Reference Electrode Position Research Articles

Investigation of different locations for reference electrodes inside lithium-ion pouch cells

Three-electrode lithium-ion battery cells enable information about internal cell processes and properties. In this paper, the impact of the reference electrode location inside pouch cells with negative electrodes that have a geometrical overhang are analyzed. Reference electrode measurements of commercially available three-electrode coin cells are used as the benchmark for the self made three-electrode pouch cells with a Li4Ti5O12 (LTO) reference electrode. Different designs of three-electrode pouch cells lead to overestimations or underestimations of the electrodes' overpotentials compared to the benchmark. These results lead to a theory about the requirements of an ideal reference electrode position in pouch cells. Based on that, the reference electrode is placed next to the outer edge of the positive electrode, opposite to the negative electrode's overhang area. By means of experiments and 2D simulations it is shown that the insulation of the negative electrode's overhang area is necessary for appropriate measurement fidelity of the electrode potentials. Moreover, the measured electrode potentials are verified by the correlation of lithium-plating with measured negative electrode potentials below 0 V vs. Li/Li+.

A highly sensitive, easy-and-rapidly-fabricable microfluidic electrochemical cell with an enhanced three-dimensional electric field

An NP-μFEC is a reusable, novel microfluidic electrochemical cell with multiple non-planar interdigitated microelectrode arrays, minimal sample volume, and enhanced electric field penetration for highly sensitive electrochemical analysis. (i) The NP-μFEC features spatial 3-electrode architecture, and a small sample volume (∼4 μL). (ii) Here, [Fe(CN)6]3-/4- redox couple are used as an electrochemical reporter. The effects on the electrochemical properties of NP-μFEC due to the change in the reference electrode (RE) and counter electrode (CE)'s position with respect to the working electrode (WE) position are analyzed. For NP-μFEC, the position of the RE with respect to the WE does not affect the CV, DPV electrochemical profiles. However, the spacing between the CE and WE plays a significant role. (iii) The enhanced three-dimensional electric field penetration in NP-μFEC is validated by finite element analysis simulation using COMSOL Multiphysics. (iv) Without electrode surface modifications, NP-μFEC shows a detection limit (DL) of ∼2.54 × 10−6 M for aqueous [Fe(CN)6]3-/4- probe. (v) The DL for Cu2+, Fe3+, and Hg2+ are 30.5±9.5 μg L−1, 181±58.5 μg L−1, and 12.4±1.95 μg L−1, respectively, which meets the US Environmental Protection Agency (EPA)'s water contamination level for Cu, Fe, and is close to that for Hg (EPA limits are 1300 μg L−1, 300 μg L−1, and 2 μg L−1, respectively). (vi) Further, using a pressure-sensitive adhesive layer to form the channel and create the NP-μFEC configuration simplifies the manufacturing process, making it cost-effective and allowing for rapid adoption in any research lab. NP-μFEC is used to detect heavy metal ions in water. This demonstrates that cost-effective, easy-to-fabricate NP-μFEC can be a new sensitive electrochemical platform.

Deconvoluting CO2 Electroreduction Membrane-Electrode-Assembly Performance Via Five-Electrode Setup

