Ag-AgCl Electrodes Research Articles

3D-printed Ag–AgCl electrodes for laboratory measurements of self-potential

Abstract. This paper details the design, development, and evaluation of a 3D-printed rechargeable Ag–AgCl electrode to measure self-potential (SP) in laboratory experiments. The challenge was to make a small, cheap, robust, and stable electrode that could be used in a wide range of applications. The new electrodes are shown to offer comparable performance to custom-machined laboratory standards, and the inclusion of 3D printing (fused filament fabrication or FFF and stereolithography or SLA) makes them more versatile and significantly less expensive – of the order of ×40 to ×75 cost reduction – to construct than laboratory standards. The devices are demonstrated in both low-pressure experiments using bead packs and high-pressure experiments using natural rock samples. Designs are included for both male and female connections to laboratory equipment. We report design drawings, practical advice for electrode printing and assembly, and printable 3D design files to facilitate wide uptake.

Fast Ionic Actuators with Silver–Silver Chloride Electrodes and a Mixed Ionic Liquid Electrolyte

Excellent conductivity makes silver (Ag) an attractive electrode and current collector material for a variety of devices, also promising faster soft actuators. However, high reactivity challenges the use of Ag in electrochemical systems, as dendritic growth can create undesired conduction pathways and short‐circuit the oppositely polarized electrodes. The challenge of rapid Ag electrochemical migration is addressed using a mixed mixed‐room temperature ionic liquid (RTIL) system (l‐ethyl‐3‐methylimidazolium bis‐(trifluoromethylsulfonyl)‐imide and trihexyl(tetradecyl)phosphonium chloride) that prevents short‐circuiting by engaging the produced Ag+ ions with Cl− anions. The stability of the system is demonstrated on an ionic actuator using Ag–silver chloride (AgCl) electrodes and a mixed‐RTIL electrolyte. The work demonstrates fast (in 5 s) transfer of a large (0.2 C cm−2) charge to high‐specific‐surface‐area carbon without observable dendritic growth in cycling and good electromechanical performance: 4° s−1 deflection rate at 0.8 V s−1 scan rate. Simple spray‐deposition of the Ag–AgCl electrodes promises scalable and cost‐effective fabrication. The combination of high stability and vast charge capacity encourages the engagement of Ag‐based electrodes for many electrochemical applications involving organic electrolytes also beyond robotics.

Quantitative Detection of Ortho-Aminophenol by Using Modified Reduced Graphene Oxide/Indium Tin Oxide Glass Electrode

In this research work the electrochemical oxidation of ortho-aminophenol (oAP) is studied using modified reduced graphene oxide/indium tin oxide (rGO/ITO) glass electrode in acetonitrile medium, tetrabutyl ammonium perchlorate (TBAP) supporting electrolyte. Cyclic voltammetry (CV) and linear-sweep voltammetry (LSV) techniques were used to study the redox behavior of oAP. The graphene oxide-initiated auto-oxidized 2-aminophenoxazine-3-one is irreversibly reduced by modified rGO/ITO glass electrode at −0.048[Formula: see text]V (versus Ag–AgCl electrode). LSV response shows that the cathodic peak current increases notably compared to that of bare rGO/ITO glass electrode and with the increasing concentration of oAP. The oxidized product of oAP was characterized by UV–Visible and FT-IR spectroscopy. The redox behavior of oAP of modified rGO/ITO glass electrode was compared with the electrochemical behavior of oAP at bare glassy carbon electrode.

Optimization of Test Conditions for Evaluating Hydrogen Embrittlement Susceptibility of High-Strength Steel for Prestressed Concrete Poles

Abstract We optimized the test conditions for evaluating the hydrogen embrittlement susceptibility of High-strength steel used in prestressed concrete. Through experiments, we clarified the effects of an applied potential and ammonium thiocyanate (NH4SCN) concentration on hydrogen content. An applied potential of −1.0 V versus Ag-AgCl Electrode (SSE) and an NH4SCN concentration of 1.0 wt. % were optimal for the test. We also determined the dimensions of the test cell and test temperature. Experiments in which we soaked different lengths of specimens and changed the solution volume to specimen area ratio led us to design a test cell with a soaking length of 15 cm and an inner diameter of 8 cm. A test temperature of 50°C was chosen for acceleration of hydrogen embrittlement.

