Flat Plate Electrodes Research Articles

Treatment of heavy metal in the plating wastewater by electrocoagulation

Abstract This present paper evaluated a batch electrocoagulation (EC) scale containing two flat aluminium plate electrodes to treat total Cr, Zn2+ in real plating wastewater taken from CX Technology company. Response Surface Methodology (RSM) and Design-Expert 12 software were applied to optimize the operating conditions with three main factors including current density, pH, and retention time. The control experiments using FeSO4 10% were performed to compare with the electrocoagulation method. The best treatment efficiency occurred at a current density of 16.93 A/m2, pH 9, and a 31-minute reaction. The conductivity did not significantly affect to the total Cr and Zn2+ removal but reduced energy consumption. The jar-test experiment result was obvious the optimal factors of the coagulation-flocculation encompassing pH 10 and 3 ml/L FeSO4 10 %. The treatment efficiency of total Cr and Zn2+ were 97.22±0.3 % and 99.53± 0.006 %, higher than others. The generated sludge in the electrocoagulation method was 2,031± 0.91 g/L, equal to 51.7 % sludge of the coagulation-flocculation method. The treatment cost by electrocoagulation was less than others.

Pots to Plots: Microshock Weed Control Is an Effective and Energy Efficient Option in the Field

Seeking low environmental impact alternatives to chemical herbicides that can be integrated into a regenerative agriculture system, we developed and tested flat-plate electrode weeding equipment applying ultra-low-energy electric shocks to seedlings in the field. Better than 90% control was achieved for all species, with energy to treat 5 weeds m−2 equivalent to 15 kJ ha−1 for L. didymum and A. powellii, and 363 kJ ha−1 (leaf contact only) and 555kJ ha−1 (plants pressed to soil) for in-ground L. multiflorum, all well below our 1 MJ ha−1 target and a fraction of the energy required by any other weeding system. We compared applications to the leaves only or to leaves pressed against the soil surface, to seedlings growing outside in the ground and to plants growing in bags filled with the same soil. No previous studies have made such direct comparisons. Our research indicated that greenhouse and in-field results are comparable, other factors remaining constant. The in-ground, outdoor treatments were as effective and efficient as our previously published in-bag, greenhouse trials. The flat-plate system tested supports sustainable farming by providing ultra-low-energy weed control suitable for manual, robotic, or conventional deployment without recourse to tillage or chemical herbicides.

Simulation Analysis of Metallic Particles Movement in Typical Structure of Oil-immersed Power Transformer

The insulation performance of oil-immersed power transformers is closely involved with the movement of metal particle impurities, and the movement characteristics of metal particles are not only influenced by the electric field, but also by the oil flow. In this paper, a solid-liquid two-phase flow simulation model was constructed, and the effect of electric field on the motion of metal particles was considered. Firstly, the validity of the simulation model was verified by using the experimentally observed motion of metal particles in the horizontal oil channel between parallel flat plate electrodes, based on which the motion of metal particles in the typical oil channels of a 500kV power transformer was studied. It was found that when the metal particles passed through the oil flow inlet, the number of metal particles settling increased with the increase of particle size. All the metal particles with 1mm particle size sank in the oil flow inlet during the oil migration process, it was almost impossible to enter the low, medium and high voltage winding parts. Through the middle or upper end of the high voltage winding, the smaller particles (50μm, 150μm) would easily migrate with the oil flow and move faster; the larger particles (500μm) would move slower or be more easily deposited. This research holds significant practical implications in the engineering study of metal particle motion distribution within transformers.

