Electrode Width Research Articles

Dielectrophoretic separation of monocytes from cancer cells in a microfluidic chip using electrode pitch optimization.

This study proposes a microfluidic device capable of separating monocytes from a type of cancer cell that is called T-cell acute lymphoblastic leukemia (RPMI-8402) in a continuous flow using negative and positive dielectrophoretic forces. The use of both the hydrodynamic and dielectrophoretic forces allows the separation of RPMI-8402 from monocytes based on differences in their intrinsic electrical properties and sizes. The specific crossover frequencies of monocytes and RPMI-8402 cells have been obtained experimentally. The optimum ranges of electrode pitch-to-channel height ratio at the cross sections with different electrode widths have been generally calculated by numerical simulations of the gradients of the electric field intensities and calculation their effective values (root-mean-square). In the device, the cell sorting has been conducted empirically, and then, the separation performance has been evaluated by analyzing the images before and after dielectrophoretic forces applied to the cells. In this work, the design of a chip with 77μm gold-titanium electrode pitch was investigated to achieve high purity of monocytes of 95.2%. The proposed device can be used with relatively low applied voltages, as low as 16.5V (peak to peak). Thus, the design can be used in biomedical diagnosis and chemical analysis applications as a lab-on-chip platform. Also, it can be used for the separation of biological cells such as bacteria, RNA, DNA, and blood cells.

Simulation of Coplanar Proximity Charge Sensing Electrodes in CZT Detectors

The concept of applying proximity charge sensing electrodes to semiconductor radiation detectors is a novel technique that has distinct advantages over directly deposited electrodes. This paper evaluates the application of proximity charge sensing onto a CdZnTe (CZT) semiconductor crystal using ANSYS Maxwell simulation software to calculate the weighting potential across the detector depth, the weighting potential across the detector width, and the electric field (E) generated inside the detector volume for multiple designs. To accomplish this goal, several variables are studied in the simulated designs: (1) a high resistivity thin-film material that is applied to the detector proximity surface from the anode side, (2) an appropriate metal that acts as an Ohmic contact to dissipate generated charges on the CZT anode side, and finally (3) an insulating layer (dielectric) to isolate the CZT detector body from the proximity electrodes. The results of the generated weighting potentials for both directly deposited electrodes and proximity-sensing electrodes, having the same electrode width and pitch, have been quantitatively compared using a figure of merit (FOM). The FOM compares the weighting potential created by each simulated design for weighting potential uniformity and weighting potential similarity.

The distribution of OH in surface micro-discharge with different electrode widths by laser-induced fluorescence

Cold atmospheric plasma has been successfully applied in the field of biomedicine. One of the most pressing challenge is the development of plasma devices, for example, large-area application in wound healing. Surface micro-discharge device is one new type of dielectric barrier discharge design with desirable plasma features, such as homogeneity over a large surface area. In this study, two devices with electrode width varying from 0.25 to 1.00 mm were fabricated. The contribution focuses on the impact of the hexagonal mesh electrode width on the degree of uniformity of hydroxyl (OH) radicals in the downstream region and the OH transport efficiency. Accordingly, OH radicals were measured as an indicator by laser-induced fluorescence. Steady state measurements of OH perpendicular to the dielectric surface demonstrated that narrow electrode width could not offer a high degree of uniformity, and will reduce the transport efficiency of reactive species.

Analyzes the effect of temperature on characteristics of crude oil permittivity sensor based on Interdigital Capacitors (IDCs)

This study aims to analyze the effect of temperature on characteristics of crude oil permittivity sensor based on interdigital capacitors (IDCs), including linearity, repeatability and hysteresis. IDCs have been fabricated using the DC Magnetron Sputtering method in three designs with different electrode materials and the same electrode configuration. The electrode materials used silver (Ag), copper (Cu) and molybdenum (Mo) deposited on a FR-4 PCB substrate with a thickness of 1μm. The electrode configuration each design is 15 mm electrode length, 0.5 mm electrode width, 0.5 mm electrode distance and 40 electrodes number. The crude oil was tested at a temperature range of 30 - 70°C. The measurement system uses a PM6303A automatic RCL Meter at a frequency of 1 kHz. The sensor linearity test results showed an increase in the sensitivity value of the IDCs Ag, Mo and Cu sensors when the temperature was more than 50°C. The repeatability sensor test results showed that IDCs made from Ag had the highest measurement precision with a value of %repeatability is 2.5%. The hysteresis test results showed that the design IDCs made from Ag have high stability at high and low temperatures.