For CO2 electrolysis, a zero-gap or membrane-electrode-assembly (MEA) configuration is desirable for lowering internal resistances and enabling the use of dilute supporting electrolytes for operation at industrially relevant current densities (>100 mA cm-2). However, to rationally optimize individual electrolyzer components, the contributions that cell components (cathode, anode, and membrane) have on the total cell voltage and internal resistance need to be deconvoluted. Moreover, deconvolution techniques can provide operando snapshots of electrode dynamics and component potentials to help assess component degradation for accelerated stability testing protocols1.In this work, we present a technique for the complete deconvolution of the cell voltage and internal resistances through a five-electrode setup. Unlike similar methods1-3, three additional reference electrodes are introduced: two quasi-reference electrodes on each side of the MEA and one fritted reference electrode in the supporting electrolyte, fed to the anode, for validation of quasi-reference electrode potentials before and after testing. Furthermore, the technique presented in this work was optimized for ease of implementation for a standard test setup for laboratory-scale CO2 electrolysis without requiring modifications to the electrochemical cell endplates or a multi-channel potentiostat.Using this five-electrode setup, a significant membrane impedance at both high and low frequencies is identified for a CO2 reduction MEA employing an anion exchange membrane. As shown via electrochemical impedance spectroscopy (EIS) (Fig. 1b), the membrane accounts for about 40% of the total cell impedance at high frequencies. Notably, the membrane also exhibits a low-frequency impedance attributed to concentration gradients across the membrane4. As an initial validation check, the individual EIS spectra of each component were summed to obtain the measured full cell EIS spectra, albeit with an introduction of measurement noise (Fig. 1b, d).To further validate the setup, the corners of the cathode and anode electrodes were cut asymmetrically to assess sensitivity towards edge effects from electrode misalignment reported for a similar technique (Fig. 1a,c)2. We demonstrate that the membrane impedance can be reversed by deliberately introducing this edge effect (Fig. 1b,d). In this reversed configuration, the measured membrane impedance is flipped due to the apparent reference electrode positions being swapped. Moreover, in this configuration the user inadvertently measures the cathode and anode through the membrane, thereby convoluting the signal. This is of significant concern for directly measuring the cathode mass transport dynamics measured at low frequency (<100 Hz) as the membrane has its own characteristic low-frequency impedance. We will present these results and discuss the application of this method towards catalyst layer optimization, diagnosing a working CO2 reduction MEA employing a cation exchange membrane and comparing the performance of zero-gap and hot-pressed MEA configurations.References O. Sorsa, J. Nieminen, P. Kauranen, and T. Kallio, J. Electrochem. Soc., 166, F1326–F1336 (2019) https://iopscience.iop.org/article/10.1149/2.0461916jes.R. Zeng, R. C. T. Slade, and J. R. Varcoe, Electrochim. Acta, 56, 607–619 (2010) http://dx.doi.org/10.1016/j.electacta.2010.08.032.D. Salvatore and C. P. Berlinguette, ACS Energy Lett., 5, 215–220 (2020) https://pubs.acs.org/doi/10.1021/acsenergylett.9b02356.A. Kozmai et al., Membranes (Basel)., 11, 1–17 (2021). AcknowledgementThis work was supported by the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy under award no. DE-EE0009287.0001 Figure 1

Characterization of Electrodes to Record Neural Signals in the Periphery

Appropriately designed electrodes to make in vivo recordings of neural activity have been essential to understanding the nervous system. Recording electrode design has been extensively explored for use in measurement of naturally occurring neural activity in the brain. Recently, recordings of evoked compound action potentials (ECAPs) in the periphery have garnered interest due to their relevance in neuromodulation therapies for determining target engagement and enabling closed‐loop operation. Here, we compare three types of recording electrodes – microelectrodes, cuff electrodes, and intrafascicular electrodes – and their ability to make in vivo recordings of electrically ECAPs, naturally occurring neural activity, and sensory evoked neural activity in the peripheral nerves of a human‐relevant large animal model.The great auricular nerve, innervating the auricle, and cervical vagus nerve of domestic pigs were instrumented with the three recording electrodes. Naturally occurring neural activity, sensory evoked neural activity induced by gentle brushing of the auricle, and electrically ECAPs initiated by non‐invasive and invasive stimulation electrodes were recorded. The study was pre‐registered (https://osf.io/y9k6j).We showed that the recording cuff had superior performance in measuring invasive electrically ECAPs (p &lt; 0.05) while the tungsten microelectrode, routinely used for microneurography in humans, had superior performance in measuring naturally occurring action potentials (p &lt; 0.05). The microelectrode was still able to record electrically ECAPs. Further, we show how choice of reference electrode position may be optimized per application.Microneurography recordings paired with the deployment of a non‐invasive neuromodulation therapy can be used to functionally map sensory innervation areas in patients, allowing individualized placement of stimulation electrodes to achieve on‐target neural fiber activation. These findings provide a basis to select recording electrode type and configuration for measurement of neural signals in the development and deployment of neuromodulation therapies.