Acute exposure to the chemotherapy cisplatin has a biphasic effect in cardiac contractility

Cancer and cardiovascular diseases are the main causes of death in Uruguay and developed countries. In clinical practice, there is often the need to administrate chemotherapy with cisplatin (CTP) to patients with cardiovascular comorbidities. The aim of this work is to characterize the possible detrimental effects in cardiac function by the acute exposition to CPT using isolated heart and cardiomyocytes from guinea pigs (Cavia porcellus). All the procedures regarding animal experimentation were performed following approved protocols by the university ethics committee. Isolated hearts were placed in a Langendorff system and perfused with Tyrode 1.8 mM Ca2+ as control medium, or with extracellularly added CPT (0-100 µM). Tension was recorded with a gauge force transducer attached to the papillary muscle and electrical responses were measured with Ag-AgCl electrodes placed in surface extremes near the papillary muscle. Cardiomyocytes were isolated by enzymatic methods. Data were obtained by patch clamp and confocal microscopy with Rhodamine and Fluo dyes sensitive to Ca2+ binding. Non-parametric t tests were used for data comparison. The best fit of Hill's equation to dose-response curves was done using nonlinear regression methods. In isolated hearts, CPT showed a biphasic effect over the development of tension, increasing up to 5-10 µM to decrease at higher concentrations. In isolated cardiomyocytes, Ca2+ currents were stimulated and inhibited by CPT in a similar dose. Confocal microscopy showed an increment and a reduction of relative fluorescence of the calcium-sensitive dyes with CPT as well. Our results suggest that CPT may affect cardiac contraction and automatism upon acute exposure of the heart, presumably by blocking L-type (Cav1.2) calcium channels and interference with molecules involved in maintaining the homeostasis of intracellular Ca2+.

Prototype Development of Myoelectrics Signal-Based Exoskeleton

Diffable is incompleteness or abnormality accompanied by consequences for specific functions. The method used is tapping on the hamstring and hamstring muscles quadriceps to determine the resulting voltage—muscle signal tapping using Electromyograph (EMG) and Ag-AgCl electrodes. Average current-voltage contraction and relaxation are used as threshold values to drive the servo motor. This study indicates the tension when the muscle contracts are in the range of 4 volts while the relaxation time is 0.4 volts. Then it can be concluded that the voltage when the muscle is contracted is more significant than when it is relaxed. Using different tension during contraction and relaxation in normal subjects showed that the different tension could drive the prototype exoskeleton.

Design of Prosthetic Arm Based on Myoelectric Control

Absence of an upper limb leads to severe impairments in everyday life, which can further influence the social and mental state. For these reasons, early developments in cosmetic and body-driven prostheses date some centuries ago, and they have been evolving ever since. Following the end of World War II, rapid developments in technology resulted in powered myoelectric hand prosthetics. A design of prosthetic arm based on myoelectric was created. The design incorporates movement of arm in flexion and extension. The signal was acquired from biceps above the elbow joint using Ag-AgCl electrode. The proposed design contains signal conditioning circuit, microcontroller, motor drivers, and motor as part of the major components to control arm movement. Control algorithm by using a microcontroller is presented.

Aqueous Na-Ion/ K-Ion Battery with Cyano-Bridged MOF Cathode and Bis(pyrazolate)-Bridged MOF Anode

