Segmented Electrodes Research Articles

Corrosion electrochemistry with a segmented array bipolar electrode

Bipolar electrochemistry was applied to determine the full spectrum of anodic-to-cathodic polarisation behaviour of stainless steel. The potential and current distributions at the sample surface were determined using a segmented array bipolar electrode (BPE). The measured potential shows a quasi-linear gradient along the centre of the BPE, with the current following an exponential Butler–Volmer-type relationship. Bipolar electrochemistry is compared to conventional 3-electrode polarisation testing, allowing determination of the critical pitting potential, general corrosion rates and the cathodic current response. The application of bipolar electrochemistry is demonstrated via measurement of pit growth kinetics in ferritic stainless steel.

Dielectric barrier micro-plasma reactor with segmented outer electrode for decomposition of pure CO2

Four coaxial cylinder dielectric barrier discharge micro-plasma reactors were designed for the non-catalytic decomposition of pure CO2 into CO and O2 at low temperature and ambient pressure. The influence of segmented outer electrodes on the electrical characteristics and the reaction performance was investigated. Experimental results indicated that the introduction of segmented outer electrodes can significantly promote the decomposition of CO2. Encouragingly, the highest conversion of 13.1% was obtained at an applied voltage of 18 kV, which was a substantial increase of 39.4% compared to the traditional device. Compared with other types of dielectric barrier discharge plasma reactors, the proposed segmented outer electrode micro-plasma reactor can give a higher CO2 conversion and acceptable energy efficiency. The increase in conversion can be attributed mainly to the enhanced corona discharge caused by the fringe effect at electrode edges, the increase in energy density and the increase in the number of micro-discharges. In addition, detailed electrical characterization was performed to reveal some trends in the electrical behavior of proposed reactors.

Facile segmented graphite felt electrode for iron-vanadium redox flow batteries with deep eutectic solvent (DES) electrolyte

In this work, the graphite felt electrode for an iron-vanadium redox flow battery (RFB) with deep eutectic solvent (DES) electrolyte is modified by the method of electrolysis in ammonium sulfate, and a segmented electrode is prepared by combining the pristine graphite felt part and the modified part. The electrolysis process not only makes the outermost layer of graphite felt partially fall off which enlarges the specific surface area, but also increases the number of oxygen-containing functional groups on the surface of the graphite felt. To uniform the electrochemical reaction along the electrolyte flow direction and reduce the over-potential, the pristine graphite felt part of the segmented electrode is placed in the electrolyte inlet region, and the modified graphite felt part is put in the outlet region. With the segmented electrode, the single cell test shows the maximum power density is 10.63% higher than that of the pristine electrode under the same operating condition, and the energy efficiency is also higher for charge-discharge cycles. Therefore, the accessibly prepared segmented electrode is promising for improving the performance of the DES electrolyte redox flow battery.

Method for production of aligned nanofibers and fiber elasticity measurement

A novel method for collection of electrospun polymer nanofibers is proposed. This method can be applied to extrusion of various polymers and deposition on various types of substrates or without use of a substrate at all. The fiber is forced to alternate in its deposit in between two different segments of a collector electrode by a pair of square electric potential functions in anti-phase applied to these two electrode segments. As the fiber oscillation frequency is equal to the potential function frequency, the fiber deposition rate in between these two collector segments can be controlled. If an electrically non-conductive material is placed in between the two segments of the collector electrode, aligned fibers are simply deposited on the surface of this material. The method is used to perform stiffness measurements of the fibers demonstrating Young's modulus of 200.1 MPa with a standard deviation of 30.7 MPa. The stiffness measurement does not require any specialized equipment and requires minimal sample preparation. A sample consists of known amount of aligned fibers collected between a pair of thin coaxial rods leading to a cylindrical bundle with known number of fibers. A tensile test is then performed to obtain stress-strain curve and to find the Young's modulus of the fiber material.

Elastic Wave Properties of an Adaptive Electromechanical Metamaterial Beam

An adaptive metamaterial beam with a couple of electromechanical resonators in each unit cell is proposed in this study to open Bragg bandgap or locally resonant bandgap for flexural wave attenuation in Euler–Bernoulli beams. The electromechanical resonator is composed of a piezoelectric layer with segmented electrodes and shunt circuits, which affect the dynamic equivalent stiffness. It is illustrated that there is only a Bragg bandgap when the circuits of the two adjacent resonators are approximate to a short circuit or open circuit, and the locally resonant bandgap will be generated in the pure inductance circuits when the resonant frequencies are different in general. The locally resonant bandgap can be broadened by adding more resonators into the unit cell with the resonant frequencies of the shunting circuits satisfying a proper ratio.

