Electrode Impedance Research Articles

Correlation of residual stress on piezoresistive properties of boron-doped diamond films

To investigate the influence of residual stress on the piezoresistive behavior of boron-doped diamond (BDD) films, BDD films with varying doping concentrations were synthesized using a hot-filament chemical vapor deposition (HFCVD) system on silicon and diamond substrates. The relationship between the surface morphology, structural composition, resistivity, and piezoresistive properties of BDD electrodes was examined, along with an in-depth analysis of the impact of boron doping level on these properties. The microstructure and bonding state of the BDD films were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy. The piezoresistive properties of the BDD films were evaluated employing a cantilever beam bending method. Our findings demonstrate that the level of boron doping not only affects resistivity but also directly influences residual stress in BDD films, both factors having an impact on their piezoresistive properties. Despite significantly larger grain sizes observed in BDD films grown on diamond substrates compared to those grown on silicon substrates at identical boron doping concentrations, they exhibit consistent variations in residual stress and gauge factor (GF) values. With increasing doping levels, the absolute residual stress decreases initially before increasing again; moreover, at 2000 ppm doping level, it transitions from compressive to tensile stress. The GF value is closely associated with both the magnitude and type of residual stress. By utilizing a doping concentration of 2000 ppm for growth on diamond substrates, we achieved a peak GF value of 257 for BDD films which highlights their promising potential for pressure sensor applications.

Concurrent Amorphization and Nanocatalyst Formation in Cu-Substituted Perovskite Oxide Surface: Effects on Oxygen Reduction Reaction at Elevated Temperatures.

The activity and durability of chemical/electrochemical catalysts are significantly influenced by their surface environments, highlighting the importance of thoroughly examining the catalyst surface. Here, Cu-substituted La0.6Sr0.4Co0.2Fe0.8O3-δ is selected, a state-of-the-art material for oxygen reduction reaction (ORR), to explore the real-time evolution of surface morphology and chemistry under a reducing atmosphere at elevated temperatures. Remarkably, in a pioneering observation, it is discovered that the perovskite surface starts to amorphize at an unusually low temperature of approximately 100 °C and multicomponent metal nanocatalysts additionally form on the amorphous surface as the temperature raises to 400 °C. Moreover, this investigation into the stability of the resulting amorphous layer under oxidizing conditions reveals that the amorphous structure can withstand a high-temperature oxidizing atmosphere (≥650 °C) only when it has undergone sufficient reduction for an extended period. Therefore, the coexistence of the active nanocatalysts and defective amorphous surface leads to a nearly 100% enhancement in the electrode resistance for the ORR over 200 h without significant degradation. These observations provide a new catalytic design strategy for using redox-dynamic perovskite oxide host materials.

High protonic resistance of hydrocarbon-based cathodes in PEM fuel cells under low humidity conditions: Origin, implication, and mitigation

Hydrocarbon-based electrodes for proton-exchange membrane fuel cells face challenges in closing the performance gap with electrodes based on perfluorosulfonic acid ionomers, particularly under low humidity conditions. Alongside increased oxygen transport resistance and higher kinetic-induced overpotentials, the protonic resistance of these fluorine-free electrodes is the primary hurdle to improved performance. This study systematically investigates the origin and impact of the cathode protonic resistance on fuel cell performance, utilizing sulfonated phenylated polyphenylenes as hydrocarbon ionomers. Electrochemical characterization at low relative humidity (≤50 %) reveal a high protonic resistance arising from both lower conductivity of the hydrocarbon thin film compared to the bulk membrane and increased cathode tortuosity at a gas transport-optimized ionomer to carbon (I/C) ratio of 0.2. The poor protonic resistance at low relative humidities leads to a non-homogeneous current distribution across the thickness of the cathode electrode, resulting in lower catalyst utilization. To address this issue, reducing the thickness of the cathode CL while maintaining a constant Pt loading (i.e., increasing the Pt on carbon ratio) significantly reduces protonic resistance. This improvement compensates for the kinetic disadvantages of highly loaded carbon particles and results in a considerable performance increase by 40 % at 0.75 V under low relative humidities.

