Conventional Electrode Configuration Research Articles

Room‐temperature high‐speed mid‐infrared quantum cascade laser with π‐shape metal contact

The authors demonstrate a high-speed 8.5-μm quantum cascade laser (QCL) with room temperature continuous wave (CW) operation. The maximum output power of 141 mW is obtained at 20°C. The parasitic capacitance of the device is decreased from 36.6 to 7.1 pF by monolithic integrating a π-shape metal contact electrode. This results in an increase in the −3 dB RF modulation bandwidth from 870 MHz to 4.5 GHz compared with the conventional electrode configuration.

Hydrothermally Enhanced Tungsten-Tungsten Bronze (W-MxWO3) Electrodes for Pseudocapacitive Energy Storage

Hexagonal tungsten bronzes (h-MxWO3) are an emergent class of pseudocapacitive energy storage material: a metastable phase arranged in a hexagonal crystal structure that enhances the oxide’s rapid intercalation mechanism with impressive capacitances of over 200 F/g and excellent cyclability figures reported. A symmetrical pseudocapacitive device composed of h-MxWO3 electrodes negates the need for expensive and problematic rare minerals such as cobalt and lithium instead using low-cost tungsten whilst offering more efficient high-rate energy storage than commercial lithium-ion batteries.Hexagonal tungsten bronze has shown some promising capacitances in literature in conventional electrode configurations, i.e. composite structures with binder support materials which increase electrode mass impacting specific capacitance. If the bronze was instead grown directly upon a current-collecting substrate, this would negate the need for additional electrode components, with the entire electrode mass participating in storing charge. The present work explores this concept of a novel binder-free electrode design where the nanostructured tungsten-bronze (active material) is grown directly upon a tungsten-based substrate (current collector). This simple design offers potentially higher specific capacitances than conventionally fabricated electrodes.Nanostructured W/h-MxWO3 electrodes were fabricated in a twostep process. Firstly, tungsten foil was oxidised in hot nitric acid, forming a seed layer of monoclinic-WO3. A second step saw the hexagonal bronze deposited upon substrates through a hydrothermal dehydration reaction of sodium tungstate (Na2WO4) where the effect of the directing agent (NaCl, Na2SO4, (NH4)2SO4& Rb2SO4) on the deposited nanostructure was investigated. To assess the benefit of the acid pretreatment step, vis-à-vis a pristine untreated tungsten foil, the hydrothermal reaction was completed upon both a pristine tungsten foil and an acid treated foil. The nanostructured surface deposited from the hydrothermal reaction was characterised by SEM, and the crystal phase identified by XRD. The electrochemical behaviour was analysed using a Biologic SP-300 potentiostat in a 3-electrode cell: as-synthesised foils employed as working electrode; Pt Wire as counter electrode; a saturated calomel electrode (SCE) as reference; and 0.5M H2SO4 as electrolyte. The performance of devices fabricated from two symmetrical as-synthesised electrodes was also characterised using both the potentiostat and a NEWARE battery cycling test system in a two-electrode cell configuration.XRD analysis confirmed that hexagonal-tungsten bronzes were successfully deposited upon substrates irrespective of the substrate pretreatment. The acid pretreatment generally resulted in larger masses of bronze being deposited upon the substrate, but this did not necessarily translate to superior electrochemical performance. The choice of directing agent present in hydrothermal synthesis drastically altered the nature of the deposited layer as may be seen in the provided figure of as-synthesised electrodes (figure b-d). Sodium directed samples formed powder-like deposits (figure b), ammonium sulphate produced larger colloidal bronze layers (figure c) and rubidium sulphate developed glossy smooth sheets (figure d). Additionally, the ratio of tungstate ions (WO4 2-) to directing agent cations (M+) was identified as being critical to obtaining the hexagonal phase. The mechanical stability of the deposited bronze proved problematic, with the layer prone to delamination and disintegration from a variety of mechanisms. A bespoke electrode holder, device testing apparatus and handling procedure was therefore developed to enable repeatable electrode characterization.The cyclic voltammetry response of the hydrothermally deposited layers was typical of an intercalation system, though an initial pseudocapacitive behaviour deteriorated to a battery-like response at sweeprates above 20 mV/s. Galvanostatic charge-discharge testing displayed a significant pseudocapacitive response over limited potential windows; moving beyond these limits produced steep non-linear curves indicating a departure from pseudocapacitive charge transfer processes. The charging at current densities above 1 A/g occurred over rapid time scales showing the electrodes’ suitability for high power applications. Preliminary 3-electrode capacitance results are encouraging with specific capacitances of over 100 Fg-1 by dry mass. The tunnelated M+ ion in the bronze is found to greatly influence the electrochemical performance of the electrode.This work reports the first example of hexagonal tungsten bronze being successfully grown directly on tungsten substrates for application as energy storage electrodes. The binder free electrodes were found to deliver promising performance characteristics in both 3-electrode analysis and in a two-electrode symmetrical device. The performance so far is hampered by the mechanical fragility of the electrode structures, while scale-up of the manufacturing process may prove challenging. The observed mechanism of deposition of hexagonal tungsten bronze from solution to substrate is of interest for future work, as is the significance of tunnelated M+ cations to the hexagonal bronze (h-MxWO3) structure, stability, and electrode performance (figure a). Figure 1