Design and analysis of biconvex liquid lens with circular hole plate electrode structure

In this paper, based on the research of zoom liquid lens with parallel plate electrode and the principle of dielectrophoresis, a model of the biconvex liquid lens with circular hole plate electrode structure is proposed, which is a novel three-layer liquid lens structure. The dielectrophoretic effect refers to the phenomenon that free dielectric molecules will be polarized and moved by the force in a non-uniform electric field, thus deforming the dielectric liquid. In the dielectrophoretic liquid lens, only two insulating liquid materials with large refractive index difference and dielectric constant difference need to be selected, which can increase the selection range of liquid materials. The liquid lens structure mainly consists of a piece of double-sided conductive flat plate ITO glass with a circular hole and two pieces of single-sided conductive flat plate ITO glass, which respectively form two sets of flat electrode structures to control the upper interface and lower interface of the liquid droplet. In this structure, the influences of the intermediate glass plate on the focus and imaging are reduced by using the flat plate electrode with circular hole. The theoretical analysis of the structure is carried out with simulation software. Firstly, the models of the biconvex liquid lens with circular hole plate electrode under different voltages are built with Comsol software, the data of upper interface and lower interface of the liquid droplet are exported. Then by using Matlab, the surface shapes of the upper interface and lower interface of the droplet are fitted and the corresponding aspheric coefficients are obtained. Finally, the optical models are built with Zemax software, the imaging optical paths and the variation range of focal length under different voltages are analyzed. On the basis of the simulation, the corresponding device is made, and the specific experimental analysis is carried out. The surface patterns of the upper interface and lower interfaces of the droplet of the biconvex liquid lens under different voltages are recorded, the focal length and imaging resolution of the liquid lens are measured. When the operating voltage is in a range of 0–260 V, the focal length varies from 23.8–17.5 mm, which is basically consistent with the simulation results (22.6–15.9 mm). The feasibility of the structure of the biconvex liquid lens with circular hole plate electrode structure is verified experimentally. The imaging resolution can reach 45.255 lp/mm. The results show that this proposed novel three-layer liquid structure of the biconvex liquid lens has the characteristics of simple structure, easy-to-realize and good imaging quality. Therefore, the research of this biconvex liquid lens can provide a new idea for expanding the high-resolution imaging research of liquid lenses and their applications.

The Electric Spatula: Killing Weeds with Pulsed Microshocks from a Flat-Plate Electrode

Seeking an easy-to-deploy, energy-efficient, non-herbicide weed control method, we tested a flat-plate electrode to apply pulsed electric microshocks (PMS) to a grass and four broadleaf weed species. The method can be deployed via a hand-held unit or as part of a fully automated system to control escape weeds in field crops. The effectiveness of the treatments and the relative energy discharges when applying similar electric doses to the plant leaves or to the plant when pressed to the soil with a flat-plate electrode were compared. The method killed only half of the treated Lolium multiflorum “Winter Star” plants, well below our target rate, but significantly reduced growth rates and indicated that effective treatment of <1.0 MJ ha−1 for treating five plants m−2 is possible. Polygonum aviculare L., Amaranthus powellii S. Wats., Amaranthus deflexus, and Solanum nitidibaccatum Bitter plants were successfully controlled, with the energy required to kill 100% of seedlings varying from 0.1 to 0.9 MJ ha−1, indicating that broadleaf weeds are more susceptible. This easily met our target effectiveness and efficiency goals. The discharged energy increased when the electrode pressed the plant to a dry soil surface rather than to the leaves only and increased further when the electrode pressed the plant to a wet soil surface.

Improvement of the conventional flat plate electrode: Application of filtered Pd@Ti electrode in the removal of toxic chlorinated PPCPs

In order to change the mass transfer efficiency of conventional flat plate electrodes in the catalytic process, a new filtered Pd@Ti electrode has been prepared. The results indicated that the filtered Pd@Ti electrode had the best removal efficiency of 99.59% on diclofenac (DCF) at the flux of 40.85 L/m2∙h-1. Compared to unfiltered Pd@Ti electrodes, the removal efficiency was 1.18 times higher, the current efficiency was 2.15 times higher and the cost of electricity was 69.05% lower. The electrocatalytic hydrodechlorination process of DCF by filtered Pd@Ti electrode mainly relies on indirect reductive dechlorination by H* adsorbed on the electrode surface. The removal efficiency of the filtered Pd@Ti electrode remained above 80% after six cycles. The removal mechanism and reaction pathway of filtered Pd@Ti electrode for dechlorination of different chlorinated PPCPs were proposed. Furthermore, the ecotoxicity of chlorinated PPCPs and their products were evaluated by using the toxicity estimation software tool (T.E.S.T.) model. This study confirmed the promising application of filtered Pd@Ti electrodes for the removal and detoxification of chlorinated PPCPs in wastewater.