The Local Changes in the Physicochemical Properties during Cu Electrodeposition in an Ionic Liquid Composed of [CuCl2]–

The equimolar mixture of CuCl and 1-butyl-1-methylpyrrolidinium chloride (BMPCl) was found to yield an ionic liquid composed predominantly of BMP+ and [CuCl2]–. Fine deposits of metallic Cu were obtained by potentiostatic reduction of [CuCl2]– in CuCl-BMPCl (50.0-50.0 mol%). The change in the local physicochemical properties near the electrode during the electrodeposition of Cu was analyzed using electrochemical quartz crystal microbalance. The resonance resistance of a quartz crystal electrode increased with an increase in the local viscosity near the electrode, probably reflecting the change in the composition of the electrolyte.

A high-entropy electrode material for electrobiochemical and eletrophysiological signals detection

Electrobiochemical and eletrophysiological signals indicate human physiology, health, and activity performance. It is still a big challenge to detect these biosignals due to the lack of sensing material. Here, we report a high-entropy material for electrobiochemical and eletrophysiological signals sensing. The high-entropy material consists of the conventional transition metallic elements of Fe, Co, Ni, Cu, and Zn. This high-entropy biosignal sensing material is able to detect the concentration of the biomarker of glucose and electrophysiological signals of Electromyography (EMG), Electroencephalography (EEG), Electrocardiography (ECG). The limitation of the glucose detection is 3.3 μM with the sensitivity of 2861 μA mM−1 cm−2. The HEA electrode also presents good linearship to the glucose concentration in PBS. The cell assay and skin assessment results also demonstrate the excellent biocompatibility of this HEA electrode, indicating good feasibility to the real biosamples. The contact impedance of this HEA electrode is lower than the conventional dry electrode, which leads to the good capability in electrophysiological signals detection. This report not only extends the application of high-entropy material in the field of biomedical engineering but also provides a new pathway for electrobiochemical and eletrophysiological signals detection.

High-Performance Red Transparent Quantum Dot Light-Emitting Diodes via Fully Solution-Processed MXene/Ag NWs Top Electrode.

The integration of high-performance transparent top electrodes with the functional layers of transparent quantum dot light-emitting diodes (T-QLEDs) poses a notable challenge. This study presents a composite transparent top electrode composed of MXene and Ag NWs. The composite electrode demonstrates exceptional transparency (84.6% at 620 nm) and low sheet resistance (16.07 Ω sq-1), rendering it suitable for integration into T-QLEDs. The inclusion of MXene nanosheets in the composite electrode serves a dual role: adjusting the work function to enhance electron injection efficiency and enhancing the interface between Ag NWs and the emissive layer, thereby mitigating the common issue of interfacial resistance in conventional transparent electrodes. This strategic amalgamation results in notable improvements in device performance, yielding a maximum current efficiency of 23.12 cd A-1, an external quantum efficiency of 13.98%, and a brightness of 21,015 cd m-2. These performance metrics surpass those achieved by T-LEDs employing pristine Ag NW electrodes. This study offers valuable insights into T-QLED device advancement and provides a promising approach for transparent electrode fabrication in optoelectronic applications.

Development of high performance micro-Resistive Groove detector

The Micro-Resistive Groove (μRGroove) is a single-stage Micro-Pattern Gaseous Detector (MPGD) with a groove amplification pattern. The resistive protection electrode is Diamond-Like Carbon (DLC), ensuring the detector achieves gas gain (≥104) and maintains good stability. The top copper layer of the groove is strip-shaped and can be grounded for 1D-strip readout. Therefore, only an additional 1D-strip is required to achieve 2D spatial resolution. Because the 2D readout is divided on both sides of the amplification structure, the induced charge-sharing effect is avoided, effectively increasing the induced signal amplitude, which is beneficial for applications of large-area tracking and cylindrical MPGD. In this study, we present the design and performance of the 10cm×10cmμRGroove prototype, which can achieve an effective gain of 2×104, an energy resolution of approximately 25%, a maximum detection efficiency close to 98%, and 2D spatial resolution better than 80μm. It also introduces the 50cm×50cm large-area μRGroove, which shows preliminary results with a detection efficiency >96% and 2D spatial resolution better than 100μm, meeting the normal requirements for large-area tracking detection. Finally, it discusses the progress of the low-mass cylindrical μRGroove, with the first prototype having an effective area of 13.1cm in diameter and 10cm in length. Its energy resolution is ∼26% measured by 55Fe and further beam tests being planned. This design is expected to become a practical solution for the inner tracker of the STCF.