The Impact of Size and Position of Reference Electrode on the Localization of Biphasic Electrotactile Stimulation on the Fingertips.

Development of haptic interfaces to enrich augmented and virtual reality with the sense of touch is the next frontier for technological advancement of these systems. Among available technologies, electrotactile stimulation enables design of high-density interfaces that can provide natural-like sensation of touch in interaction with virtual objects. The present study investigates the human perception of electrotactile sensations on fingertips, focusing on the sensation localization in function of the size and position of reference electrode. Ten healthy subjects participated in the study, with the task to mark the sensations elicited by stimulating the index fingertip using an 8-pad electrode. The test systematically explored several configurations of the active (position) and reference (position and size) electrode pads. The results indicated that there was a spreading of perceived sensations across the fingertip, but that they were mostly localized below the active pad. The position and size of the reference electrode were shown to affect the location of the perceived sensations, which can potentially be exploited as an additional parameter to modulate the feedback. The present study demonstrates that the fingertip is a promising target for the delivery of high-resolution feedback.

Proximal fibular nerve conduction studies to tibialis anterior: Optimal E2 (reference electrode) placement.

Several E2 (reference electrode) positions are described for fibular (peroneal) nerve conduction studies to tibialis anterior (TA). This study compared the contribution of different E2 sites to the TA motor response, using remote referential recordings and different bipolar montages. The medial knee contributes minimal electrical activity to the bipolar TA recordings, whereas tibial, ankle, and toe references resulted in very similar, moderate amplitude contributions consistent with far field potentials. These observations were very similar in controls and in patients with lower leg symptoms and signs. Standard montages using distal leg or foot E2 sites result in lower amplitudes with distortion arising from the E2 electrode, compared with the TA-Knee montage. Optimal measurement of the TA motor response is achieved using a medial knee reference, without compromising measures of fibular nerve conduction across the knee.

In-Situ GI-XRD of Electrochemically Formed Thin Gold-Oxide Layers

In-situ XRD analysis is a valuable tool to maximize understanding of complex (electro-)chemical reactions while eliminating errors or changes in the structure when instable compounds or materials that react with air are analysed ex-situ. Surface analysis has been a key aspect in the basic research of metal corrosion. Nevertheless, there is more work to be done to achieve complete understanding which is in part because of the lack of proper in-situ analyses. Unfortunately, previous setups for in-situ XRD analysis come along with their own set of problems. In these constructions a low signal/noise ratio can be seen as the beam has to penetrate the electrolyte. High energy synchrotron radiation and long exposure is needed to get information of surface reactions which makes it very laborous and hard to get high quality data. Various researchers like M. Fleischmann et al [1] introduced new XRD cells in which electrolyte layer thickness was minimized to reduce the energy loss and get more accurate XRD information. However, due to issues with current density distribution and other restrictions like depletion of electroactive species or unfavorable reference electrode position electrochemical processes with high reaction rates cannot be investigated accurately in this setup.In a new setup S. Reither et al [2] introduced a XRD cell where copper is sputtered on a XRD-transmittable polyimide foil as a working electrode. The XRD beam is directed through the polyimide and the thin metal film where the reaction happens without passing the electrolyte underneath. A normal electrochemical cell can be used at the side of the working electrode with inlets for counter- and reference electrode. Depending on the reaction rate the setup also includes an in- and outlet to circulate electrolyte if required. Gracing incidence XRD geometry allows for improvement of the signal intensity of thin-film surface reactions.To demonstrate the strength of the setup the oxidation of polycrystalline gold was investigated. Gold is used as the surface reactions are unique compared to other metals due to its stability against oxide formation. L D Burke et al [3] have tried to investigate the reactions taking place at high voltages to create monolayers and thick oxide layers under different conditions. While normal metal oxidation occurs at the surface, gold oxidation occurs beneath a monolayer of adsorbed hydroxy-ions and is catalysed by repulsion triggered ion exchanges at the surface, increasing the influence of conditions and reaction time as well as the current. Our goal is to use the novel in-situ-XRD system to better understand how gold behaves in various electrolytes using both cyclic and constant voltages to create oxide films. It is suspected that gold oxides have porous or amorphous structure. Therefore, a direct XRD-analysis might be difficult. On the other hand, the correlation of electrochemical data with XRD-data allows the indirect categorization between amorphous and crystalline phases at different conditions as pH and temperature.The details of the in-situ XRD-cell as well as its contribution to analysing gold oxide are presented in this contribution.Image explanation:1 .. counter electrode2 .. polymer window with working electrode3 .. reference electrode4, 5 .. solution in- and outlet[1] M. Fleischmann, A. Oliver, and J. Robinson, ‘In Situ X-ray diffraction studies ofelectrode solution interfaces’, Electrochimica Acta, vol. 31, no. 8, pp. 899–906, (1986)[2] S. Reither, W. Artner, A. Eder, S. Larisegger, M. Nelhiebel, C. Eisenmenger-Sittner, G.Fafilek, ‘On the In-Situ Grazing Incidence X-Ray Diffraction of Electrochemically FormedThin Films’, ECS Transactions, 80 (10) 1231-1238, (2017) 10.1149/08010.1231ecst[3] L.D. Burke and P.E Nugent, Electrochim. Acta, 42, 399, (1997) Figure 1