Aqueous Na-ion/ K-ion batteries with organic active material have gained intensive attention in the field of electric energy storage because of their abundant resources. However, the rate capability and cyclability of organic active material are relatively poor because of their low diffusivity and undesired miscibility with aqueous electrolyte. To address these issues, we are committed to using organic active material embedded in metal organic frameworks (MOFs), whose structures are open and robust. In this work, we introduce aqueous Na-ion/ K-ion batteries with a cyano-bridged MOF cathode and a bis(pyrazolate)-bridged MOF anode, which proved to be both adequately alkaline ion-diffusive and immiscible with aqueous electrolyte.Prussian blue-type alkaline metal nickel hexacyanoferrate A2Ni[Fe(CN)6] (ANHCF, A = Na, K), in which redox-active Ni and Fe are bridged by κ2-cyano ligand, was synthesized according to previous reports [1,2], while Zn bis(pyrazolate) MOF (ZnNDI), in which redox-silent Zn are bridged by κ2-bis(pyrazolate) ligand containing redox-active naphthalenetetracarboxylic-diimide (NDI) linker, was obtained by the literature method [3]. Electrochemical measurements were carried out by using a three-electrode half cell and a two-electrode full cell with alkaline metal trifluoromethanesulfonates (ASO3CF3) aqueous electrolyte in the molality of 8 mol/kg, which was the most suitable concentration in terms of ionic conductivities and stability window. Electrode pellet were prepared by mixing active materials, conductive additives (acetylene black) and binder (polytetrafluoroethylene) in a weight ratio of 70:25:5, and then these pellets were sandwiched by titanium mesh as current collector. An Ag-AgCl electrode with saturated KCl and activated carbon were used as reference and counter electrodes, respectively.Figure 1a compares 1st and 2nd charge/discharge curves of Na-ion (blue lines) and K-ion (red lines) cells. In contrast to Na-ion cell, K-ion cell displayed higher voltage and larger reversible capacity, possibly due to the fewer [Fe(CN)6]α - (3 < α < 4) defects in the structure of KNHCF than those in NNHCF. After 400 charge/discharge cycles, the Na-ion cell maintained the capacity more than 96% of that at the initial cycle, while the K-ion cell was only 69%, as shown in Figure 1b. These differences may arise from the electrochemical stability of water molecule in the electrolyte, provided hydration number of K-ion is lower than that of Na-ion and hence the number of free water molecules in K-ion electrolyte is higher.AcknowledgementThis work was supported by Element Strategy Initiative of MEXT, Grant Number JPMXP0112101003.

Low-Resistance silver bromide electrodes for recording fast ion channel kinetics under voltage clamp conditions

BackgroundTwo-electrode voltage clamp is a widely used technique for studying ionic currents. However, fast activation kinetics of ion channels are disguised by the capacitive transient during voltage clamp of Xenopus oocytes. The limiting factors of clamp performance include, but are not limited to, amplifier gain, membrane capacitance, and micropipette resistance. Previous work has focused on increasing amplifier gain (e.g.; high performing two-electrode amplifiers) or reducing the membrane capacitance (e.g.; the cut-open technique). New methodThe use of an Ag-AgBr electrode with saturated KBr solution to reduce micropipette resistance. ResultsThe conductivity of 4 M KBr was 37 % higher compared to 3 M KCl and the micropipette resistance was reduced by 19 % when 4 M KBr was used, compared to the standard 3 M KCl solution. Micropipette resistances correlated positively with capacitive transient durations. Neither the current-voltage relationship of the voltage-gated sodium channel, Nav1.7, nor Xenopus oocyte stability were affected by bromide ions. Comparison with existing methodsThe de facto standard for two-electrode voltage clamp is 3 M KCl and Ag-AgCl electrodes, which are associated an unnecessarily high micropipette resistance. Elsewise, cut-open voltage clamp techniques are technically demanding and require manipulation of the intracellular environment. ConclusionsThe use of an Ag-AgBr electrode with saturated KBr as micropipette solution reduces the capacitive transient in two-electrode voltage clamp recordings. Moreover, the exchange of chloride against bromide ions does not seem to affect oocyte physiology and ion channel kinetics.

Multimodal sensor to measure the concurrent electrical and mechanical activity of muscles for controlling a hand prosthesis

A wearable sensor was fabricated to provide simultaneous electromyography (EMG) and force myography (FMG) information, from the same muscle location for controlling multi-functional hand prosthesis. The typical mechanical arrangement of the sensor constitutes silver electrodes and a force-sensitive resistor embedded inside the sensor chassis for detecting the electrical and mechanical activity of muscles. The sensor incorporates specific conditioning units for producing quantifiable EMG and FMG outputs from electrodes and force-sensitive resistor. The sensor exhibited excellent sensitivity and repeatability characteristics in recording force signals. The dry electrodes used in the sensor showed a comparable electrode-skin impedance with conventional Ag-AgCl electrodes. The EMG signals obtained with the sensor for ten subjects showed a good correlation and similar signal-to-noise ratio to signals with a traditional EMG sensor. Further, the nature of the measured EMG and FMG signals for the subjects by the sensor were analyzed by determining features such as signal stability and response time. The simultaneously recorded EMG-FMG signals from the sensor for different muscular contractions can be fused to generate a more reliable control for dexterous operation of hand prosthesis.