Intrathecal placement of percutaneous spinal cord stimulation leads: illustrative cases.

Spinal cord stimulation (SCS), including the percutaneous placement of epidural stimulation leads, has been increasingly utilized to treat chronic pain. Although lead migration is a well-characterized complication, few studies have reported on malpositioned leads in the intrathecal space. Here, the authors discuss two cases of intrathecal lead placement necessitating surgical revision. This report is a two-case series on the inadvertent placement of percutaneous SCS leads in the intrathecal space. The authors describe the identification of malpositioned leads, describe the clinical presentation, characterize stimulation parameters, and report improvement following neurosurgical revision for each case. Two patients originally presenting with chronic low-back pain underwent percutaneous SCS lead implantation. Both patients presented with atypical pain symptoms in the acute to subacute postprocedural period, raising suspicion for malpositioned leads. Imaging was consistent with intrathecal malpositioning. Both patients underwent revision surgery resulting in symptomatic improvement. Indicators of malpositioned thoracic SCS leads in the intrathecal space include thoracoabdominal or flank pain exacerbated by movement, insufficient pain relief versus that in the SCS trial, very low electrode impedances, direct visualization on imaging, and lack of epidural lead visualization following laminectomy. Revision options include removal of the intrathecal leads and the surgical placement of a paddle electrode in the epidural space. https://thejns.org/doi/10.3171/CASE24275.

Minimum intraoperative testing battery for cochlear implantation: the international practice trend.

In cochlear implantation (CI) surgery, there are a wide variety of intraoperative tests available. However, no clear guide exists on which tests must be performed as the minimum intraoperative testing battery. Toward this end, we studied the usage patterns, recommendations, and attitudes of practitioners toward intraoperative testing. This study is a multicentric international survey of tertiary referral CI centers. A survey was developed and administered to a group of CI practitioners (n = 34) including otologists, audiologists and biomedical engineers. Thirty six participants were invited to participate in this study based on a their scientific outputs to the literature on the intraoperative testing in CI field and based on their high load of CI surgeries. Thirty four, from 15 countries have accepted the invitation to participate. The participants were asked to indicate the usage trends, perceived value, influence on decision making and duration of each intraoperative test. They were also asked to indicate which tests they believe should be included in a minimum test battery for routine cases. Thirty-two (94%) experts provided responses. The most frequently recommended tests for a minimum battery were facial nerve monitoring, electrode impedance measurements, and measurements of electrically evoked compound action potentials (ECAPs). The perceived value and influence on surgical decision-making also varied, with high-resolution CT being rated the highest on both measures. Facial nerve monitoring, electrode impedance measurements, and ECAP measurements are currently the core tests of the intraoperative test battery for CI surgery.

Insight into the corrosion inhibition mechanism of mild steel St1 in 2 M H2SO4 electrolyte by azithromycin

Mild steel is essential in modern industry due to its favorable mechanical properties and economic availability. However, its high susceptibility to corrosion, especially in acidic environments, poses a significant challenge, reducing service life, increasing operating costs, and raising the risk of failures. This study investigates the corrosion inhibition mechanism of mild steel St1 in a 2 M H2SO4 solution at various temperatures using the broad-spectrum antibiotic azithromycin (AZM). Experimental results indicate that AZM presence increases the polarization resistance of mild steel in the acidic solution. AZM acts as a mixed-type inhibitor, influencing the kinetics of both cathodic and anodic processes. The introduction of 200 mM AZM leads to an increase in the polarization resistance of the steel electrode in 2 M H2SO4 by up to 2.4 times. The inhibition mechanism involves forming a protective layer of protonated AZM forms on the negatively charged Fe surface. These protonated forms can also adsorb on cathodic areas, competing with hydronium ions (H3O+) and thereby inhibiting hydrogen evolution processes. The protective effect of AZM diminishes with increasing temperature of the corrosive environment, as confirmed by Monte Carlo simulations showing decreased adsorption energies for AZM and its protonated forms at higher temperatures. An assessment of the protective effect of 200 mM AZM showed that an increase in the temperature of the corrosive environment from 293 to 333 K leads to a decrease in the protective effect by almost 5.6 times. Quantum chemical calculations determined the reactivity of AZM and its protonated forms, identifying the molecular groups involved in the adsorption mechanism.