Influence of reference electrode position on the compound muscle action potential

ObjectiveWhen the compound muscle action potential (CMAP) is recorded in motor nerve conduction studies, the reference (E2) electrode can make a significant contribution to the CMAP. This study investigates the E2 recorded signal and its effect on CMAP measurements when E2 electrode is placed at different sites. MethodsThe CMAP was recorded using the active electrode on the muscle belly and 4 different E2 electrodes placed at distal and proximal sites. The signal recorded by each electrode was also measured using a reference electrode on the contralateral limb. Signals were recorded from the abductor pollicis brevis, abductor digiti minimi, tibialis anterior and biceps muscles. ResultsThe E2 recorded a smaller signal when it was placed near or off the proximal tendon or muscle origin. This affected CMAP latency, duration for tibialis anterior. Contrary to expectation, initial upward deflection was noted for E2 signal. ConclusionA proximal E2 position records a lower volume conducted signal and yields a CMAP that is more representative of the muscle over which the E1 (active) electrode is placed. SignificanceThe proposed ‘Proximal E2’ montage may be better suited to assess pathology.

Location of Reference Electrode Does Not Interfere on Electromyographic Parameters in the Domains of Time and Frequency.

There is currently little information on the positioning of reference electrode (RE). It is generally accepted that it must be positioned on electrically neutral tissues, such as tendons or bony prominences. The objective of this study is to analyze the characteristics of the electromyographic signal (EMG) for different positions of RE as well as at different levels of muscle contraction. Signals from the brachial biceps and triceps were recorded from 18 healthy women (BMI: 21.20kg/m2 ± 1.72; mean age: 21.94 ± 1.98years old) during 100 and 50% maximum flexion voluntary isometric contractions, as well as at rest. For each situation, the RE was randomly positioned in 4 different locations: a) homolateral acromion; b) homolateral brachial biceps; c) styloid process of the contralateral ulna; and d) lateral malleolus of the contralateral ankle. For statistical analysis, Shapiro-Wilk and Kruskal-Wallis tests were used, followed by Dunn's post-hoc test, at a significance level of 5% (p < 0.05). RMS, normalized RMS, PSD, median frequency and levels of energy at 60Hz, 120Hz and 180Hz were assessed for the different sites of RE. The results show that the positioning of the RE on the four experimental locations did not change important features of the electromyographic signals in the time and frequency domains, for the three levels of isometric contractions studied. Such findings compel us to re-think the current trend regarding the RE position followed by the great majority of the researches in areas such as physical therapy.