Thermal boundary layer depletion in minichannels by electrohydrodynamic conduction pumping

The article presents a numerical analysis of two-dimensional laminar flow and heat transfer in a minichannel with flat plate electrode pairs periodically flushed to the bottom wall. The two-way coupled governing equations of flow, heat transfer, electric potential and charge conservation are solved using the opensource finite-volume framework of OpenFOAM. Two cases of the minichannel at completely horizontal (case A) and 90° bent (case B) configurations are considered. The inlet laminar flow with Reynolds number varying from 10 to 1000 has been taken into account. The applied electric potential is varied in three steps 0, 0.5 and 1 kV. Electrohydrodynamic (EHD) conduction pumping due to the residual conductivity of the working fluid and the electric-field enhanced dissociation of free charges generate vortices in the proximity of electrodes. The flow and thermal performance of the minichannel in the presence of EHD conduction induced vortices are quantified in terms of pressure drop, Nusselt number and a performance factor (which is a combined function of pressure drop and Nusselt number). The vortices generated by EHD conduction pumping phenomenon deplete the thermal boundary layer, aid mixing and enhance the heat transfer. The mean and local Nusselt numbers are notably increased with only a minimal raise in pressure drop. In both the configurations of the minichannel, the performance factor is greater than 1 for the entire parameter space considered in this study. However, the thermal boundary layer depletion and heat transfer enhancement is prominent at low Reynolds number flows. The maximum drop in performance factor from case A to case B is only 18.5%. Results of this study indicate that EHD conduction pumping is a potential technique to enhance heat transfer in minichannels with minimum additional power consumption.

Effect of Flow Distributor Configuration on the Hydrodynamics in a Multipurpose Flow Electrochemical Reactor: Numerical Analysis and Experimental Characterization Employing Digital Image Treatment

Electrochemical reactors with a flat parallel plate electrode configuration and diverse flow channel designs have been extensively used in the study of different electrochemical processes at lab and bench scales, and they have been scaled up for some electrosynthesis and energy-storage processes at semipilot and industrial levels. Progress in the electrochemical process applications demands the use of different computer and experimental-assisted techniques to design novel electrochemical reactors. The objective of this work is to evaluate the hydrodynamic performance of different electrochemical reactor designs and quantify their effect on velocity magnitude through numerical and experimental studies using computational techniques like computational fluid dynamics (CFD) and digital image treatment. For local velocity magnitude measurements, a digital imaging treatment, based on the use of an optical flow algorithm, to try the validation of velocity profiles obtained by CFD is implemented. This experimental technique determined reliably that the problems associated with the use of the empty channel in the flow pattern are mainly associated with high velocities and recirculation zones, which are not detected by CFD simulations in the first instance. Also, the findings associated with the velocity behavior using this proposed technique agreed with those obtained by the traditional experimental flow characterization technique like residence time distribution, nevertheless, further work will be needed to refine the measurements and perform its comparison with other most employed velocimetry techniques.

Design and analysis of the biconvex liquid lens with circular hole plate electrode structure