Dielectrophoretic 3D‐focusing for on‐chip flow cytometry

Model-based analysis of a dielectrophoretic microfluidic device for realising 3D-focusing is presented in this work. The electrode configuration is made up of several finite-sized planar electrodes positioned on either side of the microchannel's top and bottom surfaces; the electrodes on the top surface and bottom surface of the same side form a pair. The forces associated with inertia, buoyancy, gravity, and dielectrophoresis are included in the model. As per the model, it is possible to use the proposed device to achieve 3D-focusing at the desired location along the width of the microchannel. Also, the proposed device can achieve 3D-focusing irrespective of the type of micro-scale entity. Two parameters for quantifying the efficacy of the microfluidic device in achieving 3D-focusing are presented – horizontal and vertical focusing parameters. The model demonstrates that the radius of micro-scale entity, electrode/gap lengths, electrode width, microchannel height, number of electrodes, applied electric potentials, and volumetric flow rate influence horizontal and vertical focusing parameters. The mathematical model is thus useful in designing dielectrophoresis-based 3D-focusing with desired performance metrics for on-chip flow cytometry.

Investigation by simulation of the RF carpets for the transport of ions at atmospheric pressures.

Ion funnels, quadrupole, and multipole are well-known ion optic methods for transportation of ions. However, the methods are suitable for pressures below 30-40 Torr. The main loss of ions occurs in an inlet of mass spectrometer at atmospheric pressure. This work offers a focusing system, which employs a fine-structure electrode ion carpet. The focusing efficiency of fine-structure electrode was investigated by computer simulation methods and it was compared with theoretical estimation. The methods demonstrated good agreement with each other that promises a reliability of results. The authors found an optimal fine-structure electrode ion carpet configuration (electrodes width of 10 µm), which demonstrates suitable focusing efficiency and can be implemented in practice.

Excellent thermoelectric performance in weak-coupling molecular junctions with electrode doping and electrochemical gating

Excellent thermoelectric performance in molecular junctions requires a high power factor, a low thermal conductance, and a maximum figure of merit ( ZT ) near the Fermi level. In the present work, we used density functional theory in combination with a nonequilibrium Green’s function to investigate the thermoelectric performance of carbon chain-graphene junctions with both strong-coupling and weak-coupling contact between the electrodes and the molecules. The results revealed that a room temperature ZT of 4 could be obtained for the weak-coupling molecular junction, approximately one order of magnitude higher than that reached by the strong-coupling junction. The reason for this is that strong interfacial scattering suppresses most of the phonon modes in weak-coupling systems, resulting in ultralow phonon thermal conductance. The influence of electrode width, electrode doping, and electrochemical gating on the thermoelectric performance of the weak-coupling system was also investigated, and the results revealed that an excellent thermoelectric performance can be obtained near the Fermi level.

High-frequency vibration analysis of LiTaO3 piezoelectric plates excited by lateral electric fields produced by surface electrodes under viscous liquid loadings for sensing

In this work, the coupled thickness-shear and flexural vibrations of the LiTaO3 piezoelectric plates excited by lateral electric fields produced by surface electrodes under viscous liquid loadings are modeled and analyzed based on Mindlin’s plate theory. The influences of liquid properties on the admittance characteristics and frequency shifts of the piezoelectric bulk acoustic wave devices operate in the lateral field excitation (LFE) mode are examined. In addition, the effects of the structure parameters, such as the electrode gap width, electrode/plate mass ratio and the electrode width, on the frequency sensitivity are investigated. It is shown that with the increasing electrode/plate mass ratio R, the sensitivities of the device on liquid viscosity and density increase first and then decrease, there is a maximal sensitivity when R is with a certain value. The varying trends of the frequency shifts with various liquid properties and sensitivities with various structural parameters are verified by the FEM simulations. The results are crucial to obtain good vibration characteristics and sensitivities for liquid-phase LFE piezoelectric sensors by using LiTaO3 piezoelectric crystals.

