes, with no significant change observed after 30 days of dark storage.[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eWith the development of biomedical electrodes, higher requirements are put forward for the potential and impedance of Ag/AgCl reference electrodes. As an important part of the reference electrodes, Ag/AgCl pastes seriously affect electrical properties of reference electrode, but there are almost no relevant studies on Ag/AgCl pastes. Consequently, This paper investigates how the specific surface area of Ag powder and the Ag:AgCl ratio affect the resistivity of paste, hydration reaction, long-term stability and electrode potential of Ag/AgCl electrodes. Finally, this paper compares the practical application of self-made and commercial Ag/AgCl reference electrodes in impedance testing and obtains a satisfactory result, at the same time, it is confirmed by Electrocardiogram(ECG) testing that the self-made Ag/AgCl electrode meets the requirements of ECG test. This makes it possible to commercialize the self-made Ag/AgCl electrode in this study, and this paper also provides theoretical reference for the development of Ag/AgCl electrode.\u003c/p\u003e"},{"header":"2. Experiment","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials and experimental equipment\u003c/h2\u003e\u003cp\u003eThis study utilized the following chemicals: low diameter/thickness ratio flaky Ag powder L (specific surface area: 0.57 m\u003csup\u003e2\u003c/sup\u003e/g, from Sino-Platinum Metals Co., Ltd.), high diameter/thickness ratio flaky Ag powder H (specific surface area: 1.24 m\u003csup\u003e2\u003c/sup\u003e/g, from Sino-Platinum Metals Co., Ltd.), NaCl (\u0026ge;\u0026thinsp;99.5%, from Sinopharm Chemical Reagent Co., Ltd.), AgNO\u003csub\u003e3\u003c/sub\u003e (\u0026ge;\u0026thinsp;99.8%, from Sinopharm Chemical Reagent Co., Ltd.), and modified bisphenol A epoxy (from Sino-Platinum Metals Co., Ltd.).\u003c/p\u003e\u003cp\u003eThree-roll grinder (MTR-50EP, WINNER) is used for Ag/AgCl pastes rolling, high-resolution screen printing machine(TY-CP6090B, CHNTOP) is used for electrode printing, cold-field emission scanning electron microscope (SU8010, HITACHI) is used for electrode micro-morphology observation, electrochemical workstation (600E, CH Instruments) is used for electrode potential and cyclic voltammetric curve testing, impedance analyzer (E4990A, KEYSIGHT) is used for impedance testing, and the ECG detection system is used for ECG testing.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Preparation of AgCl powder\u003c/h2\u003e\u003cp\u003eA 0.02 mol/L AgNO\u003csub\u003e3\u003c/sub\u003e solution was gradually added to an excess 0.02 mol/L NaCl solution, with continuous stirring, to form an AgCl suspension. Following repeated centrifugation and washing, excess chloride ions were removed until the supernatant showed no turbidity upon titration with AgNO\u003csub\u003e3\u003c/sub\u003e solution. The sediment was then washed three times with alcohol through centrifugation and subsequently placed in a constant-temperature drying oven. AgCl powder was prepared by drying at 70\u0026deg;C for 6 hours. Since AgCl is easily decomposed under visible light, the whole preparation process must be carried out in a dark room or under dark conditions.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Preparation of Ag/AgCl pastes\u003c/h2\u003e\u003cp\u003ePrepared AgCl powder, flaky Ag powder, and modified bisphenol A epoxy were mixed in the agate mortar according to a specific ratio. Subsequently, a three-roll mill is used for secondary mixing and rolling until the fineness is reduced to less than 10\u0026micro;m, at which point the Ag/AgCl paste was ready. The mass ratio of Ag/AgCl powder to resin used in this paper was 3:2. Two types of silver powder were used: flaky Ag powder L with low diameter-thickness ratio and flaky Ag powder H with high diameter-thickness ratio. The microstructure of different types of silver powders is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Two types of flaky Ag powder and AgCl powder were combined into 10 paste groups based on various mass ratios: (L1, H1) Ag:AgCl\u0026thinsp;=\u0026thinsp;7:3, (L2, H2) Ag:AgCl\u0026thinsp;=\u0026thinsp;6:4, (L3, H3) Ag:AgCl\u0026thinsp;=\u0026thinsp;5:5, (L4, H4) Ag:AgCl\u0026thinsp;=\u0026thinsp;4:6, and (L5, H5) Ag:AgCl\u0026thinsp;=\u0026thinsp;3:7.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Ag/AgCl electrode design\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the structure diagram of the Ag/AgCl electrode. The preparation process is as follows: firstly, self-made silver paste with low temperature and high conductivity is printed on PET film. This was followed by oven curing at 150\u0026deg;C for 15 minutes to form the base silver electrode. Subsequently, the Ag/AgCl paste was printed onto the silver electrode and oven-cured at 150\u0026deg;C for 15 minutes to solidify the Ag/AgCl electrode layer. Finally, a protective isolation resin was applied to the center of the electrode assembly.