In this paper, based on the research of zoom liquid lens with parallel plate electrode and the principle of dielectrophoresis, a model of the biconvex liquid lens with circular hole plate electrode structure is proposed, which is a novel three-layer liquid lens structure. The dielectrophoretic effect refers to the phenomenon that free dielectric molecules will be polarized and moved by the force in a non-uniform electric field, thus deforming the dielectric liquid. In the dielectrophoretic liquid lens, only two insulating liquid materials with large refractive index difference and dielectric constant difference need to be selected, which can increase the selection range of liquid materials. The liquid lens structure mainly consists of a piece of double-sided conductive flat plate ITO glass with a circular hole and two pieces of single-sided conductive flat plate ITO glass, which respectively form two sets of flat electrode structures to control the upper and lower interfaces of the liquid droplet. In this structure, the influence of the intermediate glass plate on the focus and imaging is reduced by using the flat plate electrode with circular hole. The theoretical analysis of the structure is carried out with simulation software. Firstly, the models of the biconvex liquid lens with circular hole plate electrode under different voltages are built with Comsol software, the data of upper and lower interfaces of the liquid droplet are exported. Then by using Matlab, the surface shapes of the upper and lower interfaces of the droplet are fitted and the corresponding aspheric coefficients are obtained. Finally, the optical models are built with Zemax software, the imaging optical paths and the variation range of focal length under different voltages are analyzed. On the basis of the simulation, the corresponding device is manufactured, and the specific experimental analysis is carried out. The surface pattern of the upper and lower interfaces of the droplet of the biconvex liquid lens under different voltages are recorded, the focal length and imaging resolution of the liquid lens are measured. When the operating voltage is 0V-260V, the focal length varies from 23.8mm to 17.5mm, which is basically consistent with the simulation results(22.6mm-15.9mm). The feasibility of the structure of the biconvex liquid lens with circular hole plate electrode structure is verified by experiments. The imaging resolution can reach 45.255 lp/mm. The results show that this proposed novel three-layer liquid structure of the biconvex liquid lens has the characteristics of simple structure, easy to realize and good imaging quality. Therefore, the research of this biconvex liquid lens can provide a new idea for expanding the high-resolution imaging research of liquid lenses and their applications.

Moffatt eddies in electrohydrodynamics flows: numerical simulations and analyses

We study numerically a sequence of eddies in two-dimensional electrohydrodynamics (EHD) flows of a dielectric liquid, driven by an electric potential difference between a hyperbolic blade electrode and a flat plate electrode (or the blade–plate configuration). The electrically driven flow impinges on the plate to generate vortices, which resemble Moffatt eddies (Moffatt, J. Fluid Mech., vol. 18, 1964, pp. 1–18). Such a phenomenon in EHD was first reported in the experimental work of Perri et al. (J. Fluid Mech., vol. 900, 2020, A12). We conduct direct numerical simulations of the EHD flow with three Moffatt-type eddies in a large computational domain at moderate electric Rayleigh numbers ( $T$ , quantifying the strength of the electric field). The ratios of size and intensity of the adjacent eddies are examined, and they can be compared favourably to the theoretical prediction of Moffatt; interestingly, the quantitative comparison is remarkably accurate for the two eddies in the far field. Our investigation also shows that a larger $T$ strengthens the vortex intensity, and a stronger charge diffusion effect enlarges the vortex size. A sufficiently large $T$ can further result in an oscillating flow, consistent with the experimental observation. In addition, a global stability analysis of the steady blade–plate EHD flow is conducted. The global mode is characterised in detail at different values of $T$ . When $T$ is large, the confinement effect of the geometry in the centre region may lead to an increased oscillation frequency. This work contributes to the quantitative characterisation of the Moffatt-type eddies in EHD flows.

Impact of asymmetries in valences and diffusivities on the transport of a binary electrolyte in a charged cylindrical pore

Ion transport in porous media is present in a wealth of technologies, e.g., energy storage devices such as batteries and supercapacitors, and environmental technologies such as electrochemical carbon capture and capacitive deionization. Recent studies on flat plate electrodes have demonstrated that asymmetries in ions properties, such as valences and diffusivities, lead to intriguing and counter-intuitive physical phenomena. Yet, the consequences of such asymmetries to ion transport have seldom been explored in porous geometries. To bridge this knowledge gap, we employ direct numerical simulations to solve Poisson-Nernst-Planck equations inside a cylindrical pore for a binary electrolyte with arbitrary valences and diffusivities. Next, we conduct a perturbation expansion in the limit of small potential and derive equations for charge and salt transport under confinement. We obtain good agreement between the perturbation analysis and the direct numerical simulations. Our analysis reveals that the charge and the salt transport are coupled with each other. Further, the coupling between the charge and salt transport processes is enhanced by an increase in valence and diffusivity asymmetries of ions. We observe that the mismatch of the ionic diffusivities induces a non-trivial salt dynamics, producing either transient depletion or enhancement of salt in the pore. In the regime of high static-diffusion-layer conductance, we obtain an analytical solution to our perturbation model. The solution elucidates how electrolyte asymmetry induces two charging timescales that are set by the relative pore size. In the overlapping-double-layer regime, these timescales reduce to the diffusion times of each ion such that the transport of the two ions appears to be decoupled. Overall, our work underscores that the asymmetry in cation and anion diffusivities fundamentally alters the behavior of ionic transport inside a charged cylindrical pore and opens up new avenues of research on electrolyte transport in porous materials.