(Invited) Redox Chemistry of Li-Sulfur Batteries Investigated Via Electrochemistry, X-Ray Photoelectron Spectroscopy and Electron Paramagnetic Resonance

With specific energies of 400–500 Wh kg-1 Li-Sulphur (Li-S) batteries are promising candidates for energy storage applications. Challenges that still impede their commercialization are the expansion of the cathode during discharge, low conductivity, operational instability due to side reactions and slow Li+ transport [1]. In the presence of Li+, sulphur undergoes a multistep reduction, yielding Li2S as an end product. Practically, however, the highly reactive and soluble sulphur intermediates (polysulfides) inevitably form and start their activity as a redox shuttle or/and participate in side reactions. These processes follow a complicated mechanism, which clarification requires a comprehensive analysis [1-3]. This paper will discuss recent results from the authors' labs on the multi-electron transfer of sulfur as a function of the electrolyte composition. Additionally, we have investigated the influence of cathode binder type (e.g. Polyvinylidene difluoride-PVDF, Carboxymethylcellulose-CMC, Guar gum - GG) on the cycling performance of the cathodes. Our methodology involves a combination of electrochemical (galvanostatic cycling, cyclic voltammetry, impedance spectroscopy- EIS) and spectroscopic methods (X-ray Photoelectron Spectroscopy, XPS; Electron Paramagnetic Resonance, EPR), useful for analysis of electrolyte and interface stability. We will show that the increase of lithium bis(trifluoromethylsulfonyl)imide (Li[Tf2N]) concentration displays a valuable impact on the cycling stability(Fig1A,B), suppressing the shuttle effect and improving capacity retention of the sulfur-lithium cells. Moreover, the polysaccharide type binders present better cycling performance in terms of capacity retention and current efficiency (Fig1A,B). To understand the origin of this improvement we characterized the chemical composition of the cycled electrodes by means of XPS. Additionally, the role of small amount 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][Tf2N]) was also studied. Fig.1C,D compares the Li1s and S2p experimental core level peaks from three different anode samples. Sulphur displays multicomponent spectra, in which Li2S (S2p3/2~160eV), disulfides (S2p3/2~162eV), sulfites (S2p3/2~167eV) and sulfates (S2p3/2~169eV) can be distinguished [4]. Their comparison reveals difference in the composition on the surface and in the bulk of the passivating layer, when lower concentration of Li[Tf2N] was used, independent on the presence of [BMP][Tf2N] (Spectra 1 and 3). The later however, facilitate the overall decrease of sulphur quantity in the bulk (Spectra 3). Contrary, higher Li[Tf2N] concentration shows nearly identical spectral features before and after sputtering (Spectra 2), suggesting homogeneous in-depth elemental distribution in the interfacial layer. We anticipate that the Li1s core level peaks originate from at least three Li-containing species (Fig.1C), which close proximity in the binding energy scale leads to spectral broadening (FWHM ~3eV, Fig1, Li1s-Panel). The influence of the electrolyte composition on the electrical properties of Li-electrolyte interface was studied by impedance spectroscopy using a symmetric cell [5]. This method allows an individual assessment of the Li|electrolyte interface without interferences from the reference electrode position and the presence of cathode. The properties of the anode interface are correlated with their surface chemical composition, analyzed by XPS. By using EPR we studied the paramagnetic species formed at the early lithiation stage, where typically just long chain polysulfide anions are present. Our studies demonstrate generation of at least one sulphur-centered radical, which suggests that disproportionation accompany the sulfur lithiation reaction [6]. We will discuss the quantity, the life-time and the coordination geometry of the detected radicals.

Placement of Reference Electrode, Electrolyte Thickness and Three-Electrode Cell Configuration in Solid Oxide Fuel Cells: A Brief Review and Update on Experimental Approach

Cell configuration and placement of reference electrode (RE) have been a subject of intensive interests to the solid oxide fuel cells (SOFCs) communities. Here, the relationship between the position of RE, electrolyte thickness, electrode/electrolyte contact and reliability of 3-electrode cell configuration in electrode polarization and resistance separation is briefly reviewed with particular emphasis on the experimental approach. Numerous modelling studies show that distortion to the electrochemical impedance measurement of electrode reactions on thin electrolyte cells is not avoidable due to the misalignment of working and counter electrodes (WE and CE) and the differences in their electrochemical characteristics. This has been verified experimentally that the asymmetric contact at the electrode/electrolyte interface can cause the shift of equipotential line/surface away from the electrolyte region, leading to the significant distortion in the polarization measurements. However, the distortion effect of misalignment on the equipotential line/surface depends strongly on the electrolyte thickness. In the case of SOFCs with model La0.8Sr0.2MnO3 cathode and Ni-yttria-stabilized zirconia (Ni-YSZ) cermet anode, the threshold for YSZ electrolyte thickness with equal partitioning of the cell resistance is ∼250 μm. In conclusion, for reliable and accurate polarization and impedance measurements in electrolyte-supported cells, it is suggested that minimum YSZ electrolyte thickness should be 250 μm for plate cells with electrode areas of ∼10 cm2 and 500 μm for button cells with electrode areas less than 1 cm2 for symmetric 3-electrode cell configurations with RE positioned on the inactive surface of electrolyte.