Measurement of Proton Conductivity and Water Diffusivity of Nafion Membrane at Subzero Temperatures

Objective of this study is to obtain the water transport characteristics of Nafion at subzero temperature for automotive application. To achieve this objective, three different properties of the membrane are quantified: water content, proton conductivity, and diffusivity. Water content is computed from measuring the difference in weight between the dry membrane and humidified membrane at each relative humidity and subzero temperature. To measure the weight a special environmental cell was developed and integrated with the microbalance. To quantify the proton conductivity and the water diffusivity, a conductivity measurement electrochemical cell with segmented electrode is designed and fabricated to measure the high frequency resistance across the membrane at test conditions. An equation is developed for water content in terms of relative humidity and temperature. Equations for proton conductivity and water diffusion coefficient are presented in terms of water content and temperature. These equations are developed from experimental data obtained between 243K and 303K at different relative humidity.

Measurements of an AC-LGAD strip sensor with a 120 GeV proton beam

The development of detectors that provide high resolution in four dimensions has attracted wide-spread interest in the scientific community for several applications in high-energy physics, nuclear physics, medical imaging, mass spectroscopy as well as quantum information. LGAD silicon sensors with finely segmented AC-coupled electrodes can provide precise spatial and timing measurements of incident minimum ionizing particles. Such AC-coupled LGADs, also known as AC-LGADs, are therefore considered as candidates for future detectors to provide 4-dimensional measurements in a single sensing device with 100% fill factor. This article presents the first characterization of an AC-LGAD sensor with a proton beam of 120 GeV momentum at Fermilab. The sensor consists of strips with 80 μm width, fabricated at Brookhaven National Laboratory. The signal properties, efficiency, spatial, and time resolution are presented. The experimental results show that the time resolution of such an AC-LGAD is compatible to standard LGADs with similar gain, and that AC-LGADs can be segmented with fine pitches as standard strip or pixel detectors.

Reverse Electrodialysis: Co- and Counterflow Optimization of Multistage Configurations for Maximum Energy Efficiency.

Reverse electrodialysis (RED) is one of the techniques able to harvest energy from the salinity gradient between different salt solutions. There is a tradeoff between efficiency and generated power in a RED stack. This paper focuses on efficiency. A simple model is presented to calculate the efficiency in a co-flow or counterflow operated stack. Moreover, the efficiency can be improved by applying multistaging; the stacks in such a system can also be interconnected externally in co- and counterflow. The four combinations of internally and externally flow modes are the base of further considerations concerning procedures for optimization of these configurations. Three methods for optimization the energy efficiency in a multistage system are discussed: (A) successively maximizing the power of each individual stage, (B) maximizing the power of the whole system by adjusting the electrical current in all stages simultaneously, and (C) maximizing the power of the whole system by adjusting the same current through each stage. Method C is the most attractive because it only requires one converter (cheaper and easier to control) while the results are hardly inferior to B and much better than A. An alternative to multistaging is electrode segmentation and the advantages and disadvantages of both systems are briefly discussed.

P‐127: Multi‐touch Tactile Display with Segmented Electrode Structure and Driving Method for Presenting Tactile Free‐shape Localized Textures

We propose an electrostatic multi‐touch tactile display with a segmented electrode structure and electrode‐driving method for presentation of free‐shaped localized textures. This display solves the tactile crosstalk issue of our previously proposed tactile display. We evaluated the proposed display in a user test.

Electrode segmentation in reverse electrodialysis: Improved power and energy efficiency

Reverse electrodialysis harvests energy from salinity gradients establishing a renewable energy source. High energy efficiencies are fundamental to up-scale the process and to minimize feedwater pre-treatment and pumping costs. The present work investigates electrode segmentation to strategically optimize the output power density and energy efficiency. Electrode segmentation allows the current density to be tuned per electrode segment. Segmentation experiments were performed with a dedicated electrode configuration in a cross-flow stack using a wide range of residence times. Moreover, an experimentally validated model was extended and used to further compare single and segmented electrode configurations. While operating the electrode segments, the highest efficiencies were obtained when considering the overall power, i.e. not maximized by segment. Results show that at a given net power density (0.92 W·m−2), electrode segmentation increases the net energy efficiency from 17% to 25%, which is a relative increase of 43%. Plus, at 40% net energy efficiency the net power output for a segmented electrode configuration (0.67 W·m−2) is 39% higher than in a single electrode configuration. Higher power density reduces capital investment and higher energy efficiency reduces operating costs. Electrode segmentation increases these parameters compared to a single electrode and can be potentially applied for up-scaling.