A Study on Visual Fatigue and Binocular Visual Function before and after Watching VR Image

Purpose : This study was designed to determine how VR video viewing using HMD devices had an effect on the visual function, EEG, and the visual fatigue. Methods : This study analyzed the 30 subjects(in their 20s to 30s) who used smart devices the most. They had to have no systemic and eye diseases and their corrected vision were 1.0 or higher. The far and near phoria test were repeated three times each using Howell cards(3 m, 40 cm) and 6 Δ prism. The push-up testing to check near point of accommodation and the NPC test were repeated three times. EEG signals were recorded using a Quick cap with 62 Ag-AgCl electrodes and NeuroScan SynAmps. We analyzed the resting EEG data with eyes open and eyes closed using CURRY7, which was commonly used for EEG pre-processing. Results : There were significant differences in near point of convergence(p<0.001), near phoria(p=0.004), and AC/A ratio(p=0.023) after VR image viewing. Accommodation and far phoria were not significant differences. In the brainwave analysis, the relative power of the alpha 1 band(p<0.001) and the relative power of the alpha 2 band(p=0.003) showed the difference in anterior, middle, and posterior. After watching VR images, the simulator sickness questionnaire showed a significant overall difference(p<0.001). In the correlation analysis, alpha 1 band relative power was significantly correlated with near phoria(p=0.038) and AC/A Ratio(p=0.041). Alpha 2 band relative power showed significant correlation with nausea(p=0.029), oculomotor(p=0.021), and disorientation(p=0.010). Conclusion : After watching VR images, NPC significantly increased and exophoria significantly increased in near. And there was a significant increase in the alpha wave. In addition, cyber motion sickness was felt by all subjects, and the degree of disorientation was the biggest increase.

Detection of Heart Abnormalities Using Fuzzy Decision Making and Wireless Transmission of Disease Information

Abstract This research work aims to implement the automatic detection of heart abnormality type without doctor’s assessment using electrocardiogram (ECG) features. First, the ECG signal is acquired via Ag-AgCl electrodes, preprocessed using the adaptive Wiener filter to remove the noises and classified with the help of feature extraction techniques and fuzzy decision making (FDM) algorithm. The FDM also finds the type of heart abnormality based on ECG features, such as RRp interval, R peak amplitude detection, and QRS complex interval, and then sends the classified type to the doctor wirelessly via a ZigBee module. The virtual instrument software has been used to validate the proposed concept, and results of both software and hardware parts have been presented to show the effectiveness of the work.

Development of an enhanced porosity AgAgCl reference electrode with improved stability

We have developed a new low-cost method for fabrication of an enhanced porosity ultra-low noise silver-silver chloride (Ag-AgCl) reference electrode with dramatically high stability, useful in precise electrochemical and biomedical measurements. Low noise level and high stability are the most important features when evaluating reference electrode for example when used as a half-cell at electrochemical cells. The noise was measured for bare Ag-AgCl electrode pairs in a saline electrolyte without any junction. The noise spectral density for such measurements increases at low frequencies due to flicker (1/f) noise. Thermal noise from the real part of the electrode impedance is always lower than 1/f noise and is shown as offset voltage in noise spectrum. Electrode noise is highly correlated to its offset voltage. Moreover, the variance of the potential difference in our measurements is correlated to the noise level of electrodes. In this paper, offset voltage spectrum and the variance of data while doing measurements are proposed for identification of noise in our electrodes. The results presented suggest a new low-cost process for fabrication of enhanced porosity reference electrodes with nanovolt noise level at 1 Hz, low enough for electrochemical and biomedical measurements.