‘Standard’ versus ‘nose reference’ electrode placement for measuring oVEMPs with air-conducted sound: Test–retest reliability and preliminary patient results

This study compared two electrode placements ('standard' versus 'nose reference' placement) for measuring oVEMPs, elicited by air-conducted 500Hz tone bursts. The test-retest reliability of both positions was evaluated and additionally both electrode placements were applied on a group of vestibular patients. Eighteen healthy volunteers (range of 20-25years) participated in the first part and were retested after one week for evaluation of the test-retest reliability. Eleven patients (range of 41-74years) with a variety of vestibular pathologies were tested once. In the normal group, the nose reference electrode placement resulted in significantly larger peak-to-peak amplitudes (p<0.001), shorter n10 (p=0.001) and p15 (p<0.001) latencies and smaller 95% prediction intervals for the Inter-Ocular Ratio (IOR) ([-68, 68] for the standard position versus [-32, 32] for the nose reference position). Furthermore, an excellent amplitude and IOR test-retest reliability was observed with the nose reference configuration, as shown by the intraclass correlation coefficient (ICC), the coefficient of variation of the method error (CVME) and the minimal detectable differences (MDD). In the patient group, the same significant amplitude difference was found. Moreover, three patients presented with absent oVEMPs when recorded with the standard placement, whereas the nose reference placement could evoke a detectable oVEMP response. This study demonstrated that a nose reference electrode position results in larger oVEMP amplitudes and achieves a better reliability for the most important clinical parameters (amplitude and IOR). Our patient data substantiate the possible clinical benefit of this position, but further systematic patient verification is required. The nose reference electrode position facilitates the detection of generally very small oVEMP responses and shows a high test-retest reliability, showing promising potential for future use in the vestibular clinic.

A multi-command SSVEP-based BCI system based on single flickering frequency half-field steady-state visual stimulation

Steady-state visual evoked potentials (SSVEPs) are widely employed in brain-computer interface (BCI) applications, especially to control machines. However, the use of SSVEPs leads to eye fatigue and causes lower accuracy over the long term, particularly when multi-commands are required. Therefore, this paper proposes a half-field steady-state visual stimulation pattern and paradigm to increase the limited number of commands that can be achieved with existing SSVEP-based BCI methods. Following the theory of vision perception and existing half-field SSVEP-based BCI systems, the new stimulation pattern generates four commands using only one frequency flickering stimulus and has an average classification accuracy of approximately 75%. According to the proposed stimulus pattern, using only one frequency without requiring users to stare directly at the flickering stimulus allows users to easily focus on the system and experience less visual fatigue compared to existing systems. Furthermore, new half-field SSVEP-based BCI systems are proposed, incorporating our proposed feature extraction and decision-making algorithm. Extracting the signal from the occipital area and using a reference electrode position at the parietal area yielded better results compared to the central area. In addition, we recommend using an LED or LCD as the visual stimulus device (at the recommended size), which yielded comparable results to our proposed feature extraction and decision-making algorithm. Finally, an application of the proposed system is demonstrated for real-time television control.