Enhanced Electrodesorption Performance via Cathode Potential Extension during Capacitive Deionization

Complete desorption of contaminants from electrode materials is required for the efficient utilization and long service life of capacitive deionization (CDI) but remains a major challenge. The electrodesorption capacity of CDI in the conventional electrode configuration is limited by the narrow electrochemical stability window of water, which lowers the operating potential to approximately 1.2 V. Here, we report a graphite anode–titanium cathode electrode configuration that extends the cathode potential to −1.7 V and provides an excellent (100%) electrodesorption performance, which is maintained after five cycles. The improvement of the cathode potential depends on the redox property of the electrode. The stronger the oxidizability of the anode and reducibility of the cathode, the wider the cathode potential. The complete desorption potential of SO42− predicted by theoretical electrochemistry was the foundation for optimizing the electrode configuration. The desorption efficiency of Cl− depended on the ionic strength and was negligibly affected by circulating velocities above 112 mL min−1. This work can direct the design optimizations of CDI devices, especially for reactors undergoing chemisorption during the electrosorption process.

Simultaneous orthogonal bipole mapping compared to conventional electrode configurations and impact on ablation strategies: results from a real world observational study

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Background 3D mapping systems are pivotal to identify low voltage areas and to define ablation strategies. In this context, high-density multipolar mapping catheters with varying electrode configurations are used for accurate myocardial substrate definition. High density mapping using a grid shaped catheter allows for use of simultaneous analysis of adjacent orthogonal bipolar signals that may assist in more accurate substrate characterization and ablation strategy decisions. Purpose This was a prospective, multicenter observational study to characterize the utility of electroanatomical mapping with a high density grid-style mapping catheter (HD Grid) in subjects undergoing catheter ablation for persistent atrial fibrillation (PersAF) or ventricular tachycardia (VT) in real-world clinical settings. Methods Mapping was performed with the HD Grid catheter to generate high-density maps of cardiac chambers in order to assess the potential influence of the simultaneous orthogonal bipole configuration on PersAF and VT ablation strategies. Differences in substrate identification between simultaneous orthogonal bipole configuration and standard along-the-spline electrode configuration, and potential effects on ablation strategies were investigated. Results During the study period (January 2019 through April 2020), 367 subjects underwent catheter ablation for PersAF (N = 333, average age 64.1yr, 75% male) or VT (N = 34, average age = 64.3yr, 85.3% male). In total, 494 maps were generated to treat patients undergoing PersAF ablation and 57 to treat patients undergoing VT ablation. Compared to standard along-the-spline configuration, mapping with the simultaneous orthogonal bipole configuration showed differences in 57.8% (178/308) of maps generated, with the greatest difference noticed in surface area of low voltage (62.9%) and location of low voltage (55.6%). In comparisons performed live during the procedure (n = 50), simultaneous orthogonal bipole configuration assisted in identification of ablation targets in 70.0% of cases, changing the ablation strategy compared to that identified with along-the-spline configuration in 34.3%. In comparisons performed retrospectively after the procedure (n = 258), the ablation strategy identified with simultaneous orthogonal bipole configuration differed from along-the-spline configuration in 21.7% of maps. Even compared to a higher-density electrode configuration using all-bipoles rather than along-the-spline bipoles, simultaneous orthogonal bipole configuration identified differences in 57.1% of maps. Conclusion The HD grid catheter combined with simultaneous orthogonal bipole configuration can define myocardial substrate more accurately compared to standard along-the-spline configuration. The difference in substrate identification has potential impact on ablation strategy. Further clinical trials are needed to elucidate the role of orthogonal bipole configuration mapping and improved ablation success rates.