Evaluation of safety and effectiveness of the LISTENT LCI-20PI cochlear implant in prelingually deafened children

ObjectivesThis prospective multicenter clinical trial was to evaluate the safety and effectiveness of a novel cochlear implant (CI) system, the LISTENT LCI-20PI device in prelingually deafened children (<6 years old). DesignThe LCI-20PI CI system was implanted in 70 prelingually deafened children (<6 years old). The median age (interquartile range) at implantation was 3 years old (2–4 years old). The status of the LCI-20PI devices was evaluated through CI device testing and fitting including measurement of electrically evoked compound action potential (ECAP), electrode impedances, subjective thresholds (T levels), and subjective comfort levels (C levels). The safety and effectiveness of the devices were evaluated during 1-year follow-up. The clinical trial registration number is ChiCTR2200067092. ResultsECAPs were successfully measured in 92.8% (64/70) recipients intraoperatively and in 94.3% (66/70) recipients during device activation. Most of the impedances (99.7%) were within normal limits of 0.7–20 kOhm. The median (interquartile ranges) Meaningful Auditory Integration Scale/Infant-Toddler Meaningful Auditory Integration Scale (MAIS/IT-MAIS) was 95% (85%–97.5%) at 12-month post-activation testing. Median (interquartile range) close-set monosyllabic-word recognition score (MRS) and disyllabic-word recognition score (DRS) in children 3–6 years old at 12-month post-activation testing were 86% (77%–97%) and 90% (70%–100%), respectively. ConclusionsThe new developed LCI-20PI CI device proved safe and effective in prelingually deafened children (<6 years old) in the clinical trial. This CI system could be a cost-effective alternative for prelingually deafened children.

Preparation of silver nanowires with controlled parameters for conductive transparent electrodes

Silver nanowires (AgNWs) have excellent flexibility, unique optical transmittance and high conductivity. The polyol process is appropriate for preparing AgNWs due to its simplicity, effectiveness, low cost, and high yield. This work aims to investigate the effect of preparation parameters of the polyol process on the silver nanowires properties. The parameters include the controlling agent, molecular weight of the polyvinylpyrrolidone (PVP), the temperature, and the reducing agent. The amount of silver nanoparticles formed during preparation was used to determine the optimum preparation conditions. The transmission electron microscope (TEM) images showed minimal amount of Ag nanoparticles when using mixed molecular weight of PVP-40K, and PVP-1.3M at 150 °C with the assistance of copper chloride as a controlling agent. The prepared AgNWs had an average length of 3.7 µm and aspect ratio of 15.3. The fabricated electrodes were characterized using a scanning electron microscope (SEM) and four probe resistivity measurements. The electrical measurement of the AgNWs electrodes indicated that the surfactant thickness is a critical parameter in having low sheet resistance electrodes. Also, the optical transmission was affected by the amount of nanoparticles. The prepared electrode with high concentration of AgNWs and a minimal amount of nanoparticles exhibited 80% optical transmission.

Impact of Binder Content and Type on the Electrochemical Performance of Silicon Anode Materials.

Binders are crucial for stabilizing the cycling performance of silicon (Si) materials by preventing Si particle pulverization during lithiation and delithiation. Poly(acrylic acid) (PAA) and carboxymethyl cellulose (CMC) are the two most studied binders for Si electrodes, with PAA being an elastic polymer and CMC a rigid polymer. Starting with the elastic PAA, in this work the impact of binder content on the cycling performance of Si electrodes is studied. It is found that regardless of Si particle size, there is an optimal binder content between 20 % and 25 % for the cycling stability of Si electrodes. On the other hand, the rigid CMC binder results in lower capacity and faster capacity fading for Si electrodes compared with the elastic PAA. AC-impedance analysis reveals that the lower capacity is due to higher grain boundary resistance (Rgb) in CMC-coated electrodes, leading to high charge-transfer resistance (Rct) and increased polarization. This high polarization triggers premature termination during the discharging process (i. e., the lithiation) of Li/Si cells, underutilizing the Si active material. Additionally, the rapid capacity fading of CMC-coated electrodes is attributed to the rigid binder's inferior ability to prevent Si particle pulverization.