Design, Modeling and Simulation of a Capacitive Size-Discriminating Particulate Matter Sensor for Personal Air Quality Monitoring

We applied the well-established thermophoretic effect to air quality monitoring. We developed a novel method for particulate matter distribution analysis in an in-flow capacitive detection device. The proposed Multiphysics model combines fluid dynamics of particulate matter influenced by thermophoresis with electric field variations in the active volume space of a charged coplanar interdigitated electrodes. The model allows to anticipate the effect of thermophoresis in separating particles of PM10 and PM2.5 size ranges into different streams from a single particle-entrained flow and provides an estimated value of sensitivity for capacitive PM detection. The model is described through the Finite Element Method from the main equations to the simulation run using COMSOL Multiphysics and validated by comparing the results with literature. We obtained high sensor sensitivity of up to 0.48 zF/particle as far as $18~\mu \text{m}$ from coplanar electrode surface using the Computational Fluid Dynamics and Heat Transfer, Electrostatics and Particle tracing modules. We compare results of the simulations for different particle positions, electrode width and inter-electrode spacing, then we use the results to identify optimal design parameters for a novel architecture of a PM detection system with high sensitivity down to PM2.5 single particles and embedded particle size discrimination by using $10~\mu \text{m}$ electrode width and $1\mu \text{m}$ inter-electrode spacing.

Evaluation and improvement of image sticking in in-plane switching liquid crystal display

Image sticking in liquid crystal display (LCD) can affect the display quality. The saturated residual direct current voltage (SRDCV) can be obtained by analyzing the change in the capacitance of LC cell under the direct current bias, through which image sticking can be evaluated. On this basis, the image sticking was evaluated in the in-plane switching (IPS) cell filled in the LC with negative dielectric anisotropy for different electrode structures, cell gaps (i.e. 3.8, 5.8, and 7.5 µm), and doping concentrations of γ-Fe2O3 nanoparticles (i.e. 0.068, 0.136, 0.204, and 0.272 wt%). The SRDCV decreases under the same conditions by adjusting the ratio of electrode width and electrode gap and it decreases with the cell gap increases. For the thickness of 3.8 µm, the SRDCV initially decreases and then increases as the doping concentration of γ-Fe2O3 nanoparticles increases; while for the thicknesses of 5.8 µm and 7.5 µm, the SRDCV decreases as the doping concentration of γ-Fe2O3 nanoparticles increases. The results show that the structure design of the IPS-LCD and the doping of nanoparticles can effectively improve image sticking and provide useful guidance for enhancing the display quality of LCD.

A single‐cell‐gap transflective blue‐phase liquid crystal display based on fringe in‐plane switching electrodes

AbstractA transflective blue‐phase liquid crystal display (TRBP‐LCD) based on fringe in‐plane switching (FIS) electrodes is proposed. The proposed structure generates combined fringe and in‐plane electric fields that cause more liquid crystal (LC) molecules to reorient almost in plane above and between the pixel electrodes. The fringe field is mainly generated in the transmissive (T) region, and the horizontal electric field is mainly generated in the reflective (R) region. By optimizing the width of the pixel electrodes and the gap between two adjacent pixel electrodes, the different electric field intensity in the T and R regions contribute to balance the optical phase retardation between the T and R regions. As a result, the proposed TRBP‐LCD exhibits a low operating voltage and high optical efficiency, while it preserves a relatively simple fabrication process.

Configurations of triangular prism and slit electrode pairs to enhance the performance of electro-conjugate fluid micropumps

Previously, electro-conjugate fluid (ECF) micropumps with triangular prism and slit electrode pairs (TPSEs) have been developed and utilized for various mechanical, optical, chemical, and biomedical applications. However, the structural parameters of TPSEs have been determined by trial-and-error rather than systematical analysis. To this end, we select four structural parameters (i.e. hole width of a slit electrode: w, hole depth of a slit electrode: t, tip angle of a triangular prism electrode: , and gap between the triangular prism electrode and slit one: d) and implement the optimization to investigate their effects on the characteristic performance of ECF micropumps mainly depending on the combination of MEMS fabrication and experimental validation. Firstly, as a supplementary means, the simulation analysis is conducted with just consideration of the electric field intensity generated by TPSEs. After MEMS fabrication, the characteristic performance is experimentally characterized by comprehensively considering the generated electric field intensity, the flow dynamics, and the defect of microfabrication. The results show that the designed ECF micropump can attain the maximal output power under an applied DC voltage of 2 kV at the conditions of the slit hole width w = 200 µm, the slit hole depth t = 200 µm, the triangular tip angle = 60°, and the electrode gap d =200 µm. This optimization of TPSEs offers the helpful design guidance of ECF micropumps with higher output performance and promotes their further widespread use.