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Conductivity characterization of Ag/AgCl paste\u003c/h2\u003e\u003cp\u003eTen groups of Ag/AgCl electrode pastes were printed onto PET film, with ten samples in each group. Following curing, a multifunctional four-point probe tester was used to measure the sheet resistance of the Ag/AgCl electrodes. Subsequently, the thickness of the Ag/AgCl electrodes was determined using a film thickness gauge, allowing for the calculation of their resistivity.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Electrochemical characterization of Ag / AgCl electrode\u003c/h2\u003e\u003cp\u003eThe self-made Ag/AgCl electrode served as the working electrode, with a commercial saturated potassium chloride Ag/AgCl reference electrode and a platinum auxiliary electrode comprising the three-electrode system. Electrochemical workstations were used to characterize the electrode potential stability, hydration period, cyclic voltammetry, and consistency across different solution environments.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.7. Impedance test of Ag/AgCl electrode\u003c/h2\u003e\u003cp\u003eThe impedance of the self-made Ag/AgCl electrode was measured with an impedance analyzer, using a hydrogel layer between two identical electrodes as the sample, and then compared to the impedance of a commercial Ag/AgCl electrode.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e2.8. Ag/AgCl electrode ECG test\u003c/h2\u003e\u003cp\u003eThrough electrochemical and impedance tests, the sample with the best performance is selected and ECG test was observed by ECG detection system.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.1. The effect of different Ag powder and Ag:AgCl ratio on the conductivity of Ag/AgCl pastes\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e displays the resistivity test results for ten groups of Ag/AgCl pastes. Note: The resistance of Ag/AgCl pastes with a 3:7 Ag powder L ratio exceeded the equipment's range, and thus resistivity was not measured. According to the table, for Ag powder H, resistivity increases rapidly when the Ag:AgCl ratio is below 4:6. Similarly, for Ag powder L, resistivity surges when the ratio is below 5:5. Beyond a specific Ag:AgCl ratio, the increase in resistivity becomes negligible.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eResistivity test results of silver/silver chloride pastes\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eAg:AgCl\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u003cp\u003eHigh diameter/thickness ratio flaky Ag powder H\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e\u003cp\u003eLower diameter/thickness ratio flaky Ag powder L\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAg/AgCl pastes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eResistivity\u003c/p\u003e\u003cp\u003e(Ω\u0026middot;m)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eStandard error\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eAg/AgCl pastes\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eResistivity\u003c/p\u003e\u003cp\u003e(Ω\u0026middot;m)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eStandard error\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7:3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.63E-07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.027\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eL1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.77E-07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.029\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6:4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.87E-07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.032\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eL2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.42E-07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.025\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5:5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.16E-07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.035\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eL3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5.97E-06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.043\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4:6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.15E-06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.048\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eL4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.76E-02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.272\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3:7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.24E-03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.327\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eL5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents SEM images of the Ag/AgCl electrode's surface morphology. Electron beam irradiation was used to remove the resin layer and expose AgCl particles, as they are wrapped underneath it in the Ag/AgCl electrode. Consequently, resin removal was incomplete in some images, allowing only partial observation of AgCl areas. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a) and (b) show that nano-AgCl particles are dispersed on the flaky silver powder surface without forming agglomerates upon solidification of the L2 and H2 Ag/AgCl pastes. Despite the identical Ag:AgCl ratios in H2 and L2 pastes, the larger specific surface area of Ag powder H results in fewer nano-AgCl particles on its surface. These particles tend to preferentially accumulate at the edges of flaky Ag powder with high surface energy.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c) and (d) reveal that nano-AgCl particles are uniformly distributed on flaky Ag powder H's surface after H3 pastes solidify, with fewer particles near the interfaces where flakes contact. Consequently, this distribution minimally affects the conductive contacts between flaky silver powders. This observation aligns with the phenomenon where the Ag:AgCl ratio in H3 pastes decreases slightly, yet there's a minor increase in paste resistivity. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(e) and (f) show that after L3 and H4 pastes solidify, nano-AgCl particles on the flaky Ag powder surface begin to cluster together. The resulting AgCl layer on the flaky Ag powder surface thickens, leading to an increase in electrode resistivity. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(g) and (h) illustrate that after L4 and H5 pastes solidify, AgCl particles agglomerate into non-conductive clusters, disrupting flaky Ag powder contact and impeding conductive network formation, thus sharply increasing resistivity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe observed phenomena may result from the lower Ag/Ag interface energy within silver powder mixtures compared to the AgCl/silver and AgCl/AgCl interfaces, and a lower Ag/resin interface energy compared to AgCl powder and resin. At low AgCl powder concentrations, nanoparticles preferentially adsorb on non-contacting surfaces of flaky silver powders. As AgCl powder content increases and nanoparticles fully cover flaky silver powder surfaces, further AgCl nanoparticles cannot form additional Ag-AgCl interfaces. Instead, they tend to form AgCl-AgCl interfaces, causing Ag/AgCl particles to aggregate rather than disperse uniformly in the resin. Increased AgCl agglomeration disrupts contact among flaky silver powders, destroying electrical conduction paths within the electrode and raising resistivity. The larger specific surface area of silver powder H than L allows for more Ag-AgCl interfaces, necessitating a higher proportion of AgCl to increase the Ag/AgCl electrode's resistivity.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.2 The influence of silver powder and its proportion on the electrochemical characteristics of Ag/AgCl electrode\u003c/h2\u003e\u003cp\u003eBased on the research findings, pastes H1-H4 (with lower resistivity) and L1-L3 were used to prepare Ag/AgCl electrodes He1-He4 and Le1-Le3, respectively, using the method described in section \u003cspan refid=\"Sec6\" class=\"InternalRef\"\u003e2.4\u003c/span\u003e. A three-electrode system was established with the self-made Ag/AgCl electrodes as the working electrodes, commercial Ag/AgCl electrodes as reference electrodes, and platinum electrodes as auxiliary electrodes. The electrode potential stability, hydration period, and cyclic voltammetry curves of the working electrodes in various solutions were measured.\u003c/p\u003e\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\u003ch2\u003e3.2.1 Open circuit voltage test\u003c/h2\u003e\u003cp\u003eThe Ag/AgCl electrode's sensitivity to chloride ion concentrations significantly impacts its performance in various environments. The open circuit voltage of the self-made Ag/AgCl electrode was evaluated using a 0.9% NaCl solution to simulate the sweat environment of the human body. Upon contact with the solution, two equilibrium reactions take place on the surface of the Ag/AgCl electrode, as described below:\u003c/p\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Ag}}_{\\text{(aq)}}^{+}+{\\text{e}}^{-}\\leftrightharpoons\\:{\\text{Ag}}_{\\text{(}\\text{s}\\text{)}}\\)\u003c/span\u003e\u003c/span\u003e 3\u0026thinsp;\u0026minus;\u0026thinsp;1\u003c/p\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{AgCl}}_{\\text{(aq)}}^{+}+{\\text{Cl}}_{\\text{(aq)}}^{-}\\leftrightharpoons\\:{\\text{AgCl}}_{\\text{(s)}}\\)\u003c/span\u003e\u003c/span\u003e 3\u0026thinsp;\u0026minus;\u0026thinsp;2\u003c/p\u003e\u003cp\u003eThe electrode potential of Ag/AgCl satisfies the Nernst equation:\u003c/p\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{E}}_{\\text{(}{\\text{Ag}}^{+}\\text{/Ag)}}={\\text{E}}_{\\text{(}{\\text{Ag}}^{\\text{+}}\\text{/Ag)}}^{0}-\\frac{\\text{RT}}{\\text{nF}}\\text{ln}\\text{([}{\\text{Ag}}^{\\text{+}}\\text{])}\\)\u003c/span\u003e\u003c/span\u003e 3\u0026ndash;3\u003c/p\u003e\u003cp\u003eWhere E\u003csup\u003e0\u003c/sup\u003e represents the standard electrode potential (V), n denotes the number of electrons involved in the electrochemical reaction, R is the gas constant (J K-1 mol-1), T stands for the absolute temperature (K), and F is the Faraday constant (C mol-1). The concentration of free Ag\u0026thinsp;+\u0026thinsp;ions is expressed in mol/L.