Corona discharge behavior in foggy environments with flat plate and fin plate electrodes

The corona discharge is widely used to charge fog droplets. However, there is a lack of an accurate description of the interaction between fog droplets and the corona discharge process. Discharge currents of the two wire-plate devices in two foggy environments were measured experimentally. It was found that fog droplets floating in the air restrained the corona discharge process, and the effect of fog droplets was more significant than that of humidity variation. The discharge current decreases with increasing fog concentration. In addition, the electrohydrodynamic flow enhances the flow near the collection electrode and prevents large droplets from hanging on the collection electrode. The experimental results demonstrate that the corona discharge behaviors for the two devices comprising two types of collection electrodes are similar. The numerical prediction agreed well with the experimental data when the contribution of the droplet charge to the voltage and ion charge density was considered.

A high output triboelectric nanogenerator integrated with wave-structure electrode for football monitoring

In recent years, the development of triboelectric nanogenerator (TENG) technology has made great progress. However, most of the work focuses on the improvement of triboelectric materials and the optimization of device structure. In this work, we introduced a novel triboelectric nanogenerator integrated with wave structure electrode (W-TENG). Compared to the TENG with traditional flat plate electrode, the W-TENG with wave structure electrode can achieve higher output performance. The maximum short-circuit current (Isc), transfer charge, and open-circuit voltage (Voc) of 2.56 μA, 29 nC, and 74 V were obtained at 300 N. Correspondingly, the instantaneous output power of W-TENG illustrates the maximum value of 0.94 mW at 6 Hz. In addition, the output voltage signal of W-TENG can clearly reflect the different postures in football, and the W-TENG can perform real-time football monitoring. This mechano-electrical energy harvester and the corresponding self-powered monitor can promote the intelligent sports development.

Cathode shape prediction for uniform electrochemical dissolution of array tools for ECDM applications

ABSTRACT The effect of various cathode shapes, i.e., flat-plate, conical, and spherical-shaped cathodes, on the electrochemical dissolution (ECD) behavior of the 3 × 3 area-array tool electrode is presented. The allowed variation in all tip heights is less than 30 μm. Initially, the finite element method (FEM) was used to predicts the reduction in size and heights of the 3 × 3 tips. The spherical shape cathode exhibited uniform current density distribution around the tips, resulting in the consistent dissolution for a longer time than other cathode shapes. Detailed experiments were also performed to predict the dissolution behavior. Experimental results confirmed a similar dissolution behavior. The flat-plate electrode was not suitable in the ECD of array tool electrodes as the difference between the outermost and central tip heights was more than 130 µm, while the difference was less than 30 µm with a spherical-shaped cathode. Electrochemical discharge machining (ECDM) was carried out using the area-array electrodes made by the spherical and flat plate cathodes. The energy channelized by the uniform tips during the ECDM resulted in uniform material removal beneath all the tips, resulting in consistent crater formation. In contrast, a single crater was formed when the non-uniform tips were used.