Experimental study on micro electrochemical slab milling using disc tool electrode

In this study, a method of micro-electrochemical slab milling with disc electrode is proposed for fabricating micro-groove structures on the surface of the workpiece. The disc electrode is in-situ prepared by micro-WEDM and subsequently used for micro-electrochemical slab milling process. The effects of the main electrochemical parameters, such as electrode feed rate of disc electrode and pulse width of power generator, on the width of the micro grooves and surface quality on 304 stainless steel were discussed. Finally, a micro-groove with a groove width of 254μm and good surface quality has successfully processed using the disc tool electrode with edge width of 170μm and proper process parameters. The proposed method broadens the machining flexibility and capability of micro electrochemical machining technology.

What is the difference in ablation zone of multi-bipolar radiofrequency ablation between liver cirrhosis and normal liver background? – a prospective clinical study

Purpose To explore the differences in ablation zone between liver cirrhosis and normal liver background and investigate the effect of hepatic blood flow on ablation zone of RFA. Methods Between 2017 and 2019, 203 patients who had liver malignancies and underwent percutaneous RFA with Celon bipolar electrodes enrolled into this study. There were 90 patients had liver cirrhosis and 113 patients had normal liver background. They were 63 females and 140 males with average age of 59.0 ± 10.9 years old. Contrast-enhanced CT/MRI was used to evaluate the ablation zone in one month after RFA. The hepatic flow measurements on CDFI and CEUS were performed before RFA. Correlations between ablation zone versus hepatic flow were assessed using multiple linear regression analysis. Results The average ablation zone in cirrhotic liver was significantly larger than those in normal liver background with 3 cm tip of RF electrodes (length 3.5 ± 0.5 vs 3.1 ± 0.4 cm, p = 0.001; width 2.6 ± 0.3 vs 2.2 ± 0.3 cm, p < 0.001; thickness 2.5 ± 0.3 vs 2.0 ± 0.2 cm, p < 0.001). The similar result was found with three 4 cm tip of RF electrodes (width 3.6 ± 0.5 vs 3.1 ± 0.5 cm, p = 0.019; thickness 3.3 ± 0.5 vs 2.7 ± 0.5 cm, p = 0.002). The multiple linear regression analysis showed arrive time of hepatic vein and portal vein was statistically associated with ablation zone with 3 cm electrodes (p < 0.001, p = 0.001), but explained part of the variance (Adjusted R2=0.294, adjusted R2=0.212). Conclusion The ablation zones of RFA with multi-bipolar electrodes in liver cirrhosis were significantly larger than those in normal liver background, being up to 6 mm in thickness. The hepatic flow parameters partly contributed to the ablation zone.

Characterization and development of an electrical conductivity flow cell for the axial continuous phase fraction profiling of bulk multiphase flow

In this study, the electric field generated by axial ring electrode conductivity cells is investigated. It is shown that the geometric parameters of such cells (mainly electrode separation, diameter and width) have a large effect on the resulting electric field uniformness. To quantify this effect, a parameter termed the effective measurement volume (EMV) is introduced which quantifies the measurement volume within the conductivity cell that contains 90% of the total current, normalized to that of an ideal conductivity cell (which generates a uniform electric field). The effects of a conductivity cells EMV on bulk conductivity measurements are both simulated and experimentally confirmed for emulated annular two-phase flow conditions. The results show that measurements performed with conductivity cells of high EMV tend towards true void fraction values, whereas cells of low EMV tended towards larger measurement error. This is quantified in the sum of squared residuals of the measurement, where a conductivity cell with an EMV of 0.19 has a sum of squared residual that is 638.4 times larger than a cell with an EMV of 1.00. Understanding the limitations of geometric parameters, a new axial conductivity profiling sensor was developed that uses one pair of electric field generating electrodes, and multiple measurement electrodes to create an axial conductivity profile with an axial measurement resolution of 10 mm.

Impact of width and spacing of interdigitated electrode on impedance-based living cell monitoring studied by computer simulation

The 3D computer simulation based on the finite element method was performed to obtain the impedance in the presence/absence of adherent living cells. The sensitivity of the inter-digitated electrode was investigated by varying the width (W) and spacing (S) for different number of electrode fingers N. It was found that the peak sensitivity corresponding to W/S < 1 and W/S > 1 exhibited higher sensitivity than W/S = 1. However, the sensitivity was relatively large when W/S < 1. Furthermore, the slope of the peak sensitivity curve decreased with the increase in N, emphasizing the fact that it has greater impact on sensitivity than W/S. It is important to note that the peak sensitivity due to smaller electrode width results in higher sensitivity. Hence, the experimentalists are recommended to choose the smaller electrode geometry with smaller electrode width in order to realize better sensitivity in the presence of adherent cell.