(Invited) Effect of Position of Reference Electrode on Electrochemical Impedance in Laminated Lithium-Ion Rechargeable Batteries

Electrochemical impedance spectroscopy (EIS) is a powerful method to investigate the performance of lithium-ion rechargeable batteries (LIRBs). The three-electrode cell was used for the electrochemial impedance measurement of LIRBs to examine the electrochemical properties of the positive and negative electrodes in LIRBs 1-4). It is important to determine the position of the reference electrode in the LIRBs cell because the measured impedance spectra are affected by the current distribution between positive and negative electrodes. Our group 5) determined the suitable position of the reference electrode for impedance measurements in LIRBs with a three-electrode cell by finite element method (FEM). On the basis of FEM analysis, the effect of the position of the reference electrode on the impedance spectrum was investigated by the measurement of the impedance spectrum of the laminated LIRBs. The condition of reference electrode before and after the impedance mesurement of the laminated LIRBs was discussed with the measured impedance spectrum in the present study.

The Effect of Reference Electrode Position in Cochlear Implants

This study aims to evaluate the increase in power of cochlear implants (CI) as the reference electrode (RE) position changes. Patients in whom it is necessary to use the full power of the device to achieve the desired stimulation levels, this strategy will ensure that stimulation capability is maximized. The variability in RE placement in the temporal bone has a measurable effect on the electrical current, impedance, and power consumption, and if the electrode position has a functional effect on the stimulation intensity. The following three approaches were used: 1) classical circuit analysis, 2) 2-dimensional numerical simulations, and 3) real temporal bone measurements using a purpose-made CI. The three approaches demonstrate a significant decrease in the current intensity and electrical resistance for distances that are closer to the intra-cochlear electrode. The results also demonstrate that to maintain a constant current, shorter distances require 33% less power. Reference electrode position during surgery can make significant differences in CI power consumption and threshold intensity, which allows a more powerful stimulation in complicated patients (i.e., those with otosclerosis). This study presents an attractive perspective to surgeons, as it shows a way to decrease consumption that might result in a longer battery life or more power to be devoted to coding strategy performance.

Suitable Position of Reference Electrode in Three-Electrode Cell for Impedance Measurements in Lithium-Ion Rechargeable Battery Investigated By Finite Element Method

Our group [1] determined the suitable position of the reference electrode for impedance measurements in lithiumion rechargeable batteries (LIRBs) with a three-electrode cell by finite element method (FEM). Electrochemical impedance spectroscopy (EIS) is a powerful method to investigate the performance of batteries [2-7]. It is important to obtain the electrochemical paramters of the positive and negative electrodes in LIRBs. In order to measure the impedance spectra of both electrodes in LIRBs cell, a three-electrode cell is used for the impedace measurement. Although the electrochemical properties of the positive and negative electrodes in LIRBs cell were investigated using the three-electrode cell by EIS [8-11], the position of the reference electrode was yet to be established for the impedance measurement. As the measured impedance spectra are affected by the current distribution between electrodes, it is important to determine the suitable position of the reference electrode in the LIRBs cell. In the present study, we proposed the best position of the reference electrode for measurement of the impedance spectra of the positive and negative electrodes in the LIRB cell by using a three-electrode cell. A symmetrical model for the LIRB cell is used for the FEM simulation. The simulations of the current and potential distributions for both electrodes are performed by FEM. The impedance spectra of both electrodes were also calculated by FEM to discuss the effect of the position of the reference electrode on the current distribution between both electrodes.

Optimization of reference electrode position in a three-electrode cell for impedance measurements in lithium-ion rechargeable battery by finite element method

We determine the proper placement of the reference electrode for impedance measurements in lithium-ion rechargeable batteries with a three-electrode cell. Calculations of the impedance spectra of the positive and negative electrodes and simulations of the current and potential distributions between them are performed using the finite element method. In the simulation, the positive and negative electrodes are symmetrical face to face. Distortions of the loops and artifact inductive loops are observed in the impedance spectra of the positive and negative electrodes when the reference electrode is between or at the edges of the electrodes. These distortions and the diameter of the artifact inductive loops become small when the reference electrode is positioned outside the area between the positive and negative electrodes. Simulations also demonstrate that current from the positive electrode can flow to the reference electrode and then the negative electrode, i.e., part of the reference electrode facing the positive electrode becomes cathode and part of the reference electrode facing the negative electrode becomes anode. Therefore, the dissolution of reference electrode occurs during impedance measurements in a three-electrode cell and the reference electrode should be placed outside of the area between electrodes, where there is no potential modulation and gradient.

