High Voltage Pulse Research Articles

On the modes of nanosecond pulsed plasmas for combustion ignition of quiescent CH4-air mixtures

The effect of transient plasma modes on ignition kernel development are discussed here for a quiescent CH4-air combustion model system. A 10 ns high-voltage pulse was applied to a pin-to-pin electrode in lean fuel-air mixtures at room temperature and atmospheric pressure. High-impedance streamer, transient spark and low-impedance spark discharges were identified based on pulse waveforms of voltage and current. A sustained ignition kernel expansion was observed when the plasma discharge transitioned into a transient spark or spark discharge. The minimum ignition energy was obtained at the transient spark mode, which has less than a third of the energy or Coulomb transfer compared to the low-impedance spark. Employing repetitive 10-pulse sequence at 10 kHz, the lean-fuel limit was extended from an equivalence ratio of 0.6 for the single pulse ignition to 0.5. The use of repetitive pulses also allowed streamer breakdown or spark initiation to occur at a lower voltage.

Study on preparation and anti-sand erosion performance of thick DLC coating combined with FCVA deposition and HVP technology

To address the compatibility issues between the hardness and thickness of DLC coatings and to improve the erosion resistance of engine blades, a thick DLC coating was prepared using a combination of filter cathode vacuum arc (FCVA) deposition technology and high voltage pulse (HVP) technology. The prepared thick DLC coating exhibits low residual stress (1.79 ± 0.087 GPa) and high C-sp3 content (70.13 %), with a thickness and hardness of 18.46 μm and 51.07 ± 0.23 GPa, respectively. The results of anti-sand erosion tests indicate that the mass loss rates of DLC coating at the erosion angles of 45° and 90° are 4.44 × 10−3 mg/g and 1.99 × 10−2 mg/g, respectively. The good erosion resistance of thick DLC coatings is attributed to the consumption of residual impact energy by carbon cluster structures, which prevents the generation and propagation of cracks. Therefore, the thick and super-hard DLC coatings can be prepared by combining FCVA deposition technique with HVP technique, which has great potential applications in the aerospace industry.

Influence of Voltage Rising Time on the Characteristics of a Pulsed Discharge in Air in Contact with Water: Experimental and 2D Fluid Simulation Study

In the context of plasma–liquid interactions, the phase of discharge ignition is of great importance as it may influence the properties of the produced plasma. Herein, we investigated the influence of voltage rising time (τrise) on discharge ignition in air as well as on discharge propagation on the surface of water. Experimentally, τrise was adjusted to 0.1, 0.4, 0.6, and 0.8 kV/ns using a nanosecond high-voltage pulser, and discharges were characterized using voltage/current probes and an ICCD camera. Faster ignition, higher breakdown voltage, and greater discharge current (peak value) were observed at higher τrise. ICCD images revealed that higher τrise also promoted the formation of more filaments, with increased radial propagation over the water surface. To further understand these discharges, a previously developed 2D fluid model was used to simulate discharge ignition and propagation under various τrise conditions. The simulation provided the spatiotemporal evolution of the E-field, electron density, and surface charge density. The trend of the simulated position of the ionization front is similar to that observed experimentally. Furthermore, rapid vertical propagation (<1 ns) of the discharge towards the liquid surface was observed. As τrise increased, the velocity of discharge propagation towards the liquid increased. Higher τrise values also led to more charges in the ionization front propagating at the water surface. The discharge ceased to propagate when the charge number in the ionization front reached 0.5 × 108 charges, irrespective of the τrise value.

Nanosecond pulse electric field treatment initiates mitochondrial apoptosis pathway by inducing mitochondrial morphological changes in myocardial cells.

As an emerging myocardial ablation technique, the mechanism of nanosecond pulse electric field (nsPEF) ablation is currently less studied. Mitochondria are one of the important membrane structure organelles in cells, participating in numerous life activities within the cell. This study aimed to explore the morphological changes of mitochondria in living cells following nsPEF treatment. Myocardial cells were treated with a self-made solid-state LTD high-voltage nanosecond pulse generator with a pulse width of 100ns for 80 times. The changes in mitochondrial membrane potential and cell apoptosis in rat myocardial cells after nsPEFs were investigated using JC-1 assay kit, apoptosis double staining assay kit, and mitochondrial fluorescence probe. The results showed that after nsPEF treatment, the mitochondrial membrane potential decreased, apoptosis increased, and the average mitochondrial area decreased from 0.48 µm2 in live myocardial cells to 0.16 µm2. The average circumference ranges from 3.17µm dropped to 1.60µm. The shape factor decreased from 1.92 to 1.41. The aspect ratio has decreased from 2.16 to 1.59. nsPEF treatment induces changes in the morphology of myocardial cell mitochondria. Based on the results of mitochondrial membrane potential and apoptosis, it can be inferred that under this equipment and parameter conditions, nsPEF treatment first causes changes in mitochondrial morphology, and then initiates the mitochondrial apoptosis pathway, which may provide experimental basis for investigating the potential mechanism of nsPEF ablation of myocardial cells.