3-D printed gradient porous composite electrodes improve anodic current distribution and performance in thermally regenerative flow battery for low-grade waste heat recovery

A thermally regenerative flow battery (TRB) with 3-D porous Cu/C composite electrodes is constructed and its anodic current distribution is investigated with 5 anode electrode segments. It is demonstrated that there is a markedly uneven current distribution in a TRB with uniform porous electrodes (TRB-M), thereby limiting the maximum power generation. The contribution of each electrode segment to the total current decreases along the flow direction due to the high resistance of mass transfer and the increased consumption of ammonia during the reaction. The gradient porous electrodes have a significant influence on the distribution of the anodic current and the power generation of the TRBs. A TRB using a gradient porous electrode with decreasing pore diameter (TRB-LS) results in a more uniform anodic current distribution and a 17% increase in the maximum power compared to that of a TRB-M. Further improvements in the current distribution and performance of a TRB-LS are made by increasing the concentration of ammonia and the electrolyte flow rate by effectively enhancing mass transfer.

Network segmentations of smart plate structure with attached mass and dynamic motions

This paper focuses on the primary development of novel analytical and numerical studies for the smart plate structure due to the effects of point mass locations, dynamic motions, and network segmentations. Instead of the alternative capabilities in active and passive control systems, the technical application of the present work can also be found in the energy harvesting system. The simplified theoretical studies have shown the simultaneous derivations with full variational parameters. In particular, these parameters consist of the mechanical and electromechanical systems, the mixed series–parallel electrode segment connection, and the harvesting circuit. The mechanical system parameters include elasticity with stress-strain relation, internal damping stress, air damping, and dynamics of the integrated physical system. The electromechanical system parameters include electrical displacement, electrical stress and electric-polarity field of the piezoelectricity. For the analytical approach, the governing equations of motion based on the Gram-Schmidt iterative process have been derived using the extended Hamiltonian principle and Ritz method-based weak form system. For validation, the electromechanical finite element equations reduced from the extended Lagrange’s equations have been developed using electromechanical discretisation and coupling transformation techniques. As a result, the two theoretical models have shown distinct frequency response equations for the dynamic solutions of the integrated physical system. In parametric studies, the two theoretical models of the smart plates with variable geometrical aspect ratio and different locations of point mass are discussed, giving good agreement. The strain mode analysis is utilised to identify the shape patterns at the region of the smart plate due to the change of strains. As a result, it can affect the electric power productions at the frequency domain. At certain cases, the appearance of asymmetric strain mode shapes may occur, resulting in the electric power reductions. To alleviate such condition, the activation of arbitrary electrode segments using the network connection can be implemented. Moreover, the smart structural model with different point mass locations is also subjected to the base excitation and the dynamic force. The proposed technique can adaptively and accumulatively generate the optimal power outputs and shift the resonance frequencies. All results of the parametric studies quantitatively show the dynamic system behaviours.

Electrostrictive PVDF-TrFE Thin Film Actuators for the Control of Adaptive Thin Shell Reflectors

This paper presents the technology to control the shape of thin polymer doubly curved shell structures with a unimorph layer of strain actuators to achieve high quality, light-weight, foldable space reflectors. The selected active material is PVDF-TrFE deposited by spin coating; it is electrostrictive, isotropic and enjoys an excellent piezoelectric coefficient d 31 ≃ 15 pC/N when properly annealed, but has a nonlinear, quadratic behavior. The strain actuation is controlled by an array of segmented electrodes. The purpose of this study is to evaluate the material properties achieved in the manufacturing process. A simple, unidirectional model of electrostrictive material is considered and the material constants (electrostrictive constant Q 33 , piezoelectric constant d 31 , spontaneous polarization P s and poling strain S P ) are estimated from various static and dynamic experiments. The final part of the paper illustrates the control authority on a small demonstrator with seven independent electrodes and compares the experimental results with numerical finite element simulations.

