Electrode Alignment Research Articles

Electrolyte Reactivity on Graphite and Copper as Measured in Lithium Double Half Cells

The study of electrolyte reactivity on electrode materials is fundamental to understand the service life of lithium ion batteries (LIBs). In this paper, a new type of symmetric cells, termed double half-cells (DHC), has been designed to evaluate electrolyte reactivity precisely and accurately while only using a standard charger. The construction of DHCs avoids the disassembly/assembly process and electrode alignment issues associated with conventional symmetric cells, resulting in improved performance and reliability. Using DHCs, electrolyte reactivity on graphite and copper were investigated. While electrolyte reactivity on Cu and graphite were found to be low at room temperature, elevated temperatures resulted in significant electrolyte reactivity on both surfaces. The addition of vinylene carbonate to the electrolyte was found to have little effect on graphite electrodes, but results in severe electrolyte decomposition on copper. These results show the utility of DHCs and also that inactive materials, such as current collectors, should not be ignored when considering electrolyte decomposition reactions in Li-ion cells.

Impedance Evolution Characteristics in Lithium-Ion Batteries

A three-electrode cell can be a useful tool for measuring electrode-level and cell-level electrochemical characteristics, such as the impedance response and potential variations in lithium-ion cells. In this paper, a reliable three-electrode coin cell setup is introduced, which improves the stability and accuracy of electrochemical measurements by modifying the electrode alignment and employing Li4Ti5O12 as a reference electrode. An important highlight is the ability to obtain impedance evolution characteristics at different depth of discharge (DOD) for an individual electrode and the full cell based on both the frequency response analysis and the carrier function Laplace transform characteristics. The reliability of the proposed modified three-electrode coin cell setup has been validated by analyzing the impedance response of symmetric and full cells, and the voltage profiles of the full cell along with the positive/negative electrode contributions. The importance of the resistance contributions from the negative and positive electrodes to the full cell impedance evolution at different DOD is highlighted.

Capacitive tactile sensor with asymmetric electrodes for angle-detection-error alleviation

A capacitive tactile sensing unit with an asymmetric electrode arrangement to support tolerable angle detection errors (ADEs) in processes and operations was proposed and demonstrated in this study. Each capacitor in the sensing unit contains one fan-shaped electrode on top and one square-shaped electrode at the bottom with an intentional shift on the xy-plane, which alleviated the rotational misalignment and suppressed shear force ADE from more than 2.5° to less than 0.4°. The suppression of the ADE was realized by enlarging the sector angle of the fan-shaped electrode to 100°, which provided 5° clockwise and 5° counterclockwise coverages for electrode alignment. Complete theoretical derivation of the relationships among the capacitors, design, simulation, and measurement was conducted in this research. Experimental results proved that this fan-shaped electrode design showed identical functionalities and sensitivities to those of the square-shaped electrode design for capacitive tactile sensing applications.

The new ECR charge breeder for the Selective Production of Exotic Species project at INFN—Laboratori Nazionali di Legnaro

The Selective Production of Exotic Species (SPES) project is an ISOL facility under construction at Istituto Nazionale di Fisica Nucleare-Laboratori Nationali di Legnaro (INFN-LNL). 1+ radioactive ions, produced and extracted from the target-ion-source system, will be charge bred to high charge states by an ECR charge breeder (SPES-CB): the project will adopt an upgraded version of the PHOENIX charge breeder, developed since about twenty years by the Laboratoire de Physique Subatomique et de Cosmologie (LPSC). The collaboration between LNL and LPSC started in 2010 with charge breeding experiments performed on the LPSC test bench and led, in June 2014, to the signature of a Research Collaboration Agreement for the delivery of a complete charge breeder and ancillaries, satisfying the SPES requirements. Important technological aspects were tackled during the construction phase, as, for example, beam purity issues, electrodes alignment, and vacuum sealing. This phase was completed in spring 2015, after which the qualification tests were carried out at LPSC on the 1+/q+ test stand. This paper describes the characteristics of the SPES-CB, with particular emphasis on the results obtained during the qualification tests: charge breeding of Ar, Xe, Rb, and Cs satisfied the SPES requirements for different intensities of the injected 1+ beam, showing very good performances, some of which are "best ever" for this device.

Characterization of electrode alignment for optimal droplet charging and actuation in droplet-based microfluidic system.

