Electrode Shape Research Articles

A three-dimensional micro-electrode array for in-vitro neuronal interfacing

Objective. In this paper, we report on the development of an easy-to-fabricate three-dimensional Micro-Electrode Array (3D-MEA) specifically designed for brain-on-a-dish applications. Approach. The proposed device consists of pillar-shaped gold microelectrodes realized by electroplating directly on top of a standard MEA, making this approach highly versatile and convenient for batch fabrication. Moreover, with this simple technique, it is possible to obtain electrodes with a height of more than 100 µm onto different kind of substrates, ranging from glass to flexible plastic ones. Main results. This novel 3D-MEA structure has been validated with acute brain slices, successfully recording both epileptiform-like discharges (upon the administration of 4-AP), and electrically-evoked neuronal activity. The preliminary validation showed a substantial improvement in the signals amplitude with respect to both commercial and custom planar electrodes thanks to a better coupling offered by the peculiar shape of the three-dimensional electrodes. Significance. Beside the versatility of the fabrication approach, which allows to obtain 3D MEA devices onto both rigid and flexible substrates, the reported validation showed how the pillar approach can outperform standard planar MEA recordings in terms of signal amplitude. Moreover, thanks to the possibility of obtaining multi-level 3D structures within the same device, the proposed fabrication technique offers an interesting and flexible approach for the development of a new family of electrophysiological tools for 3D in vitro electrophysiology, in particular for acute brain slices and 3D neuronal cultures for brain-on-a-dish applications.

Study of printed polymeric flexible energy harvesting elements – impact of the electrode materials and patterns

In this paper is presented study of flexible pressure piezoelectric energy harvesting developed with an screen-printing of polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) ink on three different metal electrodes (silver, gold and aluminium) with three different topologies – rectangular, meander and side comb. The influence of the electrode type and pattern is studied in terms of polymer coating distribution and morphology, piezoelectric voltage generation and stability at multiple bending, as well as piezoelectric coefficient. The elements are studied at low mass loading of up to 100 g and frequency up to 50 Hz. They produce voltage between 916 and 362 mV from active area of 1 cm2 and piezoelectric polymer film of 3 μm, according to the electrode metal nature and shape. It was found that the silver electrode with meander shape is the optimal for electrical performance and mechanical stability giving superior piezoelectric coefficient of 0.332 V.m/N to the reported values and only 8.6 % decrease of the piezoelectric voltage at 1500 repeating bending cycles.

A flexible workflow for simulating transcranial electric stimulation in healthy and lesioned brains.

Simulating transcranial electric stimulation is actively researched as knowledge about the distribution of the electrical field is decisive for understanding the variability in the elicited stimulation effect. Several software pipelines comprehensively solve this task in an automated manner for standard use-cases. However, simulations for non-standard applications such as uncommon electrode shapes or the creation of head models from non-optimized T1-weighted imaging data and the inclusion of irregular structures are more difficult to accomplish. We address these limitations and suggest a comprehensive workflow to simulate transcranial electric stimulation based on open-source tools. The workflow covers the head model creation from MRI data, the electrode modeling, the modeling of anisotropic conductivity behavior of the white matter, the numerical simulation and visualization. Skin, skull, air cavities, cerebrospinal fluid, white matter, and gray matter are segmented semi-automatically from T1-weighted MR images. Electrodes of arbitrary number and shape can be modeled. The meshing of the head model is implemented in a way to preserve the feature edges of the electrodes and is free of topological restrictions of the considered structures of the head model. White matter anisotropy can be computed from diffusion-tensor imaging data. Our solver application was verified analytically and by contrasting the tDCS simulation results with that of other simulation pipelines (SimNIBS 3.0, ROAST 3.0). An agreement in both cases underlines the validity of our workflow. Our suggested solutions facilitate investigations of irregular structures in patients (e.g. lesions, implants) or new electrode types. For a coupled use of the described workflow, we provide documentation and disclose the full source code of the developed tools.

Multi-electrode Designed Shape for Small Scale Plasma Incinerator

Currently electronic waste has increased due to the growth of an industrial economy. Conventional method of waste destruction was to use burner that heats up and finally forming hydrocarbon to an atmosphere. Recently, plasma technology is an alternative method that has an efficiency and safe to use as a mean for waste destruction due to its higher temperature. This research is an improvement design of electrodes tip used for plasma head assembly using small scaled power supply. The designed shape and materials such as graphite, steel and tungsten were simulated and used to evaluate the generated plasma. In addition, electrode designed group were compared for a current density and current distribution from a simulation which will also determine for a plasma length, temperature and durability of material on actual experimental. Electrode shape was designed with sharp cornered that has cross sectional area indicated that it has highest current distribution at the tip of electrode surface. Based on the simulation results, the proposed designed electrode was capable of highest current density when compared with others. The simulated and experimental results have been shown to agreed well for plasma length and temperature.