Signal-to-noise ratio enhanced electrode configurations for magnetoelectric cantilever sensors

Magnetoelectric cantilevers consisting of strain-coupled magnetostrictive and piezoelectric (PE) layers are applicable to magnetic-field sensing. For the first bending mode, the magnetic field-induced stress distribution is of equal sign along the cantilever length. Thus, a plate-capacitor electrode configuration encompassing the complete PE layer may be used for collecting the strain-induced charge. For higher order modes, stress regions of the opposite sign occur in the cantilever length direction. To prevent charge cancellation and to harvest the piezoelectric induced charge efficiently, segmented electrodes are employed. This study investigates the effect of the electrode configuration on the signal-to-noise ratio (SNR) for higher order bending modes. The charges collected by the electrodes are calculated using a finite element method simulation considering the mechanical, electrical, and magnetic properties of the cantilever. By combination with an analytic noise model, taking into account the sensor and amplifier noise sources, the SNR is obtained. We analyze a 3 mm long, 1 mm wide, and 50 μm thick silicon cantilever with layers of 2 μm magnetostrictive soft amorphous metal (FeCoSiB) and 2 μm piezoelectric aluminum nitride. We demonstrate that an SNR-optimized electrode design yields an SNR improvement by 2.3 dB and 2.4 dB for the second and third bending modes compared to a signal optimized design.

Influence of Electrode Interval and Barrier Thickness in the Segmented Electrode Micro-plasma DBD Reactor on CO2 Decomposition

In this paper, the decomposition of pure CO2 into CO and O2 were carried out in a segmented electrode DBD micro-plasma reactor at ambient pressure. With the assistance of gas chromatography, the influence of key factors like electrode interval and barrier thickness on the DBD filamentary behavior and CO2 decomposition process were investigated systematically. Meanwhile, the detailed electrical characterization during discharge process was also performed. The results indicated that a relatively higher CO2 conversion and energy efficiency could be obtained at the propitious condition of longer interval between adjacent electrodes and smaller barrier thickness, and the highest CO2 conversion and corresponding energy efficiency are 16.9% and 3.6%, respectively, at the condition of an applied voltage of 18 kV and 1.0 mm barrier thickness. Longer electrode interval can result in an increase in plasma density as well as enhance fringe effect. While the smaller barrier thickness, the smaller corresponding gas breakdown voltage, which meant that more electrical power was used for gas excitation. Accordingly, more energetic electrons were generated and more collisions between the electrons and CO2 molecules occurred. These were considered to be main reasons for enhanced CO2 decomposition process.

Comparing Current Steering Technologies for Directional Deep Brain Stimulation Using a Computational Model That Incorporates Heterogeneous Tissue Properties

ObjectiveA computational model that accounts for heterogeneous tissue properties was used to compare multiple independent current control (MICC), multi‐stim set (MSS), and concurrent activation (co‐activation) current steering technologies utilized in deep brain stimulation (DBS) on volume of tissue activated (VTA) and power consumption.MethodsA computational model was implemented in Sim4Life v4.0 with the multimodal image‐based detailed anatomical (MIDA) model, which accounts for heterogeneous tissue properties. A segmented DBS lead placed in the subthalamic nucleus (STN). Three milliamperes of current (with a 90 μs pseudo‐biphasic waveform) was distributed between two electrodes with various current splits. The laterality, directional accuracy, volume, and shape of the VTAs using MICC, MSS and co‐activation, and their power consumption were computed and compared.ResultsMICC, MSS, and coactivation resulted in less laterality of steering than single‐segment activation. Both MICC and MSS show directional inaccuracy (more pronounced with MSS) during radial current steering. Co‐activation showed greater directional accuracy than MICC and MSS at centerline between the two activated electrodes. MSS VTA volume was smaller and more compact with less current spread outside the active electrode plane than MICC VTA. There was no consistent pattern of power drain between MSS and MICC, but electrode co‐activation always used less power than either fractionating paradigm.ConclusionWhile current fractionalization technologies can achieve current steering between two segmented electrodes, this study shows that there are important limitations in accuracy and focus of tissue activation when tissue heterogeneity is accounted for.