Impact of high density mapping using a grid shaped catheter with orthogonal signal analysis on ventricular tachycardia ablation strategy

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Background Ventricular tachycardia (VT) in patients with structural heart disease (SHD) is related to scar and slow conduction areas. Substrate-based ablation has become the gold standard treatment in patients with SHD-related refractory VT. A new high-density grid shaped catheter that allows simultaneous analysis of adjacent orthogonal bipolar signals can allow better understanding of these slow conduction areas with the potential to improve ablation results. Purpose This was a prospective, multicenter observational study to characterize the utility of electroanatomical mapping with a high density grid-style mapping catheter (HD Grid) in subjects undergoing catheter ablation for ventricular tachycardia (VT) in real-world clinical settings. Methods During the study period, patients who underwent VT ablation using the HD Grid catheter as the primary mapping catheter were included. Comparisons both during the procedure and retrospectively were performed between conventional electrode configuration maps and simultaneous orthogonal bipole electrode configuration maps. The influence of these different configurations on ablation strategy was analyzed. Results During study period (January 2019 – April 2020) 57 maps were performed in 34 VT subjects (average age: 64.3yr, male: 85.3%, ischemic cardiomyopathy: 70.6%). The left ventricle was mapped in 94.1% of subjects, including left ventricular outflow tract and papillary muscles in 20.6% and 8.8% respectively, reporting minimal or no ectopic beats in 97.1% of the subjects. The total number of mapping points collected was 14172.0 ± 15174.8 in 24.3 ± 17.9 min per map. Simultaneous orthogonal bipole mapping identified differences in 67.6% of maps compared to linear along-the-spline electrode configurations. The differences consisted mainly in the surface area (92%) and location of low voltage (40%). When compared during the procedure, simultaneous orthogonal bipole mapping was used to identify ablation strategy in 100% of cases. When compared to a standard along-the-spline configuration retrospectively, the ablation strategy identified with simultaneous orthogonal bipoles was different in 30.1% of cases. The ablation strategy used in these subjects was mainly substrate ablation (late potentials and low voltage areas in scar regions) with an acute success rate of 97.1%. Conclusions The use of the HD Grid catheter with the ability to analyze orthogonal signals is feasible and has the potential to change the ablation strategy in one third of VT patients with a high acute success rate.

Design of Wearable EEG Devices Specialized for Passive Brain-Computer Interface Applications.

Owing to the increased public interest in passive brain–computer interface (pBCI) applications, many wearable devices for capturing electroencephalogram (EEG) signals in daily life have recently been released on the market. However, there exists no well-established criterion to determine the electrode configuration for such devices. Herein, an overall procedure is proposed to determine the optimal electrode configurations of wearable EEG devices that yield the optimal performance for intended pBCI applications. We utilized two EEG datasets recorded in different experiments designed to modulate emotional or attentional states. Emotion-specialized EEG headsets were designed to maximize the accuracy of classification of different emotional states using the emotion-associated EEG dataset, and attention-specialized EEG headsets were designed to maximize the temporal correlation between the EEG index and the behavioral attention index. General purpose electrode configurations were designed to maximize the overall performance in both applications for different numbers of electrodes (2, 4, 6, and 8). The performance was then compared with that of existing wearable EEG devices. Simulations indicated that the proposed electrode configurations allowed for more accurate estimation of the users’ emotional and attentional states than the conventional electrode configurations, suggesting that wearable EEG devices should be designed according to the well-established EEG datasets associated with the target pBCI applications.