The actuation method using electric force as a driving force is utilized widely in droplet-based microfluidic systems. In this work, the effects of charging electrode alignment on direct charging of a droplet on electrified electrodes and a subsequent electrophoretic control of the droplet are investigated. The charging characteristics of a droplet according to different electrode alignments are quantitatively examined through experiments and systematic numerical simulations with varying distances and angles between the two electrodes. The droplet charge acquired from the electrified electrode is directly proportional to the distance and barely affected by the angle between the two electrodes. This implies that the primary consideration of electrode alignment in microfluidic devices is the distance between electrodes and the insignificant effect of angle provides a great degree of freedom in designing such devices. Not only the droplet charge acquired from the electrode but also the force exerted on the droplet is analyzed. Finally, the implications and design guidance for microfluidic systems are discussed with an electrophoresis of a charged droplet method-based digital microfluidic device.

Interference Reduction in Glucose Detection by Redox Potential Tuning: New Glucose Meter Development.

A new glucose meter was developed employing a novel disposable glucose sensor strip comprising a nicotinamide adenine dinucleotide-glucose dehydrogenase (NAD-GDH) and a mixture of Fe compounds as a mediator. An iron complex, 5-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)-1,10-phenanthroline iron(III) chloride (Fe-PhenTPy), was synthesized as a new mediator for the NAD-GDH system. Due to the high oxidation potential of the mediator, the detection potential was tuned to be more closely fitted toward the enzyme reaction potential, less than 400 mV (vs. Ag/AgCl), by mixing with an additional iron mediator. The impedance spectrometry for the enzyme sensor containing the mixed mediators showed an enhanced charge transfer property. In addition, a new cartridge-type glucose meter was manufactured using effective aligned-electrodes, which showed an enhanced response compared with conventional electrode alignment. The proposed glucose sensor resulted in a wide dynamic range in the concentration range of 30 - 500 mg dL(-1) with a reduced interference effect and a good sensitivity of 0.57 μA mM(-1).

Exploring the electrodes alignment and mushrooming effects on weld geometry of dissimilar steels during the spot welding process

The class two of RWMA electrode caps has very common application-purpose for the welding of steels and withstand for high thermal application on wrought cast. It has been experimentally used to weld carbon and stainless steels up to 900 weld attempts using AC waveform, C-type JPC 75 kVA, Japanese made spot welder. So the electrode alignments and resulting mushrooming effects are finally analysed in this research as well as the weld geometry of dissimilar (carbon and stainless) steels. When considering such weld joints, the heat imbalances are very interesting factors on spot welding research and therefore I have simulated the dissimilar weld joints using Ansys 14. Initially, it was simulated and later those results are compared with real welded samples. The common welded regions such as: fusion zones, heat affected zones, heat extended zones and base metals are all well-noticed for carbon steel sides but not for stainless steel sides. Besides, the electrode mushrooming effect on both sides of electrodes are not parallel deterioration and it has some demerits on internal structure indeed. Some of the dissimilar welded samples and electrode caps are eventually underwent metallurgical test to identify the improper alignment.

Application of phase coherence in assessment of spatial alignment of electrodes during simultaneous endocardial-epicardial direct contact mapping of atrial fibrillation.

Mapping and interpretation of wave conduction patterns recorded during simultaneous mapping of the electrical activity on both endocardial and epicardial surfaces are challenging because of the difficulty of reconstruction of reciprocal alignment of electrodes in space. Here, we suggest a method to overcome this difficulty using a concept of maximized endo-epicardial phase coherence. Endo-epicardial mapping was performed in six humans during induced atrial fibrillation (AF) in right atria using two sets of 8 × 8 electrode plaques. For each electrode, mean phase coherence (MPC) with all electrodes on the opposite side of the atrial wall was calculated. Localization error was defined as a distance between the directly opposing electrode and the electrode with the maximal MPC. Overall, there was a linear correlation between MPC and distance between electrodes with R(2) = 0.34. Localization error obtained for electrodes of the plaque in six patients resulted in a mean 2.3 ± 1.9 mm for 25 s electrogram segment length. Eighty-four per cent of the measurements resulted in error smaller than 3.4 mm. The duration of the recording used to compute MPC was negatively correlated with localization error; however, the effect reached plateau for segment durations longer than 15 s. Application of the concept of maximized endo-epicardial phase coherence to electrograms during AF allows reconstruction of reciprocal alignment of the electrodes on the opposite side of the atrial wall. This approach may be especially useful in settings where the spatial position of endo- and epicardial electrodes for intracardiac mapping cannot otherwise be determined.