High-voltage pulse generator for time-of-flight mass spectrometry in electrospray thrusters.

Electrospray thrusters exhibit diverse operational modes based on the nature of ejected particles. Time-of-flight mass spectrometry is frequently employed to analyze the composition of the plume. This study introduces a novel converter-based bipolar high-voltage pulse generator aimed at producing synchronized bipolar high-voltage pulses with controllable voltage levels and frequencies, specifically tailored for the study of electrospray thrusters. The proposed topology generates bipolar high-voltage rails from a low-voltage power source through the forward-flyback with Cockcroft-Walton voltage multiplier topology. Subsequently, fast high-voltage MOSFETs are employed to generate high-voltage pulses. This paper outlines the operational principles and design methodologies of the pulse generator. Experimental verification corroborates its operational principles and functionalities, revealing that the pulse rise and fall times consistently remain below 30ns, while the voltage can be tuned within the range of 300-1000V. An electrospray thruster was employed to conduct a thorough and practical validation of the high-voltage pulse generator. This included generating time-of-flight curves and mass spectra of the plume, resulting in precise differentiation of all particles present.

Enhanced Dye Adsorption on Cold Plasma-Oxidized Multi-Walled Carbon Nanotubes: A Comparative Study.

The oxidation of multi-walled carbon nanotubes (MWCNTs) using cold plasma was investigated for their subsequent use as adsorbents for the removal of dyes from aqueous solutions. The properties of MWCNTs after plasma modification and their adsorption capacities were compared with pristine and chemically oxidized nanotubes. The modification process employed a reactor where plasma was generated through dielectric barrier discharges (DBD) powered by high-voltage nanosecond pulses. Various modification conditions were examined, such as processing time and pulse voltage amplitude. The degree of oxidation and the impact on the chemistry and structure of the nanotubes was investigated through various physicochemical and morphological characterization techniques (XPS, BET, TEM, etc.). Maximum oxidation (O/C = 0.09 from O/C = 0.02 for pristine MWCNTs) was achieved after 60 min of nanopulsed-DBD plasma treatment. Subsequently, the modified nanotubes were used as adsorbents for the removal of the dye methylene blue (MB) from water. The adsorption experiments examined the effects of contact time between the adsorbent and MB, as well as the initial dye concentration in water. The plasma-modified nanotubes exhibited high MB removal efficiency, with adsorption capacity proportional to the degree of oxidation. Notably, their adsorption capacity significantly increased compared to both pristine and chemically oxidized MWCNTs (~54% and ~9%, respectively). Finally, the kinetics and mechanism of the adsorption process were studied, with experimental data fitting well to the pseudo-second-order kinetic model and the Langmuir isotherm model. This study underscores the potential of plasma technology as a low-cost and environmentally friendly approach for material modification and water purification.

Effect of the electrode spacing on dynamic fracture behavior of red sandstone under high-voltage pulse discharge

High voltage pulse technology has broad application prospects in the field of rock fragmentation. Electrical breakdown experiments of red sandstone under the action of high-voltage pulse discharge (HVPD) at different electrode spacings were conducted. The current waveform was recorded using a Rogowski coil. The fracture process on the specimen surface was observed by using an ultra-high-speed camera. The stress wave generated by HVPD was obtained. The experimental results show that both the peak values of the current wave and the stress wave decrease with the increase of the electrode spacing. The surface fracture of the specimen is dominated by transverse fractures parallel to the electrode axis, accompanied by shorter vertical fractures that are perpendicular to the electrode axis. The numerical model is further established to elucidate the three-dimensional fracture process and mechanism of the specimens, and the influence of the electrode spacing on the degree of fracturing is expounded.