Investigation of electro-optical properties for electrochemical luminescence device with a new electrode structure

In this paper, we investigate electrochemical luminescent (ECL) device with a new structure and the ECL cell device with proposed electrode configuration works reliably at AC voltage. In particular, the conventional ECL cell has counter electrodes in which a cathode and an anode are opposed to each other, whereas the proposed structure has parallel electrodes in which a cathode and an anode are arranged on a single substrate. The proposed electrode configuration has a structural feature that electric short-circuiting is less likely to occur during bending than the conventional electrode configuration. The electro-optical characteristics of the new electrode configuration such as the current density, the light emission intensity, and the time evolution of the emission are investigated. The proposed ECL device exhibited higher light emitting efficiency than the conventional structure. Especially, at AC operation mode, the new structure showed the distinctive luminescence characteristic which is combined the first luminescence near the surface of electrode with the delayed second luminescence near the center of between electrodes. It was closely related to the behavior of luminescent particles. The proposed the ECL cell structure is expected to be utilized as a flexible display device by taking advantage of its characteristics and practicality.

Metabolic Assay System Using Skeletal Muscle Cells Cultured with a Stretchable Fiber Electrode

In vitro bioassay systems with cultured living cells have been developed extensively as an alternative to animal experiments to quantify the physiological functions under simplified and controlled conditions. The bioassay systems integrated with an electrical stimulation system have enabled to control electrophysiological activities of the cells such as neural, cardiac, and skeletal muscle cells. Especially, the systems using skeletal muscle cells are one of the promising device to reveal the complex mechanisms of type 2 diabetes and obesity because these diseases are associated with a disorder of insulin- or contraction-induced glucose metabolism in a skeletal muscle cell in vivo. In addition, recent lines of evidence have suggested that the skeletal muscle functions as an endocrine organ that secretes a number of cytokines (myokines) in response to exercise in order to regulate the physiological activities of the whole body including glucose metabolism of the muscle itself. Three-dimensionally reconstructed skeletal muscle cells have been proven to exhibit in vivo-like structural and genetic characteristics, and therefore, various three dimensional culture technique has been developed. On the other hand, extracellular electrical stimulation using a pair of electrodes immersed in both sides of a culture medium still has technical problems concerning limitations on the current value, which can be applied without a faradic reaction causing perturbation of culture conditions such as pH value. Additionally, in the conventional electrode configuration, most of the applied current tends to pass only through the culture medium surrounding the insulative living cells, which cannot cause cell depolarization effectively. For reliable and reproducible bioassay, it is necessary to develop the low invasive electrical stimulation culture system in which the applied current can pass through the cells. In this study, we developed the in vitro bioassay systems with three dimensional skeletal muscle fiber enclosing a stretchable and biocompatible electrode wire composed of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and polyurethane (PU). The fibrous PEDOT has much capacity in its electrical double layer even in a composite form with PU that can apply current charge required for excitation of the surrounding skeletal muscle cells without any faradaic reaction. The electric current can pass through the cells surrounding the electrode wire, resulting in their quantitative depolarization, which was demonstrated by visualizing intracellular Ca2+ transients upon applied electrical stimulation with a Ca2+-sensitive fluorescent dye. PEDOT/PU wire was fabricated by twisting the PEDOT/PU strip (30 mm x 3 mm, 3 μm in thickness) cut out from the film. The PEDOT/PU film was prepared by spin-coating a precursor solution of EDOT monomer, pTSFe(III) dopant, and PU, followed by thermal polymerization of PEDOT on a glass substrate. Cyclic voltammetry measured in 0.1 M KCl solution suggested that maximum charge storing in an electric double layer of the PEDOT/PU wire was 75 μC. The wire was centrally set into the PDMS chamber pretreated with cell repulsive polymer solution. The C2C12 myoblast cells suspended in the mixture of collagen and Matrigel were poured into the PDMS chamber and incubated for 30min at 37 oC to facilitate gelation of the mixture. During three days of culture, the seeded cells self-assembled around the PEDOT/PU wire contracting the collagen/Matrigel matrix, resulting in a fiber form of myoblast cells/collagen/Matrigel matrix fiber around the PEDOT/PU wire. The cells were continuously cultured in the medium for additional seven days to induce differentiation of the myoblasts into the myotubes. Fluorescent Live/Dead imaging showed that almost all the myotubes around the PEDOT/PU electrode wire in alive suggesting non-citotoxity of the PEDOT/PU wire itself. The myotubes were aligned to longitudinal direction of the wire, which is similar structure as in vivo skeletal muscle tissue. Upon application of the constant current pulses to the PEDOT/PU electrode wire against a carbon electrode set outside of the myotubes/collagen/Matrigel matrix fiber, the cells exhibited twitch and tetanus contraction depending on the applied electric pulse frequency. The threshold current charge evaluated by visualizing intracellular Ca2+ transients upon applied electrical stimulation was 1.0 μC which value was much smaller than maximum charge derived from the electric double layer of PEDOT/PU wire, 75 μC. This suggested low invasive electric stimulation of the PEDOT/PU electrode even in close to the surrounding cells. Additional utility of embedding the electrode into the three dimensional skeletal muscle fiber was successfully demonstrated by selective electrical stimulation of the skeletal muscle fiber arrays in the same culture medium, that is beneficial for high-contrast comparison of the contraction effect on the skeletal muscle cellular functions such as contraction-dependent myokine secretion activity and contraction-dependent control of glucose metabolism in type 2 diabetes.