Improving the field-effect performance of Bi2S3 single nanowires by an asymmetric device fabrication.

High-quality Bi2 S3 nanowires are synthesized by chemical vapor deposition and their intrinsic photoresponsive and field-effect characteristics are explored in detail. Among the studied Au-Au, Ag-Ag, and Au-Ag electrode pairs, the device with stepwise band alignment of asymmetric Au-Ag electrodes has the highest mobility. Furthermore, it is shown that light can cause a sevenfold decrease of the on/off ratio. This can be explained by the photoexcited charge carriers that are more beneficial to the increase of Ioff than Ion . The photoresponsive properties of the asymmetric Au-Ag electrode devices were also explored, and the results show a photoconductive gain of seven with a rise time of 2.9 s and a decay time of 1.6 s.

Metal oxide induced charge transfer doping and band alignment of graphene electrodes for efficient organic light emitting diodes.

The interface structure of graphene with thermally evaporated metal oxide layers, in particular molybdenum trioxide (MoO3), is studied combining photoemission spectroscopy, sheet resistance measurements and organic light emitting diode (OLED) characterization. Thin (<5 nm) MoO3 layers give rise to an 1.9 eV large interface dipole and a downwards bending of the MoO3 conduction band towards the Fermi level of graphene, leading to a near ideal alignment of the transport levels. The surface charge transfer manifests itself also as strong and stable p-type doping of the graphene layers, with the Fermi level downshifted by 0.25 eV and sheet resistance values consistently below 50 Ω/sq for few-layer graphene films. The combination of stable doping and highly efficient charge extraction/injection allows the demonstration of simplified graphene-based OLED device stacks with efficiencies exceeding those of standard ITO reference devices.

Encapsulate-and-peel: fabricating carbon nanotube CMOS integrated circuits in a flexible ultra-thin plastic film

Fabrication of single-walled carbon nanotube thin film (SWNT-TF) based integrated circuits (ICs) on soft substrates has been challenging due to several processing-related obstacles, such as printed/transferred SWNT-TF pattern and electrode alignment, electrical pad/channel material/dielectric layer flatness, adherence of the circuits onto the soft substrates etc. Here, we report a new approach that circumvents these challenges by encapsulating pre-formed SWNT-TF-ICs on hard substrates into polyimide (PI) and peeling them off to form flexible ICs on a large scale. The flexible SWNT-TF-ICs show promising performance comparable to those circuits formed on hard substrates. The flexible p- and n-type SWNT-TF transistors have an average mobility of around 60 cm2 V−1 s−1, a subthreshold slope as low as 150 mV dec−1, operating gate voltages less than 2 V, on/off ratios larger than 104 and a switching speed of several kilohertz. The post-transfer technique described here is not only a simple and cost-effective pathway to realize scalable flexible ICs, but also a feasible method to fabricate flexible displays, sensors and solar cells etc.

Contact System Design to Improve Energy Efficiency in Copper Electrowinning Processes

To improve energy efficiency in copper electrowinning, different technologies have been developed. These include electrode positioning capping boards and 3-D grids, electrode spacers, and segmented intercell bars. This paper introduces a design concept to avoid electrode open circuits and reduce contact resistances. The design is based on a female tooth shape for the contacts on the intercell bar. This leads to improved electrode alignment, reduced contact resistances, easier contact cleaning, and ensured electrical contact for the electrodes. It results in lower operational temperature for the electrodes, reduced plant housekeeping, increased lifespan for capping boards, and higher rate of grade A copper production. The comparative results presented should be a useful guideline for any type of intercell bar. Improvements in production levels and energy efficiency should reach 0.5% and 3%, respectively. A 3-D finite-element-based analysis and industrial measurements are used to verify the results.