Shape design optimization of interdigitated electrodes for maximal electro-adhesion forces

We present a shape design optimization method for interdigitated electrodes in an electro-adhesive device. In the finite element analysis of electrostatics using linear basis functions, a finite node displacement method is used for the accurate electro-adhesive force by integrating the electric field along the boundary surface. The floating potential boundary for conductive objects is handled by a charge conservation law in the electrostatic analysis as well as the shape design sensitivity analysis. In numerical examples, the structural shape of interdigitated electrodes is optimized to maximize the electro-adhesion force per unit area for both conductive and non-conductive objects. It turns out that the electro-adhesive force is mainly induced by an electrostatic induction for conductive objects and by an electric polarization for non-conductive ones. There is an optimal ratio of electrode width and air gap thickness for non-conductive objects but no limit for conductive objects.

Geometry Optimization of Porous Electrode for Lithium-Ion Batteries

Since the invention of lithium-ion batteries about 40 years ago, the electrodes have been manufactured in essentially the same way: granulating active materials into powder and pasting them on conductive substrate with some additives such as carbon black and binder. Most optimizations have been focusing on tuning parameters such as particle sizes, porosity and electrode thickness, with the assumption of a uniform electrode. Recently some work demonstrated better cell performance by engineering the shape of the electrode with features such as nano cylinders, tunnels and fractal branches. On the simulation side, however, to the best of our knowledge, there has been no report on freeform electrode shape optimization: all current shape optimizations assume a particular electrode pattern with a few adjustable dimensional parameters, and optimize those parameters. Here we report a method to optimize the topology of the porous electrode without a prior assumption of the pattern. An NMC 333 electrode with lithium metal as the counter electrode is considered as an example. To find the optimal solid material distribution for maximum specific energy, we represented the NMC material distribution by 5-by-5 nodal design variables. To solve this 25-dimensional optimization problem, we integrated Deep Neural Network (DNN) into Generalized Simulated Annealing (GSA). During the optimization process, the DNN learns the objective function in real time with training data generated from finite element calculations. GSA uses the DNN to iteratively calculate the optimal solution and generates new training samples based on current optimal geometry to provide feedback to better train the network for further refinement. We show that the method can produce an electrode pattern with the specific energy about 18% higher than that of the uniform electrode. This generic geometry optimization approach provides a powerful tool for the design and optimization of porous electrodes. Figure 1

Fabrication of silicon electrodes used for micro electrochemical machining

In micro electrochemical machining (ECM), stray corrosion always causes undesired material dissolution and deteriorates the machining localization. Adopting sidewall insulating films on the electrode is proven to be an effective approach for reducing stray corrosion. Sidewall films with characteristics of good insulation, thin thickness, and excellent durability are required. In previous work, we proposed a heavily-doped silicon electrode, on which silicon-based films were prepared and acted as the insulating films. To fabricate silicon electrodes, this research investigates wet etching behavior of heavily doped Si (100) and then presents a fabrication process. Firstly, shapes of micro electrodes are designed on photomasks of lithography. Aiming at patterned profiles, effects of etchants on etch rate, dimension accuracy and surface integrity are investigated. Experimental results indicate that tetramethylammonium hydroxide (TMAH) leads to smoother electrode surfaces and fewer defects compared with potassium hydroxide. Then, insulation and durability performances of silicon-based films are investigated. 500 nm SiO2 and 300 nm Si3N4 composite film achieves more durable insulation and excellent compactness. Consequently, silicon electrodes with the dimension of 86 × 54 μm are fabricated on the Si (100) wafer with 25 wt% TMAH etchant, on which SiO2 and Si3N4 film is deposited by low-pressure chemical vapor deposition. In ECM experiments, stray corrosion of the non-machined surface is significantly reduced, and the sidewall taper of the machined structure is reduced to 5.5°. The validity and durability of silicon electrodes for micro ECM processes are verified.