A heterogenous integrated neural recording system with elastocapillary self-assembled Au-PDMS-PEG neural probe and customized ASIC

Abstract This study presents the design and implementation of a heterogenous integrated neural recording system consisting of a flexible Au-PDMS-PEG probe and customized complementary metal oxide semiconductor (CMOS) application-specific integrated circuit (ASIC) in a standard 0.18 μm process. The flexible Au-PDMS-PEG probe was prepared by an elastocapillary self-assembled process, achieving an electrode impedance of 250 kΩ (@1 kHz). The customized CMOS ASIC contains 36 modular digital pixels (MDP). It achieves 5.69 μVrms input referred noise, 10.29 effective number of bits, 49.5 μW power consumption, and 0.092 mm2 area for a single MDP unit. Spontaneous spikes were also recorded in the mouse cortex, with a peak-to-peak amplitude of 389.2 μVPP and a signal-to-noise ratio of 19.36. Benchtop and in-vivo experiments were conducted to validate the functionality and performance of the proposed neural recording system.

An Analytical Model for Electrochemical Tubular Flow Reactors

This paper introduces the first analytical model designed for tubular electrochemical flow reactor, enabling a detailed examination of how reactor geometry and material selection impact performance. The model revealed that certain conditions, such as high electrode resistance relative to charge transfer, electrolyte, and separator resistance, can lead to uneven current distributions and reduced electrode utilization. The model highlights a critical electrode radius, dependent on reactor geometry and material properties, that minimizes the Area Specific Resistance (ASR) while minimizing reactor size. Additionally, it was found that the ASR increases with reactor length, but this effect can be mitigated by using highly conductive electrodes, thus allowing for enhanced power output. These insights provide a foundation for future research and the development of more efficient tubular reactor designs.

Carbon-Binder-Domain porosity extraction through lithium-ion battery electrode impedance data

In the field of 3-D resolved computational modelling of Lithium-ion battery electrodes, the arrangement and properties of the Carbon-Binder-Domain (CBD) play a critical role in the ion and electron transport properties through their impact on the electrode tortuosity factor. However, until now, the CBD porosity value -its main descriptor in terms of transport properties and occupied volume- has been determined through educated guesses due to the lack of an experimental approach. Here, a novel methodology is reported for the determination of the CBD internal porosity through the combination of computational modelling and experimental electrochemical impedance spectroscopy (EIS). The methodology is based on the creation of a calibration curve that relates tortuosity factor with CBD porosity through digital stochastic generation of electrode microstructures and diffusivity characterization. The curve is then compared to the EIS experimental results and analyzed through a transmission line model, yielding a good estimation of the parameters. In this work, the usefulness and the identified limitation of this approach are demonstrated using three different formulations of LiNi0.3Mn0.3Co0.3O2 (NMC 111) cathodes. To the best of the authors’ knowledge, this is the first reported method for estimating CBD porosity.

High Areal Capacitance and Rate Capability of 3D-Printed Thick Electrodes with Optimized Conductive Networks from the Core-Sheath Structure.

Material extrusion 3D printing has received enormous attention to potentially overcome its limits by tailoring and designing thick electrodes. In this work, we prepared a thick reduced graphene oxide/carbon nanotube-reduced graphene oxide/carbon nanotubes/manganese oxide@carbon nanotubes (rGC-rGCMC) electrode with controlled lattice architectures, core-sheath structure, and hierarchical porosity by material coaxial extrusion 3D printing, freeze-drying, and thermal treatment. The volume ratios of core to sheath, including 100%-0%, 0%-100%, 20%-80%, 30%-70%, 40%-60%, and 50%-50%, were designed to investigate the influences of the core-sheath structure on thick electrodes. The electrodes with a core-sheath volume ratio of 30%-70% electrodes exhibited an enhanced areal specific capacitance of 588.27 mF cm-2 (39.48 F g-1) at a scan rate of 0.5 mA cm-2. All capacitance decays from core-sheath electrodes (20%-80%, 30%-70%, 40%-60%, and 50%-50%) were smaller than those from rGCMC (0%-100%) electrodes, indicating the improved rate capability from the core-sheath structure. On comparison of 30%-70% core-sheath electrodes with electrodes made of a homogeneous 30% rGC and 70% rGCMC mixture (30%+70%), lower capacitance (382.27 mF cm-2 and 25.66 F g-1 at 0.5 mA cm-2) of the 30%+70% mixture electrode without a core-sheath structure suggested less efficiency to harvest electrons from the redox reactions. Electrochemical impedance spectroscopy (EIS) data further supported and explained the resistances of thick electrodes with different volume ratios.