The use of the multiple-gradient array for geoelectrical resistivity and induced polarization imaging

The use of most conventional electrode configurations in electrical resistivity survey is often time consuming and labour intensive, especially when using manual data acquisition systems. Often, data acquisition teams tend to reduce data density so as to speed up field operation thereby reducing the survey cost; but this could significantly degrade the quality and resolution of the inverse models. In the present work, the potential of using the multiple-gradient array, a non-conventional electrode configuration, for practical cost effective and rapid subsurface resistivity and induced polarization mapping was evaluated. The array was used to conduct 2D resistivity and time-domain induced polarization imaging along two traverses in a study site at Ota, southwestern Nigeria. The subsurface was characterised and the main aquifer delineated using the inverse resistivity and chargeability images obtained. The performance of the multiple-gradient array was evaluated by correlating the 2D resistivity and chargeability images with those of the conventional Wenner array as well as the result of some soundings conducted along the same traverses using Schlumberger array. The multiple-gradient array has been found to have the advantage of measurement logistics and improved image resolution over the Wenner array.

Onsager Principle and Electrorheological Fluid Dynamics

We present the formulation of a two-phase, electrical-hydrodynamic model for the description of electrorheological fluid dynamics, based on the Onsager principle of minimum energy dissipation. By considering the energetics of (induced) dipole-dipole interaction between the solid particles in terms of a field variable n(� x ), we employ the Onsager principle to derive the relevant coupled hydrodynamic equations, together with a continuity equation for n(� x ). Numerical solution of the relevant equations yields predictions that display very realistic behaviors as seen experimentally. In particular, we show that while the predicted results have features that resemble Bingham fluids, there can be important differences. For example, the yield stress obtained by extrapolating the shear rate to zero is 30-40% lower than that obtained from the maximum of the stress-strain relation. Moreover, for the conventional electrode configuration where the field is perpendicular to the shearing direction, there is very clear shearing-thinning effect that has been seen experimentally.

Trepanning of Al 2O 3 by electro-chemical discharge machining (ECDM) process using abrasive electrode with pulsed DC supply

Electro-chemical discharge machining (ECDM) of electrically non-conductive high-strength–high-temperature-resistant ceramics such as aluminium oxide (Al 2O 3) by trepanning method (i.e. orbital motion of tool) has shown the possibility of drilling large size holes by comparatively smaller electrodes efficiently and economically. However, at greater machined depth, the conventional electrode configurations and machining parameters show that machining performance gradually deteriorates with increase in tool depth and finally cause micro cracks on the machined surface due to thermal shocks at high voltage. To reduce this problem and to enhance the machining performance during trepanning operation of Al 2O 3, a spring fed cylindrical abrasive electrode of 1.5 mm diameter has been used under the effect of the three most influential parameters, namely, pulsed DC supply voltage, duty factor and electrolyte conductivity, each at five different levels to assess the volume of material removed, machined depth and diameteral overcut. The results obtained from this study revealed that pulsed DC has reduced the tendency of cracking at high supply voltage compared to smooth DC and the machining ability of the abrasive electrode was better than copper electrode as it would enhance the cutting ability due to the presence of abrasive grains during machining. In addition to this, trepanning provides the scope for drilling bigger holes.