Experimental and numerical analyses of electro-pulse rock-breaking drilling

The electro-pulse boring (EPB) of deep and ultra-deep wells has great market prospects. It uses controllable energy and is pollution-free. In this paper, research into high-voltage short-pulse power supplies and EPB electrode bits is reviewed. The simulation model was established according to the common coaxial cylindrical structure of the electric pulse rock breaking bit. The effects of the electrode spacing and the shape of the high-voltage electrode on the electric pulse rock breaking were then studied. According to the simulation results, the maximum electrode spacing was determined and the shape of the high-voltage electrode was optimized. The electrode bits with 45- mm spacing and 25-mm spacing were designed. Numerical simulations of EPB using these two bit sizes were conducted in which the actual structure size of the electrode bits and rock physical parameters were used. Simulation revealed an electric field distortion in the rock due to naturally-occurring air gaps, which can enhance the internal electric field strength. An experimental EPB system based on a transformer-type pulse generator was then developed. Transformer oil was used as a drilling fluid and red sandstone was drilled. Electric breakdown of sandstone by 25-mm and 45-mm electrode bits was conducted at a voltage of 80 kV, which produced drilling diameters of 60 mm and 100 mm, respectively. According to the simulation analysis and experimental research of EPB, the effective technological parameters and the law of EPB were obtained, which provided theoretical and practical guidance for electrode bit design and the selection of drilling parameters in practical applications.

Characteristics of dust-collection efficiency and ozone emission by high-voltage electrode shape of electrostatic precipitator for subway tunnel environment

The air pollution level of particulate matters in subway tunnel environments is severe. The present study conducted experimental measurements and analyses on dust-collection efficiencies and ozone emission rates in a lab-scale wind tunnel to determine a high-voltage electrode shape suitable for an electrostatic precipitator to remove airborne particles in subway tunnels. Six high-voltage electrode shapes (saw-type, few-saw-type, short-saw-type, tree-type, wave-type, and spike-type) were tested. The results indicate that while breakdown voltage of the spike-type high-voltage electrode was 66 % of other electrode shapes, its dust-collection efficiency per unit voltage was similar to that of other electrode shapes. However, the dust-collection efficiency per unit of power in the spike-type high-voltage electrode was significantly low. Moreover, the wave-type high-voltage electrode shape had 20 % lower dust-collection efficiency than the saw-type and tree-type high-voltage electrode shapes under conditions of low voltage and high flow velocities. Ozone emission rates for all shapes increased proportionally to the electric current. However, ozone emission rates for each high-voltage electrode shape are varied as 12–23 μg/s per mA. The saw-type and tree-type high-voltage electrode shapes were superior in terms of dust collection, 90 % collection efficiency was shown at about 1.5 W/(m/s)2. The saw-type had a lower ozone emission rate (16.4 μg/s per mA) than the tree-type (19.6 μg/s per mA). Thus, the saw-type shape was the most suitable as a high-voltage electrode in the electrostatic precipitator for removing airborne particles in a subway. The results also indicate that both dust-collection efficiencies and ozone emission rates should be evaluated concurrently when evaluating electrostatic precipitator high-voltage electrodes.

Studying Knotless Screen Patterns for Fine-line Screen Printing of Si-Solar Cells

Flatbed screen printing is the dominating process in industry for metallization of silicon solar cells. It offers high throughput rates, high flexibility of printing pattern, and an overall very cost-effective production compared with other printing technologies. However, the ongoing demand for an optimization of printed silver electrode shape creates an increasing challenge to paste and screen development. The recent trend of so called “knotless” screens with a screen angle of 0° offers an increased paste transfer, therefore, better electrode conductivity, which leads to an improved solar cell efficiency. The disadvantage of this screen architecture is a reduced screen lifetime and low production yield. This article presents a systematic simulation of screen pattern to investigate screen angles, which allow for an improved knotless screen architecture. Therefore, different types of wire crossings have been defined, simulated, and experimentally verified by microscope images. For example, when 14.036°, 18.435°, and 26.565° are used, knotless screen pattern openings emerge without showing any of the disadvantages of regular 0°-knotless screens. For this reason, statistical screen lifetime estimations are carried out by modeling the intersection lengths of all mesh wires and the emulsion edge across the screen opening. Furthermore, a detailed analysis on manufacturing tolerances is given, showing that the 26.565° screen angle offers the best compromise between challenges during manufacturing and potential performance in production of Si-solar cells.

Effects of process parameter on performance measures in electrical discharge machining using copper and brass electrodes

In the study of modern-day technology, it’s performance and parameters are evaluated using the EDM process in the drilling of stainless steel 316 material. SS316 material is widely used in many industrial applications such as heat transfer process and chemical tank. This test involves testing more material removal rate, improving the material hardness, reducing the electrode wear rate and machining time. The experiment is based on Taguchi L18 orthogonal array with 6 levels and 6 parameters like current, dielectric pressure, electrode shape, spark gap, polarity, pulse on and off time. Comparison of copper and brass electrodes in this experiment research is being conducted on how copper electrodes behave differently and exhibit better mechanical performance than brass electrodes. Brass electrode, with its high electrical resistance, low melting point and low thermal conductivity, copper has better performance than brass electrode and the different experimental levels and conditions are investigated.