Dynamic wear sensor array based on single-electrode triboelectric nanogenerators

Smart sensor is the foundation and core of intelligent manufacturing, which is developing for miniaturization, integration and self-powering. Here, we report an active sensor array based on single-electrode triboelectric nanogenerators (TENGs) for dynamic wear monitoring and positioning. The sensor unit is fabricated by embedding the electrode into the core-shell composite with polytetrafluoroethylene (PTFE) as the core and polymethylmethacrylate (PMMA) as the shell. The working mechanism and performances of the sensor unit with different parameters including the thickness of PTFE@PMMA layer, reciprocating frequency, sliding displacement, electrode width and the diameter of copper bar are systematically investigated and discussed. By integrating into the sensor array, the dynamic wear monitoring and positioning have been realized, which can be used to detect the wear states of multiple regions in the sliding bearing system. This work has extended the application of the TENGs to determine the wear states of polymer interface and may promote the great development of intelligent bearing.

Optimization of a flexible piezoelectric module structure based on a lead-free piezoceramic embedded in nanofiber composites

Abstract To realize flexible piezoelectric materials with energy harvesting properties and vibrational characteristics, a piezoelectric module structure based on a lead-free piezoceramic embedded in a nanofiber composite was optimized according to the electrode structure and the module array arrangement. Lead-free piezoceramic particles embedded in nanofiber composites were prepared by an electrospinning process and then modularized by adding upper and lower electrodes via lamination. The energy harvesting properties of the flexible piezoelectric single modules with electrode structures consisting of top and bottom electrodes or interdigitated electrodes with various electrode widths and electrode intervals were characterized according to the oscillation frequency and the bending motion. The displacement and vibrational mode shapes of the flexible single modules were analyzed using a laser scanning vibrometer. Based on the optimized electrode structures of the flexible single modules, flexible piezoelectric dual modules were fabricated according to x- and z-axis array arrangements and to serial and parallel connection methods. The energy harvesting properties were measured and structural health monitoring sensor tests were conducted for several simulated situations. Among the examined modules, the flexible piezoelectric dual module with a serially connected x-axis array showed the best performance. This work provides a new guideline for using module structure design to enhance the piezoelectric effect in flexible modules.

Model-based analysis of geometrical effects in microfluidic fuel cell with flow-through porous electrodes

Porous electrodes in microfluidic fuel cell (MFC) operate with nonuniform reaction rate. It is intriguing to improve the utilization degree of the porous electrodes. In this work, a three-dimensional computational model is developed for MFC with flow-through porous electrodes. Characteristics of the reaction rate distributions under different electrode geometries are examined. The results show that reaction rate varies noticeably along the electrode width direction, but minimally along the electrode length direction. High reaction rate region locates in the vicinity of the interface between the porous electrode and the middle channel. A relatively high aspect ratio, defined as the ratio of the electrode length to width, is beneficial to improve the utilization degree of the porous electrodes. Yet, concentration losses increase due to the decreased fluid velocity. Considering the cell performance, optimal electrode aspect ratios are derived for the anode and cathode, respectively.

An Investigation of Internal Quantum Efficiency of Bifacial Interdigitated Back Contact (IBC) Crystalline Silicon Solar Cell

In this article, we investigated the internal quantum efficiency (IQE) properties of n-type bifacial interdigitated back contact crystalline silicon solar cells using an IQE mapping system. In the cell structure, high and low IQE values were observed above the emitter and back surface field (BSF) regions. The IQE values above the BSF busbar were drastically reduced due to electrical shading loss. Line scan profiles at different wavelengths showed the detailed distribution of IQE values. The IQE values varied greatly depending not only on the difference between emitter and BSF regions but also on the rear side structure such as the electrode width and the distance between the emitter and BSF regions. On the other hand, the IQE spectra at over 950 nm improved by increasing the light absorbance ratio from the rear side. After module formation, the IQE spectra at short wavelengths were significantly reduced. The IQE properties were obtained from the front and rear sides. The difference in the short-circuit current between front side illumination and rear side illumination was mainly due to optical shading loss and carrier recombination loss at the BSF region. For a high cell efficiency, it is necessary to improve the passivation properties of the BSF region and optimize the electrode design.