Low-temperature electrostatic precipitator with different electrode configurations under various operation conditions

In this work, a low-temperature electrostatic precipitator (ESP) experiment platform was established, and two different electrode configurations were compared under various operating parameters to obtain a method for increasing particle capture efficiency. Results show that, in the case of the rated current, the voltage is significantly affected by temperature variations. Concurrently, by appropriately reducing the flue gas flow velocity of the ESP, the charging time of the particles in the ESP flue can be increased, fully charging the particles and improving the collection efficiency. Moreover, experiments revealed that increasing the relative humidity during ESP operation will increase the particle migration velocity and collection efficiency. Finally, when the electrode configurations were changed from a flat collection plate and round electrode to a sharper needle electrode and a concave-convex structure BE plate, resultantly, all efficiencies exceeded 85% under the temperature range from 50 to 150 °C.

Rapid Impedance Spectroscopy for Monitoring Tissue Impedance, Temperature, and Treatment Outcome During Electroporation-Based Therapies.

Electroporation-based therapies (EBTs) employ high voltage pulsed electric fields (PEFs) to permeabilize tumor tissue; this results in changes in electrical properties detectable using electrical impedance spectroscopy (EIS). Currently, commercial potentiostats for EIS are limited by impedance spectrum acquisition time ( ∼10s); this timeframe is much larger than pulse periods used with EBTs ( ∼1s). In this study, we utilize rapid EIS techniques to develop a methodology for characterizing electroporation (EP) and thermal effects associated with high-frequency irreversible EP (H-FIRE) in real-time by monitoring inter-burst impedance changes. A charge-balanced, bipolar rectangular chirp signal is proposed for rapid EIS. Validation of rapid EIS measurements against a commercial potentiostat was conducted in potato tissue using flat-plate electrodes and thereafter for the measurement of impedance changes throughout IRE treatment. Flat-plate electrodes were then utilized to uniformly heat potato tissue; throughout high-voltage H-FIRE treatment, low-voltage inter-burst impedance measurements were used to continually monitor impedance change and to identify a frequency at which thermal effects are delineated from EP effects. Inter-burst impedance measurements (1.8 kHz - 4.93 MHz) were accomplished at 216 discrete frequencies. Impedance measurements at frequencies above ∼1MHz served to delineate thermal and EP effects in measured impedance. We demonstrate rapid-capture ( 1s) EIS which enables monitoring of inter-burst impedance in real-time. For the first time, we show impedance analysis at high frequencies can delineate thermal effects from EP effects in measured impedance. The proposed waveform demonstrates the potential to perform inter-burst EIS using PEFs compatible with existing pulse generator topologies.

Development of a Multi-Pulse Conductivity Model for Liver Tissue Treated With Pulsed Electric Fields.

Pulsed electric field treatment modalities typically utilize multiple pulses to permeabilize biological tissue. This electroporation process induces conductivity changes in the tissue, which are indicative of the extent of electroporation. In this study, we characterized the electroporation-induced conductivity changes using all treatment pulses instead of solely the first pulse as in conventional conductivity models. Rabbit liver tissue was employed to study the tissue conductivity changes caused by multiple, 100 μs pulses delivered through flat plate electrodes. Voltage and current data were recorded during treatment and used to calculate the tissue conductivity during the entire pulsing process. Temperature data were also recorded to quantify the contribution of Joule heating to the conductivity according to the tissue temperature coefficient. By fitting all these data to a modified Heaviside function, where the two turning points (E0, E1) and the increase factor (A) are the main parameters, we calculated the conductivity as a function of the electric field (E), where the parameters of the Heaviside function (A and E0) were functions of pulse number (N). With the resulting multi-factor conductivity model, a numerical electroporation simulation can predict the electrical current for multiple pulses more accurately than existing conductivity models. Moreover, the saturating behavior caused by electroporation can be explained by the saturation trends of the increase factor A in this model. The conductivity change induced by electroporation has a significant increase at about the first 30 pulses, then tends to saturate at 0.465 S/m. The proposed conductivity model can simulate the electroporation process more accurately than the conventional conductivity model. The electric field distribution computed using this model is essential for treatment planning in biomedical applications utilizing multiple pulsed electric fields, and the method proposed here, relating the pulse number to the conductivity through the variables in the Heaviside function, may be adapted to investigate the effect of other parameters, like pulse frequency and pulse width, on electroporation.