\u003c/p\u003e\u003cp\u003eGiven that the solubility product of AgCl in aqueous solution remains constant, the theoretical electrode potentials of AgCl can be calculated by input of different concentrations of chloride ions. In a 0.9% NaCl solution, the chloride ion concentration is 0.1540 mol/L, and the corresponding theoretical electrode potential of Ag/AgCl is 0.2704 V at room temperature. At room temperature, the chloride ion concentration in a saturated potassium chloride solution is 3.4030 mol/L, and the corresponding theoretical electrode potential of Ag/AgCl is 0.1908 V. Consequently, the saturated Ag/AgCl electrode serves as the reference electrode for determining Ag/AgCl, with the theoretical open-circuit voltage in a 0.9% NaCl solution estimated at 0.0796 V. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e displays the open-circuit voltage test results for Ag/AgCl electrodes He1-He4 and Le1-Le3.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the open circuit voltage of the He2-He4 and Le2-Le3 groups of electrodes is very close to the theoretical voltage of 0.0796V, with deviations under 3 mV. The hydration cycle of He series electrodes is shorter than that of Le series electrodes, likely due to the resin layer's thickness on the electrode's surface. Thinner resin layers allow for quicker equilibrium of electrode potential. Additionally, the larger specific surface area of silver powder H results in a thinner resin layer than that on electrodes using silver powder L, thereby shortening the He group's hydration period relative to the Le group. Comparatively, within each group, electrodes with lower AgCl content exhibit shorter hydration periods than those with higher AgCl content, likely due to the different amounts of chloride ions required to achieve equilibrium. Regarding hydration period, the three groups of Ag/AgCl electrodes, He2-He4, demonstrate satisfactory performance. In terms of long-term stability, the open-circuit voltage changes for electrodes in groups He3 and Le3 were below 1 mV within 24 hours of reaching stability.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\u003ch2\u003e3.2.2 Cyclic voltammetry test\u003c/h2\u003e\u003cp\u003eThe redox reversibility of the self-made Ag/AgCl electrode was evaluated using cyclic voltammetry in a saturated potassium chloride solution. Electrochemical workstation parameters were configured with a high potential of 0.8 V, a low potential of -0.8 V, a scanning rate of 0.05 V/s, one scanning cycle, a sampling interval of 0.001 V, and a sensitivity of 0.01 A/V. The experimental results are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. Except for the the He4 electrode, the oxidation and reduction peaks for the four electrode groups are nearly symmetrical, and the He3 electrode is the best. This indicates good redox reversibility across these groups.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eCombining the test results of open circuit voltage and cyclic voltammetry, electrodes composed of sheet silver powder H with an Ag:AgCl ratio of 5:5 demonstrate better overall performance. They feature a short hydration period, stable open-circuit voltage, and reversible redox reactions.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.3 impedance test\u003c/h2\u003e\u003cp\u003eImpedance variations for the five self-made electrode groups (He2-He4, Le2-Le3) and commercial Ag/AgCl cardiac electrodes from Shanghai Junkang Medical Equipment Co., Ltd., across a frequency range of 20-10000 Hz, were assessed using the method outlined in section \u003cspan refid=\"Sec9\" class=\"InternalRef\"\u003e2.7\u003c/span\u003e. Results are depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The five self-made Ag/AgCl electrodes demonstrated lower impedance values compared to the commercial electrode. This may be due to the fact that commercial electrodes are coated with thin AgCl layers on Ag, forming a double-layer structure with a single Ag-AgCl interface. Conversely, the self-made Ag/AgCl pastes ensure a uniform dispersion of AgCl particles on silver powder, yielding a greater number of Ag-AgCl interfaces, resulting in more Ag-AgCl interfaces, thus making the AgCl layer thinner, which stabilizes the electrode structure, enhances electrical conductivity, and reduces impedance. Furthermore, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows that the impedance of the Ag/AgCl electrode using the same silver powder increases with increasing AgCl content. This change is particularly pronounced in the frequencies between 0-5000 Hz. However, from 5000\u0026ndash;10000 Hz, the impedance disparity diminishes, and impedance overall declines as frequency increases.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e3.4 ECG test validation\u003c/h2\u003e\u003cp\u003eThe ECG signal detection capabilities of self-made Ag/AgCl paste electrodes He3 was validated using an ECG detection system. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e displays ECG monitoring results using self-made electrode pastes. As shown in the Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the self-made Ag/AgCl electrode successfully detected ECG signals with clear and complete periodic variations. In group He3, there was minimal noise interference, making the five standard ECG waveforms (P, Q, R, S, T) distinctly visible. The findings indicate that the self-madeHe3 Ag/AgCl electrode is sufficient for medical ECG testing.