Stability‐indicating analytical method of quantifying spironolactone and canrenone in dermatological formulations and iontophoretic skin permeation experiments

A simple, stability-indicating, chromatographic method of quantifying spironolactone (SPI) and its metabolite, canrenone (CAN), in the presence of excipients typical in dermatological formulations and skin matrices in studies of passive and iontophoretic permeation was proposed and validated here. SPI and CAN were separated using a reversed-phase column with a mobile phase of methanol-water (60:40, v/v) at a flow rate of 1.0 mL/min. Data were collected with a UV detector at 238 and 280 nm, with retention times of 6.2 and 7.9 min for SPI and CAN, respectively. The method was precise, accurate and linear (r2 > 0.99) in a concentration range of 1-30 μg/mL, and recovery rates of SPI and CAN from the different skin layers exceeded 85%. The method was not only sensitive (LOD of 0.05 and 0.375 μg/mL and LOQ of 0.157 and 1.139 μg/mL for SPI and CAN, respectively) but also selective against skin matrices and highly representative components of topical formulations. The method moreover demonstrated SPI's degradation in iontophoresis by applying Pt-AgCl electrodes and its continued drug stability using Ag-AgCl electrodes. Altogether, the method proved valuable for quantifying SPI and CAN and may be applied in developing and controlling the quality of dermatological products.

P12-S Frontotemporal electrode set for ICU bedside cEEG monitoring for comatose patients after cardiac arrest

Background Electroencephalogram (EEG) patterns within 24 h after cardiac arrest (CA) have shown to reliably predict neurological outcome. The recording set-up may be simplified by using a less extensive electrode set. We compared a 4-channel frontotemporal EEG headband (BrainStatus, Bittium, Oulu, Finland) to a 9-channel Ag-AgCl electrode set. Material and methods Between July 2018 and January 2019, EEGs were recorded in 22 consecutive adult patients admitted after CA with both electrode sets simultaneously. EEG patterns were assessed visually, corresponding to the guidelines of the American Clinical Neurophysiology Society (ACNS). Five minute epochs at 24 h after CA were scored by three independent EEG readers blinded to clinical data. Final classification was determined by majority vote. To evaluate classification agreement between the electrode sets, confusion matrices and Cohen’s Kappa were used. Results At 24 h after CA, the background patterns of 21 patients were available. With the 9 electrode set, nine patients had a continuous pattern, two patients had a discontinuous pattern, two patients showed burst-suppression without identical burst, one patient showed burst-suppression with identical bursts, and four patients had a suppressed background pattern. The background pattern of three patients was obscured by artefacts. The agreement for background pattern scoring of the 4 electrode set compared to this 9 electrode set was fair ( κ = 0.32). Conclusions Visual classification of EEG patterns in patients with postanoxic coma with a 9-channel Ag-AgCl electrode set cannot be replaced with a 4-channel frontotemporal EEG headband.

Electrooculogram (EOG) Signal Classification Using Moving Average Technique and its Application to Drive Direct Current Motors

Background: Electrooculogram (EOG) signal is one of the bioelectric signals acquired from the human body to study the movements of eyes and also to design and develop assistive devices. These devices can be mobility devices, video gaming devices or any other assistive device. Methods: Assistive devices are especially designed for quadriplegic or spinal cord injured patients. Motors are one of the key components in the design of mobility devices. These motors are to be driven with the help of EOG commands. This paper explains the process of eliminating involuntary eye movements while driving the motors under the control of EOG signals. The system design is carried out in two ways. Initially the system is designed in such a way that the motors are driven even for involuntary eye movements which is a major drawback of the system. Conclusion: This drawback has been overcome successfully by introducing the moving average technique during classification of the EOG signals. The systems overall classification accuracy is also computed by constructing confusion matrix and has produced high sensitivity, specificity with overall average accuracy of 90.91%. Keywords: EOG, assistive, involuntary, microcontroller, motors, Ag-AgCl electrodes, control signals.

Recording Horizontal Saccade Performances Accurately in Neurological Patients Using Electro-oculogram.