Microfluidic Chip-Based Online Electrochemical Detecting System for Continuous and Simultaneous Monitoring of Ascorbate and Mg2+ in Rat Brain

This study demonstrates a microfluidic chip-based online electrochemical detecting system for in vivo continuous and simultaneous monitoring of ascorbate and Mg(2+) in rat brain. In this system, a microfluidic chip is used as the detector for both species. To fabricate the detector, a single-channel microfluidic chip is developed into an electrochemical flow cell by incorporating the chip with an indium-tin oxide (ITO) electrode as working electrode, an Ag/AgCl wire as reference electrode, and a stainless steel tube as counter electrode. Selective detection of ascorbate and Mg(2+) is achieved by drop-coating single-walled carbon nanotubes (SWNTs) and polymerizing toluidine blue O (polyTBO) film onto the ITO electrode, respectively. Moreover, the alignment of SWNT-modified and polyTBO-modified electrodes and the solution introduction pattern are carefully designed to avoid any cross talk between two electrodes. With the microfluidic chip-based electrochemical flow cell as the detector, an online electrochemical detecting system is successfully established by directly integrating the microfluidic chip-based electrochemical flow cell with in vivo microdialysis. The microfluidic system exhibits sensing properties with a linear relationship from 5 to 100 μM for ascorbate and from 100 to 2000 μM for Mg(2+). Moreover, this system demonstrates a high selectivity and stability and good reproducibility for simultaneous measurements of ascorbate and Mg(2+) in a continuous-flow system. These excellent properties substantially render this system great potential for continuous and simultaneous online monitoring of ascorbate and Mg(2+) in rat brain.

Electrode localization for planning surgical resection of the epileptogenic zone in pediatric epilepsy

In planning for a potentially curative resection of the epileptogenic zone in patients with pediatric epilepsy, invasive monitoring with intracranial EEG is often used to localize the seizure onset zone and eloquent cortex. A precise understanding of the location of subdural strip and grid electrodes on the brain surface, and of depth electrodes in the brain in relationship to eloquent areas is expected to facilitate pre-surgical planning. We developed a novel algorithm for the alignment of intracranial electrodes, extracted from post-operative CT, with pre-operative MRI. Our goal was to develop a method of achieving highly accurate localization of subdural and depth electrodes, in order to facilitate surgical planning. Specifically, we created a patient-specific 3D geometric model of the cortical surface from automatic segmentation of a pre-operative MRI, automatically segmented electrodes from post-operative CT, and projected each set of electrodes onto the brain surface after alignment of the CT to the MRI. Also, we produced critical visualization of anatomical landmarks, e.g., vasculature, gyri, sulci, lesions, or eloquent cortical areas, which enables the epilepsy surgery team to accurately estimate the distance between the electrodes and the anatomical landmarks, which might help for better assessment of risks and benefits of surgical resection. Electrode localization accuracy was measured using knowledge of the position of placement from 2D intra-operative photographs in ten consecutive subjects who underwent intracranial EEG for pediatric epilepsy. Average spatial accuracy of localization was 1.31 ± 0.69 mm for all 385 visible electrodes in the photos. In comparison with previously reported approaches, our algorithm is able to achieve more accurate alignment of strip and grid electrodes with minimal user input. Unlike manual alignment procedures, our algorithm achieves excellent alignment without time-consuming and difficult judgements from an operator.

Experimental and theoretical investigations of some useful langasite cuts for high-temperature SAW applications

Passive high-temperature sensors are a most promising area of use for SAW devices. Langasite (La3Ga5SiO14; LGS) has been identified as promising piezoelectric material to meet high-temperature SAW challenges. Because it is necessary to know the material behavior for an accurate device design, the frequency¿temperature behavior of Rayleigh SAW (R-SAW) and shear-horizontal SAW (SH-SAW) LGS cuts is investigated on delay line and resonator test structures up to 700°C by RF characterization. In the range of the 434-MHz ISM band, the (0°, 22°, 90°) SH-SAW cut shows thermal behavior similar to the (0°, 138.5°, 26.7°) R-SAW cut. Associated with the (0°, 22°, 31°) cut, in which SAWs present mixed types of polarization, the (0°, 22°, 90°) SH-SAW orientation might allow differential measurements on a single substrate. In the temperature range of 400 to 500°C, delay line test devices using the SH-SAW cut show a considerable drop of signal. Theoretical analysis indicates that this newly described behavior might be a result of anisotropy effects in this cut, occurring in case of any slight misorientation of electrode alignment.