Ulnar motor study to first dorsal interosseous: Best reference electrode position and normative data.

Reference electrode position affects nerve conduction study results. This study was undertaken to determine the optimal reference electrode position for ulnar motor recording from the first dorsal interosseous (FDI) muscle and to develop normative data. Fifty-one subjects were tested using reference electrode positions on the thumb, index, and little fingers. Latencies were compared with a needle recording from the FDI. Analysis was performed to determine the surface placement that most closely matched the needle recording latency. A normative database was then derived on 100 healthy subjects. Placing the reference electrode on the thumb yielded results closest to the "gold standard" needle recording latency. The 97th percentile (upper limit of normal) for latency was 4.0 ms. The 3rd percentile values (lower limit of normal) for amplitude were 9.0 mV for men and 9.3 mV for women. The reference position on the thumb yields latencies that most closely approximate needle recording. Normative data are presented.

Reference and counter electrode positions affect electrochemical characterization of bioanodes in different bioelectrochemical systems.

The placement of the reference electrode (RE) in various bioelectrochemical systems is often varied to accommodate different reactor configurations. While the effect of the RE placement is well understood from a strictly electrochemistry perspective, there are impacts on exoelectrogenic biofilms in engineered systems that have not been adequately addressed. Varying distances between the working electrode (WE) and the RE, or the RE and the counter electrode (CE) in microbial fuel cells (MFCs) can alter bioanode characteristics. With well-spaced anode and cathode distances in an MFC, increasing the distance between the RE and anode (WE) altered bioanode cyclic voltammograms (CVs) due to the uncompensated ohmic drop. Electrochemical impedance spectra (EIS) also changed with RE distances, resulting in a calculated increase in anode resistance that varied between 17 and 31 Ω (-0.2 V). While WE potentials could be corrected with ohmic drop compensation during the CV tests, they could not be automatically corrected by the potentiostat in the EIS tests. The electrochemical characteristics of bioanodes were altered by their acclimation to different anode potentials that resulted from varying the distance between the RE and the CE (cathode). These differences were true changes in biofilm characteristics because the CVs were electrochemically independent of conditions resulting from changing CE to RE distances. Placing the RE outside of the current path enabled accurate bioanode characterization using CVs and EIS due to negligible ohmic resistances (0.4 Ω). It is therefore concluded for bioelectrochemical systems that when possible, the RE should be placed outside the current path and near the WE, as this will result in more accurate representation of bioanode characteristics.

SU‐E‐I‐52: Validation of Multi‐Frequency Electrical Impedance Tomography Using Computed Tomography

Purpose:Multi‐frequency EIT has been reported to be a potential tool in distinguishing a tissue anomaly from background. In this study, we investigate the feasibility of acquiring functional information by comparing multi‐frequency EIT images in reference to the structural information from the CT image through fusion.Methods:EIT data was acquired from a slice of winter melon using sixteen electrodes around the phantom, injecting a current of 0.4mA at 100, 66, 24.8 and 9.9 kHz. Differential EIT images were generated by considering different combinations of pair frequencies, one serving as reference data and the other as test data. The experiment was repeated after creating an anomaly in the form of an off‐centered cavity of diameter 4.5 cm inside the melon. All EIT images were reconstructed using Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (EIDORS) package in 2‐D differential imaging mode using one‐step Gaussian Newton minimization solver. CT image of the melon was obtained using a Phillips CT Scanner. A segmented binary mask image was generated based on the reference electrode position and the CT image to define the regions of interest. The region selected by the user was fused with the CT image through logical indexing.Results:Differential images based on the reference and test signal frequencies were reconstructed from EIT data. Result illustrated distinct structural inhomogeneity in seeded region compared to fruit flesh. The seeded region was seen as a higherimpedance region if the test frequency was lower than the base frequency in the differential EIT reconstruction. When the test frequency was higher than the base frequency, the signal experienced less electrical impedance in the seeded region during the EIT data acquisition.Conclusion:Frequency‐based differential EIT imaging can be explored to provide additional functional information along with structural information from CT for identifying different tissues.