Electro-oculogram (EOG) has been widely used for clinical eye movement recording, especially horizontal saccades, although the video-oculography (VOG) has largely taken the place of it nowadays due to its higher spatial accuracy. However, there are situations in which EOG has clear advantages over VOG, e.g., subjects with narrow eye clefts or having cataract lenses, and patients with movement disorders. The present article shows that if properly implemented, EOG can achieve an accuracy almost as good as VOG with substantial stability for recording, while circumventing problems associated with VOG recording. The present paper describes a practical method for recording horizontal saccades using oculomotor paradigms with high accuracy and stability by EOG in neurological patients. The necessary measures are to use an Ag-AgCl electrode with a wide plastic fringe capable of reducing noise, and to wait for sufficient light adaptation to occur. This waiting period also helps to lower the impedance between the electrodes and the skin, thereby ensuring stable signal recorded as time goes by. Furthermore, re-calibration is performed as needed during the task performance. Using this method, the experimenter can avoid drifts of signals, as well as contamination of artifacts or noise from the electromyogram and electroencephalogram, and can collect sufficient data for clinical evaluation of saccades. Thus when implemented, EOG can still be a method of high practicability that can be widely applied to neurological patients, but may be effective also for studies in normal subjects.

Evaluating the performance of Kalman filter on elbow joint angle prediction based on electromyography

High accuracy in joint angle prediction is very important in the development of devices based on myoelectric control. Joint angle prediction based on a non-pattern recognition method is more preferred due to the robustness and the easiness to adapt to any subject. This paper proposed a new method to predict an elbow joint angle based on electromyography (EMG) which used a time domain feature, zero crossing, and Kalman filter. The EMG signals were collected from biceps muscle using Ag (AgCl) electrodes. To test the proposed method, the subjects were asked to move the elbow in the flexion and extension motion at different periods of motion (12 seconds, 8 seconds and 6 seconds). The EMG features yielded from the feature extraction step were processed using a Kalman filter which was used to predict an elbow joint angle. The performance of the proposed method was evaluated using root mean squared error (RMSE) and the Pearson’s correlation coefficient (CC). In this study, the RMSE and CC values were ranged from 6.9o to 17.5o and 0.93 to 0.99 respectively. The results of the experiment have demonstrated the effectiveness of the proposed method to predict an elbow joint angle based on EMG signal.

Move Your Wheelchair with Your Eyes

Abstract: In the proposed study, our goal is to move paralyzed people with their eyes. Otherwise, use this document as an instruction set. Paper titles should be written in uppercase and lowercase letters, not all uppercase. For this purpose, we use their Electrooculogram (EOG) signals obtained from EOG goggles completely designed by the authors. Through designed EOG goggles, vertical-horizontal eye movements and voluntary blink detection are verified by using 5 Ag-AgCl electrodes located around the eyes. EOG signals utilized to control wheelchair motion by applying signal processing techniques. The main steps of signal processing phase are pre-processing, maximum-minimum value detection and classification, respectively. At first, pre-processing step is used to amplify and smooth EOG signals. In maximum-minimum value detection we obtain maximum and minimum voltage levels of the eye movements. Furthermore, we determine the peak time of blink to distinguish voluntary blinks from involuntary blinks. Finally, at classification step k-Nearest Neighbouring (k-NN) technique is applied to separate eye movement signals from each other. Several computer simulations are performed to show the effectiveness of the proposed EOG based wheelchair control system. According to the results, proposed system can communicate paralyzed people with their wheelchair and by this way they will be able to move by their selves.

Combined characterization of bovine polyhemoglobin microcapsules by UV–Vis absorption spectroscopy and cyclic voltammetry

Polyhemoglobin produced from pure bovine hemoglobin by reaction with PEG bis(N-succynimidil succinate) as a cross-linking agent was encapsulated in gelatin and dehydrated by freeze-drying. Free carboxyhemoglobin and polyhemoglobin microcapsules were characterized by UV-Vis spectroscopy in the absorption range 450-650nm and cyclic voltammetry in the voltage range from -0.8 to 0.6mV to evaluate the ability to break the bond with carbon monoxide and to study the carrier's affinity for oxygen, respectively. SEM used to observe the shape of cross-linked gelatin-polyhemoglobin microparticles showed a regular distribution of globular shapes, with mean size of ~750nm, which was ascribed to gelatin. Atomic absorption spectroscopy was also performed to detect iron presence in microparticles. Cyclic voltammetry using an Ag-AgCl electrode highlighted characteristic peaks at around -0.6mV that were attributed to reversible oxygen bonding with iron in oxy-polyhemoglobin structure. These results suggest this technique as a powerful, direct and alternative method to evaluate the extent of hemoglobin oxygenation.