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this paper, Ag/AgCl paste, which is less studied among Ag/AgCl electrode materials system, is taken as the research point. The effects of silver powder type and silver content on the conductivity and microstructure of Ag/AgCl paste was studied. Nano-AgCl particles were observed to preferentially bind to the surface of flaky silver powder, aggregating and thus impacting the electrode's conductivity. Therefore, the AgCl ratio should be maintained below a certain threshold to prevent a rapid increase in electrode resistivity, flaky silver powder with a larger surface area can accommodate a higher proportion of AgCl.\u003c/p\u003e\u003cp\u003eThrough electrochemical, impedance, and ECG testing, the efficacy of self-made Ag/AgCl electrodes, with silver to silver chloride ratios of 5:5, was confirmed to satisfy ECG testing requirements. The Ag:AgCl\u0026thinsp;=\u0026thinsp;5:5 electrode exhibits superior open circuit voltage stability, enhanced redox reversibility and reduced impedance. In conclusion, self-made Ag/AgCl electrode achieves the most satisfactory performance, and has a good application prospect in the field of ECG testing.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConflict of interest\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThis work was funded by the Major Science and Technology project of Yunnan Province (Grant No. 202402AB080005 and 202102AB080008), the Fundamental Research Project of Yunnan Province (Grant No. 202501AS070110), the Science and Technology projects of Yunnan Precious Metals Laboratory (Grant No. YPML-2023050206, YPML-2022050207 and YPML-20240502102).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eWei Li: Writing \u0026ndash; review \u0026amp; editing, Writing \u0026ndash; original draft, Methodology, Data curation, Formal analysis, Validation, Visualization. Qingyue Luo: Writing \u0026ndash; review \u0026amp; editing, Writing \u0026ndash; original draft, Methodology, Data curation, Formal analysis, Validation, Visualization. Danlei Jing: Writing \u0026ndash; review \u0026amp; editing, Conceptualization, Methodology, Data curation, Investigation. Yongqing Hu: Validation. Hu Sun: Investigation. Xianglei Yu: Resources. Bowen Yang: Data curation. Zikai Xiong: Methodology. Jianqiang Wang: Conceptualization, Methodology, Supervision, Visualization. Junpeng Li: Conceptualization, Supervision, Project administration, Funding acquisition.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData will be made available on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eZ.Wang, M. et al. Development and evaluation of an ultralow-noise sensor system for marine electric field measurements. \u003cem\u003eSens. 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Disposable Miniaturized Screen-Printed pH and Reference Electrodes for Potentiometric Systems. \u003cem\u003eElectroanal\u003c/em\u003e \u003cb\u003e23\u003c/b\u003e (1), 115\u0026ndash;121. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/elan.201000443\u003c/span\u003e\u003cspan address=\"10.1002/elan.201000443\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2011).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ag/AgCl electrode, screen printing, conductivity, ratio of Ag: AgCl, electrocardiogram testing","lastPublishedDoi":"10.21203/rs.3.rs-7462900/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7462900/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Ag/AgCl electrode has been widely used in biomedical electrodes due to its many advantages. In recent years, Ag/AgCl electrode materials prepared by screen printing method have attracted extensive research interest, but the effect of Ag/AgCl paste on the performance of screen-printed flexible Ag/AgCl electrodes has been neglected. In this paper, the effects of different types and contents of silver powder on the conductivity and microstructure of Ag/AgCl paste electrode were studied, to optimize the best type of silver powder and the ratio of Ag: AgCl for paste preparation. The structure of the Ag/AgCl electrode was designed, and the performance of the fabricated Ag/AgCl electrode was evaluated using an electrochemical workstation, an impedance tester, and an electrocardiogram detection system. When flaky silver powder H with high specific surface area is used and the ratio of Ag:AgCl is 5:5, the prepared electrode can meet the requirements of electrocardiogram testing.\u003c/p\u003e","manuscriptTitle":"Effect of Ag/AgCl paste on the performance of screen-printed flexible Ag/AgCl biomedical electrodes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-09 20:17:59","doi":"10.21203/rs.3.rs-7462900/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1bfe2d61-31a0-4180-9bb6-0efeb7ea6f3d","owner":[],"postedDate":"September 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":54360741,"name":"Physical sciences/Chemistry"},{"id":54360742,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2025-09-19T07:08:23+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-09 20:17:59","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7462900","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7462900","identity":"rs-7462900","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}