A Computational Improvement in Grounding Systems Transient Analysis

This study investigates the adequacy of a modification in the evaluation of transversal and longitudinal impedance matrices for wideband modeling of grounding electrodes without a significant loss of accuracy. It is based on an approximation of the so-called hybrid electromagnetic model (HEM) and is called modified-HEM (MHEM). It exploits the average distance between segmented electrodes, allowing to pre-calculate the integral prior to the evaluation of the frequency loop improving considerably its numerical performance. Apart from some discrepancies for frequencies above a few MHz, the results for the harmonic impedance presented a very good accuracy when compared with the ones obtained using HEM. A comparison with an experimental test is carried out to enforce the adequacy of the investigated formulation within suitable parameters.

Direct current contact-mode triboelectric nanogenerators via systematic phase shifting

The intermittency and discontinuous nature of power generation in Triboelectric Nanogenerators (TENGs) are arguably their most significant drawback, despite the promise demonstrated in low-power electronics. Herein, we introduce a novel technology to overcome this issue, in which, built-in systematic phase shifting of multiple poles is used to design a pseudo direct-current TENG. Unlike previous attempts of constructing near direct-current TENGs that base on the segmentation of electrodes of a sliding mode TENG, this technology introduces a new method that depends on planned excitation of constituent TENG units at different time intervals to obtain the necessary phase shifts, achieved by their structural design that contains an asymmetric spatial arrangement. Therefore, the direct current generation for TENG, which was previously limited to the sliding mode TENG units, are expanded to contact-mode TENGs. The technology allows for continuous and smooth operation of the driven loads and paves the way for a new dawn in energy scavenging from mechanical sources. We use the distance-dependent electric field (DDEF) platform to design the systematic phase shifting technology, which is experimentally demonstrated via a free-standing mode TENG (FSTENG) based design, to power a number of prototype devices. The resultant power output of the TENG indicates a crest factor close to 1.1 at relatively low frequencies, the best reported values for TENGs with contact-mode basic units, to date. This work provides a highly awaited solution to overcome the intermittency and sporadic nature of TENG outputs, thus, promoting the field towards powering next generation autonomous and mobile electronics.

Fundamental electro-optic limitations of thin-film lithium niobate microring modulators

We investigate the impact of waveguide curvature on the electro-optic efficiency of microring resonators in thin-film X-cut or Y-cut lithium niobate (in-plane extraordinary axis) and derive explicit relations on the response. It is shown that such microring modulators have a fundamental upper bound on their electro-optic performance (∼50% filling factor) which corresponds to a specific arrangement of metal electrodes surrounding the microring and yields nearly identical results for X-cut and Y-cut designs. We further show that this limitation does not exist (i.e., 100% filling factor is possible) with Z-cut microring modulators or can be circumvented (i.e., ∼100% filling factor is possible) in X-cut and Y-cut modulators that use a race-track configuration with segmented electrodes. Comparison of our analytical results with multiphysics simulations and measured electro-optic efficiencies of microring resonators in the literature demonstrates the validity and accuracy of our approach.

Neural selectivity, efficiency, and dose equivalence in deep brain stimulation through pulse width tuning and segmented electrodes

BackgroundAchieving deep brain stimulation (DBS) dose equivalence is challenging, especially with pulse width tuning and directional contacts. Further, the precise effects of pulse width tuning are unknown, and recent reports of the effects of pulse width tuning on neural selectivity are at odds with classic biophysical studies. MethodsWe created multicompartment neuron models for two axon diameters and used finite element modeling to determine extracellular influence from standard and segmented electrodes. We analyzed axon activation profiles and calculated volumes of tissue activated. ResultsWe find that long pulse widths focus the stimulation effect on small, nearby fibers, suppressing distant white matter tract activation (responsible for some DBS side effects) and improving battery utilization when equivalent activation is maintained for small axons. Directional leads enable similar benefits to a greater degree. Reexamining previous reports of short pulse stimulation reducing side effects, we explore a possible alternate explanation: non-dose equivalent stimulation may have resulted in reduced spread of neural activation. Finally, using internal capsule avoidance as an example in the context of subthalamic stimulation, we present a patient-specific model to show how long pulse widths could help increase the biophysical therapeutic window. DiscussionWe find agreement with classic studies and predict that long pulse widths may focus the stimulation effect on small, nearby fibers and improve power consumption. While future pre-clinical and clinical work is necessary regarding pulse width tuning, it is clear that future studies must ensure dose equivalence, noting that energy- and charge-equivalent amplitudes do not result in equivalent spread of neural activation when changing pulse width.