Diagnostic study and simulation of capacitive coupled RF plasma

Aiming at the discharge characteristics of radio frequency capacitively coupled (CCRF) plasma at moderate pressure and medium power, a one-dimensional plasma discharge model was established by using COMSOL software based on fluid model. The distribution law in plasma electron temperature and electron density were studied at the same pressure and different radio frequency input power with Ar gas as working gas. At the same time, a closed glass cavity and a flat plate electrode of the same size were designed and fabricated according to the simulation model. The effective current, voltage and emission spectrum of the discharge plasma were measured experimentally at different RF input power. The electron temperature and electron density of the plasma were calculated by the current-voltage relationship and the energy balance equation. The electron temperature and electron density of plasma were obtained by Boltzmann double-wire method. When the gas pressure was 250 Pa and the input power was 100~450 W, the plasma voltage and current showed a linear relationship. The electron density increased with the increase of the power, but the electron temperature did not change with the change of the power. At the same time, the accuracy of the experiment was further verified by simulation. In this paper, the discharge parameters of plasma at moderate pressure are preliminarily diagnosed by combining the equivalent circuit method, spectral method and numerical simulation method, and a combination of these three methods is proposed for experiment to make the experimental results more convincing and to provide a basis for further study of plasma characteristics.

Characterization of Nonlinearity and Dispersion in Tissue Impedance During High-Frequency Electroporation.

The use of high-voltage, high-frequency bipolar pulses (HFBPs) is an emerging electroporation-based therapy for the treatment of solid tumors. In this study, we quantify the extent of nonlinearity and dispersion during the HFBP treatment. We utilize flat-plate electrodes to capture the impedance of the porcine liver tissue during the delivery of a burst of HFBPs of widths 1 and 2 $\mu$s at different pulse amplitudes. Next, we fit the impedance data to a frequency-dependent parallel RC network to determine the conductivity and permittivity of the tissue as a function of frequency, for different applied electric fields. Finally, we present a simple model to approximate the field distribution in the tissue using the conductivity function at a frequency that could minimize the errors due to approximation with a nondispersive model. The conductivity/permittivity of the tissue was plotted as a function of frequency for different electric fields. It was found that the extent of dispersion reduces with higher applied electric field magnitudes. This is the first study to quantify dispersion and nonlinearity in the tissue during the HFBP treatment. The data have been used to predict the field distribution in a numerical model of the liver tissue utilizing two needle electrodes. The data and technique developed in this study to monitor the electrical properties of tissue during treatment can be used to generate treatment-planning models for future high-frequency electroporation therapies as well as provide insights regarding treatment effect.

A substrate-independent fabrication of hollow sphere arrays via template-assisted hydrothermal approach and their application in gas sensing

A substrate-independent fabrication of hollow sphere arrays on desired substrates were demonstrated based on sulfonated polystyrene sphere template-assisted hydrothermal approach. By using this approach, Fe2O3 mono/multilayer hollow sphere arrays with tunable shell thickness and sphere diameter have been successfully prepared. Specially, this approach is universal for many other materials, such as the metal oxide In2O3, NiO, Co3O4, MgO, ZnO, CuO and SnO2, and the organic semiconductor polyaniline. Moreover, we can control the deposition of these hollow sphere arrays on any desired substrate such as flexible, glass slide, silicon wafer and flat plate electrode, which is very important for their applications in many fields, such as gas sensing. As an example, the Fe2O3 monolayer hollow sphere array as gas sensor was investigated in detail. It was found that the Fe2O3 hollow sphere arrays-based sensor display enhanced sensing performances with easy controllability, nice repeatability, high sensitivity, high stability and high selectivity in certain conditions, superior to those prepared by other methods, such as brushing. Generally, the proposed template-assisted hydrothermal approach afforded a new facile and universal approach to fabricate mono/multilayer hollow sphere arrays on any substrate, which will show high advantages in applications due to the controllable in-situ growth of the materials on desired devices.