Controllable Double‐Emulsion Droplet Manipulation Actuated by a Triboelectric Nanogenerator

AbstractElectrically controlled droplet manipulation is attractive for lots of applications ranging from material synthesis and drug delivery. However, the present techniques using bulky and expensive power supplies to generate high‐voltage electrical signals are easy to cause electrode electrolysis, bubble formation in buffer solution, and are incapable for point‐of‐care testing. Herein, a novel and portable electrical method for self‐powered emulsion droplet core coalescence and release based on triboelectric nanogenerator (TENG) is presented. The electrical signal with a 2.25 kV open‐voltage and a 35 µA short‐circuit current can be conveniently generated via frictional electrification effect, and the harmful electrochemical reaction in solutions can be avoided. The high transient pulse voltage and stable sinusoidal signal between two electrodes in microfluidic device can generate a strong electric field, which causes apparent Maxwell electrical stresses at droplet interfaces and subsequently promotes the core coalescence and release of double‐emulsions. By adjusting the voltage magnitude, the core coalescence and release behaviors of double‐emulsion droplets can be controllably achieved, followed by the synthesis copper‐based metal–organic framework (Cu‐MOF) nanoparticles. Thus, this portable, effective and self‐powered droplet manipulation technique can be attractive for those droplet‐based applications.

Enhancing Rare Earth Element Recovery from Coal Ash Using High-Voltage Electrical Pulses and Citric Acid Leaching

The study investigates the application of high-voltage electrical pulses (HVEP) as a pretreatment to enhance the leaching efficiency of rare earth elements (REE) from coal ash (CA) produced from the combustion of Ekibastuz Basin coal in Almaty, Kazakhstan. HVEP treatment was applied to the finest (<40 µm) non-magnetic fraction of CA under controlled conditions, optimizing discharge current, voltage, and treatment duration. Leaching experiments with 1 M citric acid at various solid-to-liquid ratios, temperatures, and durations were conducted on both treated and untreated samples. Results indicated that HVEP-treated CA significantly improved REE recovery rates compared to untreated samples, with optimal conditions achieving 74% cerium, 79% yttrium, and 77% lanthanum recovery. The leaching of untreated CA under the specified conditions allowed no more than 28% REE to be extracted into the solution. The leaching process was found to follow first-order kinetics, with the chemical reaction of metal dissolution being the rate-limiting step.

Regulating the Distribution and Accumulation of Charged Molecules by Progressive Electroporation for Improved Intracellular Delivery.

The cell membrane separates the intracellular compartment from the extracellular environment, constraining exogenous molecules to enter the cell. Conventional electroporation typically employs high-voltage and short-duration pulses to facilitate the transmembrane transport of molecules impermeable to the membrane under natural conditions by creating temporary hydrophilic pores on the membrane. Electroporation not only enables the entry of exogenous molecules but also directs the intracellular distribution of the electric field. Recent advancements have markedly enhanced the efficiency of intracellular molecule delivery, achieved through the utilization of microstructures, microelectrodes, and surface modifications. However, little attention is paid to regulating the motion of molecules during and after passing through the membrane to improve delivery efficiency, resulting in an unsatisfactory delivery efficiency and high dose demand. Here, we proposed the strategy of regulating the motion of charged molecules during the delivery process by progressive electroporation (PEP), utilizing modulated electric fields. Efficient delivery of charged molecules with an expanded distribution and increased accumulation by PEP was demonstrated through numerical simulations and experimental results. The dose demand can be reduced by 10-40% depending on the size and charge of the molecules. We confirmed the safety of PEP for intracellular delivery in both short and long terms through cytotoxicity assays and transcriptome analysis. Overall, this work not only reveals the mechanism and effectiveness of PEP-enhanced intracellular delivery of charged molecules but also suggests the potential integration of field manipulation of molecular motion with surface modification techniques for biomedical applications such as cell engineering and sensitive cellular monitoring.