Independent Component Analysis of High-Density Electromyography in Muscle Force Estimation

Accurate force prediction from surface electromyography (EMG) forms an important methodological challenge in biomechanics and kinesiology. In a previous study (Staudenmann et al., 2006), we illustrated force estimates based on analyses lent from multivariate statistics. In particular, we showed the advantages of principal component analysis (PCA) on monopolar high-density EMG (HD-EMG) over conventional electrode configurations. In the present study, we further improve force estimates by exploiting the correlation structure of the HD-EMG via independent component analysis (ICA). HD-EMG from the triceps brachii muscle and the extension force of the elbow were measured in 11 subjects. The root mean square difference (RMSD) and correlation coefficients between predicted and measured force were determined. Relative to using the monopolar EMG data, PCA yielded a 40% reduction in RMSD. ICA yielded a significant further reduction of up to 13% RMSD. Since ICA improved the PCA-based estimates, the independent structure of EMG signals appears to contain relevant additional information for the prediction of muscle force from surface HD-EMG.

High‐Performance Bottom‐Contact Organic Thin‐Film Transistors with Controlled Molecule‐Crystal/Electrode Interface

An improvement of the performance of bottom-contact organic thin-film transistors is demonstrated by embedding and planarizing the source/drain electrodes in a gate dielectric. The electric contact with the pentacene active layer is superior to conventional electrode configurations because of the favorable growth of pentacene grains adjacent to the source/drain electrode edges: these can be seen in the figure.

Electrochemical and In Situ Optical Characterization of Single Micrometer-Size Particles of Spherical Nickel Oxide in Alkaline Aqueous Electrolytes

A method is herein described for the micromanipulation and subsequent in situ, real-time optical and spectroscopic characterization of individual micrometer-size particles of electrochemically active materials under potential control. This novel approach relies on the use of a micropipette to capture, by suction, single particles, which are then attached to the surface of a glass-encased microelectrode placed inside an empty, shallow Petri dish, and held in position by a small glass rod in the form of truncated cone. This configuration allows for particles to be placed directly beneath the microscope objective enabling visual and spectroscopic monitoring during electrochemical measurements by simply filling the dish with sufficient electrolyte to completely cover the particle and make electrolytic contact with a reference and a counter electrode. Illustrations are provided for particles of spherical Ni hydroxide, S-Ni(OH) 2 , in alkaline solutions, which following activation at fairly positive potentials, yielded an electrochemical response characteristic of Ni(OH) 2 in more conventional electrode configurations. The much darker appearance of NiOOH compared to the virtually translucent character of virgin S-Ni(OH) 2 allowed for the spatial and temporal evolution of charge flow within the microparticle to be monitored in real time during the first scan in the positive direction using computer-controlled video imaging.

Electrical resistivity measurements of polymer materials

Basic methods of measuring volume and surface resistivities are reviewed in relation to the wide range of values encountered in plastics and rubbers, including antistatic grades, conducting composites and intrinsically conductive polymers. The application of conventional electrode configurations of 2, 3 and 4 terminal types is considered first. Then the performance and reliability of various probe techniques are analysed. Finally, the observation of charge decay rates is discussed as a means of determining resistivities, and its limitations are defined.

Radiation Damage Resistance of Reverse Electrode GE Coaxial Detectors

Two high-purity germanium coaxial detectors, having opposite electrode configurations from one another, but fabricated from the same germanium crystal, were irradiated simultaneously with fast neutrons from an unmoderated 252Cf source. Both detectors were 42 mm diam. The detector having the conventional electrode configuration was about 28 times more sensitive to radiation damage than was the detector having the p+ contact on the coaxial periphery. These results prove that germanium coaxial detectors having the conventional electrode configuration should not be used in any situation subject to significant radiation damage. This conclusion was anticipated because the defects produced by neutron and proton irradiation of germanium act predominantly as hole traps.