Thoracic wall pain from spinal cord stimulator electrode malfunction

Spinal cord stimulators (SCSs) produce electrical signals to suppress perception of chronic neuropathic pain, but they can have complications. We present a case of thoracic wall dysesthesia associated with spinal cord stimulator use due to leakage current from electrode degeneration. Case: A 51 y/o female presented with new left sided chest pain with usage of her SCS. Patient had history of multiple back surgeries and failed back surgery syndrome. Ten year previously, she had a SCS implanted with 2 Medtronic Pisce percutaneous-style 4 contact electrodes at the T8-T9 spinal levels for low back and left leg pain. She had excellent pain relief until 14 months after initial implantation, when the SCS was revised due to increasing voltage demands. Electrodes were replaced with a Specify 4x2 paddle electrode at T8-T9. After 7 years she abruptly started to experience left sided chest wall pain consistently during SCS activation despite multiple attempts at reprogramming. Imaging displayed perfect midline and dorsal electrode alignment with no migration from previous studies. There were, however, signs of discontinuity in some contacts. After multidisciplinary discussions between pain medicine, neurosurgery, neuroradiology, we hypothesized that leakage current could be causing the thoracic dysesthesias, and the patient was offered another revision with a new paddle electrode. During surgery the left electrode appeared to have a defect in the insulation. A Specify 8x2 paddle electrode was then placed. Excellent relief of the patient’s neuropathic pain was achieved, with complete resolution of the thoracic dysesthesias during stimulation. New SCS related dysesthesia in a previously well-functioning system is not commonly reported in the absence of lead migration. This case demonstrates the possibility of aberrant electrical current paths that can develop over time, particularly as electrodes age and fray. Electrode revision should be considered, particularly if impedance values in the existing electrode are abnormal.

Numerical analysis of arc plasma and weld pool formation by a tandem TIG arc

Multi-electrode welding processes are used in various industrial fields for higher productivity. These processes can use many combinations of welding methods, current values and polarities, and electrode alignments. However, this complicates welding phenomena. In this research, we focused on the tandem tungsten inert gas (TIG) arc, which is a relatively simple multi-electrode welding process. We performed a numerical investigation into the tandem TIG arc plasma and weld pool formation to clarify the phenomena involved. The weld spot of a tandem TIG weld is ellipsoidal in appearance and is deeper than that of a single-electrode TIG weld. Reduction in the shear stress of the plasma flow in the tandem TIG weld leads to a deeper penetration. Furthermore, the influence of the electrode alignment is calculated, and it is determined that the weld spot appearance significantly changes. The appearance is strongly related to the arc plasma shape. These numerical results show good agreement with the experimental results, which proves that our model has relatively high reliability.

Note: Detecting flow velocity with high purity semiconducting single-walled carbon nanotubes

We report the measurement of fluid velocity on a semiconducting single-walled carbon nanotubes film in a microfluidic channel. To investigate the mechanism related to electrical signal change, we performed various experiments along with changing the flow velocity, the ion concentration and liquid viscosity, etc. Our result suggests that the sensing of flow velocity is a closely related to a pulsating asymmetrical thermal ratchet model. The electric signal change was strongly dependent on the electrode alignment, and the channel width of the sample. As the result, we achieved highly sensitive detection of the fluid, roughly 4 times greater than previous results.

Flow-induced voltage generation in non-ionic liquids over monolayer graphene

To clarify the origin of the flow-induced voltage generation in graphene, we prepared a new experimental device whose electrodes were aligned perpendicular to the flow with a non-ionic liquid. We found that significant voltage in our device was generated with increasing flow velocity, thereby confirming that voltage was due to an intrinsic interaction between graphene and the flowing liquid. To understand the mechanism of the observed flow-induced voltage generation, we systematically varied several important experimental parameters: flow velocity, electrode alignment, liquid polarity, and liquid viscosity. Based on these measurements, we suggest that polarity of the fluid is a significant factor in determining the extent of the voltage generated, and the major mechanism can be attributed to instantaneous potential differences induced in the graphene due to an interaction with polar liquids and to the momentum transferred from the flowing liquid to the graphene.

Electro-optical control in a plasmonic metamaterial hybridised with a liquid-crystal cell

We experimentally demonstrate efficient electro-optical control in an active nano-structured plasmonic metamaterial hybridised with a liquid-crystal cell. The hybridisation was achieved by simultaneously replacing the polarizer, transparent electrode and molecular alignment layer of the liquid-crystal cell with the metamaterial nano-structure. With the control signal of only 7 V we have achieved a fivefold hysteresis-free modulation of metamaterial transmission at the wavelength of 1.55 µm.