МАТЕМАТИЧНІ МОДЕЛІ РОЗПОДІЛУ ГУСТИНИ СТРУМУ ВИСОКОЇ ЧАСТОТИ В ЕЛЕКТРОДАХ З РІЗНИМИ ФОРМАМИ ПОПЕРЕЧНОГО ПЕРЕРІЗУ

In the environment of mathematical package Matlab the analysis of high frequency current density distribution in electrodes of electrosurgical instruments is made. The results of calculations of one-dimensional and two-dimensional problems are presented, which model the skin-effect thickness in conductors with different cross-sectional shape. New structural shapes of electrodes for high-frequency surgery are proposed, which make it possible to distribute the current evenly over their contact surfaces

Optimal Lead Position in Patch-Type Monitoring Sensors for Reconstructing 12-Lead ECG Signals with Universal Transformation Coefficient.

The aim of this study was to reconstruct a 12-lead electrocardiograph (ECG) with a universal transformation coefficient and find the appropriate electrode position and shape for designing a patch-type ECG sensor. A 35-channel ECG monitoring system was developed, and 14 subjects were recruited for the experiment. A feedforward neural network with one hidden layer was applied to train the transformation coefficient. Three electrode shapes (5 cm × 5 cm square, 10 cm × 10 cm square, and right-angled triangle) were considered for the patch-type ECG sensor. The mean correlation coefficient (CC) and minimum CC methods were applied to evaluate the reconstruction performance. The average CCs between the standard 12-lead ECG and reconstructed 12-lead ECG were 0.860, 0.893, and 0.893 for a 5 cm × 5 cm square, 10 cm × 10 cm square, and right-angled triangle shape. The right-angled triangle showed the highest performance among the considered shapes. The results also suggested that the bottom of the central area of the chest was the most suitable position for attaching the patch-type ECG sensor.

Surface domain engineering in lithium niobate

In this work, we present a systematic experimental study of surface electric field poling for creating periodically poled lithium niobate. We want to control the homogeneity and the duty cycle of the periodic structures as well as domain shape and size in general. The created domain patterns are analyzed by selective etching with subsequent scanning electron microscopy. We investigate theoretically and experimentally how the shape of electrodes influences the poling results. Furthermore, the influence of the temporal waveform and magnitude of the applied poling voltage pulse is studied. Our results enable to identify optimal experimental parameters for high-quality surface poling.

Comparison of argon injection and other methods of electrovortex flow control in metallurgical furnaces

The article considers the problem of modeling the metal melting in a direct current arc furnace with the bottom electrode. A mathematical model and a technique for conducting coupled modeling of magnetohydro- and thermodynamic flows in such a furnace are presented taking into account electromagnetic forces and convection. Using the developed strategy, simulations were performed and the effectiveness of some approaches to the vortex flow control was evaluated. As a result, it was shown that changing the location, shape, and temperature of the bottom electrode as well as the bottom position can significantly reduce fettle wearing near the electrode, while argon injection does not decrease shear stress and does a negative influence on the fettle.

Dielectrophoretic microfluidic device for separation of red blood cells and platelets: a model-based study

The paper proposes a dielectrophoresis microfluidic chip for particle separation, which uses dielectric properties to perform size-based fractionation of red blood cells and platelets. Based on the control variables, the distribution of the electric field in the chip and the trajectory of the particles in the microfluidic channel are calculated using COMSOL Multiphysics under different electrode shapes, voltages and chip exit structures. Both red blood cells and platelets respond to negative dielectrophoresis at an alternating current signal with a frequency of 100 kHz. The larger red blood cells are subjected to a stronger dielectrophoretic force than the platelets and are biased toward the right outlet, and the platelets flow out from the left outlet under the combined action of fluid force and dielectrophoretic force to achieve the purpose of separation. On this basis, through quantitative comparison and analysis, a more optimized microfluidic chip capable of effectively separating particles is finally selected.

Continuum Sensitivity Analysis for Electrode Shape Optimization in Electrostatic System with State Variable Constraint

This article proposes an electrode shape optimization strategy with state variable constraints. The continuum sensitivity formula is used for the electrostatic system to determine the extremum of objective functions with state variable constraints. We use the gradient projection method and a restoration process to treat geometric and state variable constraints. The geometric changes of the design parameter are determined by the velocity field calculated from the constrained sensitivity analysis and are expressed by the level set method. The application models are tested to demonstrate the feasibility and utility of the proposed method.