Iridium oxide-modified reference screen-printed electrodes for point-of-care portable electrochemical cortisol detection

Cortisol is a well-known stress biomarker; this study focuses on using electrochemical immuno-sensing to measure the concentration of cortisol selectively and sensitively in artificial samples. Anti-cortisol antibodies have been immobilised on polycrystalline Au electrodes via strong covalent thiol bonds, fabricating an electrochemical bio-immunosensor for cortisol detection. IrOx was then anodically electrodeposited as a reference electrode on a commercial screen-printed electrode and electrochemical impedance spectrometry (EIS) studies were used to correlate the electrochemical response to cortisol concentration and the induced changes in charge transfer resistance (Rct). A linear relationship between the Rct and the logarithm of cortisol concentration was found in concentrations ranging from 1 ng/mL to 1 mg/mL with limit of detection at 11.85 pg/mL (32.69 pM). The modification of the reference electrode with iridium oxide has greatly improved the reproducibility of the screen-printed electrode. The sensing system can provide a reliable and sensitive detection approach for cortisol measurements.

The ATLAS RPC Phase-II upgrade for High Luminosity LHC era

Resistive Plate Chambers (RPC) detectors play a crucial role in triggering events containing muons in the central region of ATLAS. In view of the High Luminosity-LHC program, the existing RPC system, consisting of six independent cylindrical detector layers each providing a full space time localization of hits, is currently undergoing a significant upgrade. In the next few years, 306 triplets of new generation RPCs will be installed in the innermost region of the ATLAS Muon Barrel Spectrometer, increasing from 6 to 9 the number of tracking layers, doubling the trigger lever arm. This allows a substantial enhancement of the present trigger redundancy, increasing the coverage from 76% to approximately 96%. Fitting new chambers in the narrow space left in ATLAS inner barrel was a challenge, achieved by optimizing RPC materials and thickness, featuring a 1 mm gas gap (instead of 2 mm), and 1.4 mm resistive electrodes (instead of 1.8 mm) while reaching an high rate capability. To achieve such results, a 100 ps precise Time-to-Digital Converter (TDC) has been integrated in the front-end electronics ASIC. The expected time resolution of a single 1 mm RPC gas gap is approximately 300 ps, and the possibility of a stand-alone Time of Flight measurement will have a huge impact on ATLAS searches for massive long-lived particles. An overview and the present status of the ATLAS RPC Phase-II project will be presented.

A High-Performance, Low Defected, and Binder-Free Graphene-Based Supercapacitor Obtained via Synergistic Electrochemical Exfoliation and Electrophoretic Deposition Process.

An integrated electrochemical exfoliation and electrophoretic deposition (EPD) method is developed to achieve a high-performance graphene supercapacitor. The electrochemical delamination of graphite sheet has obtained a low-defected few-layer graphene adorned with oxygen-containing functional groups. Then, the EPD process produced a binder-free electrode to alleviate the graphene restacking problem. The electrode prepared using a deposition voltage of 5 V exhibits the highest specific capacitance of 145.95 F/g at 0.5 A/g from three-electrode measurement. Moreover, this EPD-prepared electrode also demonstrates superior electrochemical properties compared to electrodes fabricated using PVDF binder. In the real symmetrical cell, the EPD-prepared electrode also shows excellent performance with a high rate capability of 82.31 % (from 0.5 A/g to 10 A/g), high cycling stability of 95.00 % (at 5 A/g) after 10,000 cycles, and rapid frequency response with short relaxation time ( ) of 9.73 ms. These results indicate that this integration method is beneficial to construct a high performance binder-free supercapacitor electrode consisting of low-defected graphene materials, low electrode resistance, and less agglomeration of graphene sheets by utilizing an environmentally friendly process.