Understanding the effects of different microstructural contributions in the electrochemical response of Nickel-based semiconductor electrodes with 3D hierarchical networks shapes

It is well known that exposed surface area, nanoparticles connectivity and its consolidation level in a nanostructure are key points in the enhancement of the electrochemical performance in energy storage devices. The design and optimization of different electrodes with specific microarchitectures (based on the arrangement manipulation of NiO nanoplatelets, used as building blocks), has allowed distinguishing the effects of each microstructural contribution in their final electrochemical responses, overpassing thermal and mechanical mismatches between the semiconductor ceramic structure and the metallic collector. In all cases, the same electroactive material and the same coating technique were used, preventing the interference of secondary phenomena in the EIS studies, and allowing argue over the contribution of the microstructural features incorporated to the electrode (nature and shape of the collector, degree of sintering and consolidation of the ceramic microstructure, incorporation of non-noble metallic nanoparticles and the macro/meso/microposity effect) in the effective profiting of the Faradaic phenomena observed during their cycling. The modification of the Ni-based electrodes allows understanding how microstructural features infer the electron transport and the ion diffusion through the consolidated structure. The EIS analysis proves that the design of the porous hierarchical network of our semiconductors electrodes resulted in a good rate capability (with capacitance values of 1000 F g−1 or 500 C g−1), exhibiting a relaxation time constant (τ0 = 18 ms), while a slight increase of the charge-transfer resistance (Rct = 3.65Ω) is negligible if the exposed surface is high enough to maintain a high ion transport. The inclusion of non-noble nanoparticles, such as Ni NPs, in the NiO semiconductor microstructure and the optimum deposited mass and sintering treatment create a metal-ceramic electrode that enhances both the charge transfer resistance (1.55 Ω) showing relaxation time in the range (τ0 = 11 ms) and maintaining an excellent capacitive behavior (750 F g−1 or 375C g−1) at quick charge/discharge rate.

Microelectrode Studies of S-NDR Copper Electrodeposition: Potentiodynamic and Galvanodynamic Measurements and Simulations

Copper electrodeposition from a CuSO4—H2SO4 electrolyte containing a polyether suppressor and (0 to 100) μmol∙L−1 Cl− is examined using a 25 μm diameter microdisk electrode. Optical imaging during cyclic voltammetry and galvanodynamic measurements reveal hysteresis, overpotential inversions, and the morphological evolution accompanying breakdown of the polyether-chloride inhibition layer. Simulations involving co-adsorption of the suppressor-halide adlayer and its subsequent breakdown capture the positive feedback and negative differential resistance (S-NDR) evident in electroanalytical measurements as well as important aspects of electrode shape evolution. The impact of electrode shape change on simulations of electroanalytical experiments is quantified in comparison to a stationary interface approximation. For potentiodynamic conditions, adlayer breakdown propagates rapidly from the center of the microelectrode surface although the final deposit profile is non-uniform due to enhanced transport to the disk perimeter. In contrast, galvanodynamic experiments in more concentrated Cl− solutions reveal spatially selective suppressor breakdown with deposition initially localized to the microelectrode center followed by outward expansion as applied current is increased. The difference between potentiodynamic and galvanodynamic responses reflects the convolution of S-NDR critical behavior with the respective control-loop load lines. Microelectrodes constrain or frustrate the otherwise random bifurcation process giving rise to predictable morphologies unattainable on macroscale electrodes.

Electronic Scanning Strategies in Adaptive Electrical Capacitance Volume Tomography: Tradeoffs and Prospects

Electrical Capacitance Volume Tomography (ECVT) has been applied for imaging of multiphase flows found in industrial applications. The ill-posed nature of the image reconstruction problem in ECVT and the consequent low resolution can be alleviated by employing electronic scanning enabled by electrode segmentation and reconfiguration during data acquisition. Here we study electronic scanning strategies that mimic physical rotation and shifting of the sensor along its symmetry axis. First, we study the feasibility of electronic scanning by analyzing the capacitance transducer circuit in SPICE. Then, we simulate electronic scanning using the finite element method for different electrode shapes, for which we compare the image reconstruction results and acquisition time. We find a noticeable improvement in image resolution for the scanning cases over conventional ECVT. Finally, among the scanning cases, we emphasize a particular electrode shape that provides the best image resolution along with the minimal amount of acquisition time.