Growth Mechanism of Three-Dimensional Plasma Channels in High-Voltage Electric Pulse Rock Breaking

Growth Mechanism of Three-Dimensional Plasma Channels in High-Voltage Electric Pulse Rock Breaking

Experimental and numerical simulation research on shock wave rock-breaking by high voltage electric pulse

High-voltage electric pulse(HVEP) drilling technology has the advantages of high rock-breaking efficiency, green and non-polluting. Aiming at the importance of HVEP drilling technology in generating plasma channels, plasma shock waves, and rock-breaking pits, this paper carries out multi-physics field numerical simulations and indoor electric pulse breakdown experiments. This paper first constructs a two-dimensional numerical model of rock electric breakdown. The simulation of HVEP rock breaking, plasma channel and plasma shock wave is realized from the five-field coupling and combined with the wave control equations. The effects of different electrode shapes on the plasma channel, breakdown channel and shock wave are analyzed. Then, this paper designed an indoor HVEP rock-breaking experiment to investigate the influence of different electrode shapes on rock breakdown and plasma shock waves. The simulation and experimental results show that the indoor electric pulse breakdown experiment results are consistent with the simulation results; The plasma channels are formed by the ‘electrical damage’ through each other, and the secondary plasma channel is often generated inside the rock. The generation of the secondary plasma channel means that the rock fragmentation depth and the fragmentation area will be increased; The larger the contact area of the electrode bit with the rock, the larger the radius (volume) of the plasma channel and the smaller the amplitude of the plasma shock wave; The quadrangular electrode bits have the best rock-breaking effect and are recommended; The conical electrode bit has the most excellent dispersion in the statistical analysis of the electric pulse rock-breaking effect, and the stability of the rock-breaking effect is poor, so it is recommended to use it together with the composite drill bit; The cylindrical electrode bit has the best aggregation degree of electric pulse rock-breaking and the most stable rock-breaking effect.

Interplay between Electric Field Strength and Number of Short-Duration Pulses for Efficient Gene Electrotransfer.

Electroporation is a method that shows great promise as a non-viral approach for delivering genes by using high-voltage electric pulses to introduce DNA into cells to induce transient gene expression. This research aimed to evaluate the interplay between electric pulse intensity and 100 µs-duration pulse numbers as an outcome of gene electrotransfer efficacy and cell viability. Our results indicated a close relationship between pulse number and electric field strength regarding gene electrotransfer efficacy; higher electric pulse intensity resulted in fewer pulses needed to achieve the same gene electrotransfer efficacy. Subsequently, an increase in pulse number had a more negative impact on overall gene electrotransfer by significantly reducing cell viability. Based on our data, the best pulse parameters to transfect CHO cells with the pMax-GFP plasmid were using 5 HV square wave pulses of 1000 V/cm and 2 HV of 1600 V/cm, correspondingly resulting in 55 and 71% of transfected cells and maintaining 79 and 54% proliferating cells. This shows ESOPE-like 100 µs-duration pulse protocols can be used simultaneously to deliver cytotoxic drugs as well as immune response regulating genetically encoded cytokines.

New insights of selective rupture of synthetic sample under high voltage pulse discharge: A numerical simulation of electric field distribution

Herein, COMSOL Multiphysics is proposed to discuss the electric field distribution of synthetic sample during the high voltage pulse discharge crushing. The pulses number required for high voltage pulse discharge to crush the synthetic sample filled with magnetite is lower than that required for quartz-filled samples. The embedding mode that the magnetite is located on the central line between the high voltage electrode and the grounding electrode of the synthetic sample is most conducive to electrical breakdown of synthetic sample. The discharge channel developed along the magnetite edge and retains the complete crystal form of magnetite. Differences in dielectric constants are responsible for variations in electric field distribution. Magnetite alters the distribution state of electric field within synthetic samples to derive higher electric field intensity and more extensive areas with high electric field intensity. The peak electric field intensity at the interface of magnetite particles is higher than that of quartz. The presence of quartz particles hinders the development of certain discharge channels.

A cost-consequence analysis comparing three cardiac ablation strategies for the treatment of paroxysmal atrial fibrillation

Background and aims Cardiac ablation is a well-established method for treating atrial fibrillation (AF). Pulsed field ablation (PFA) is a non-thermal therapeutic alternative to radiofrequency ablation (RFA) and cryoballoon ablation (CRYO). PFA uses high-voltage electric pulses to target cells. The present analysis aims to quantify the costs, outcomes, and resources associated with these three ablation strategies for paroxysmal AF. Methods Real-world clinical data were prospectively collected during index hospitalization by three European medical centers (Belgium, Germany, the Netherlands) specialized in cardiac ablation. These data included procedure times (pre-procedural, skin-to-skin and post-procedural), resource use, and staff burden. Data regarding complications associated with each of the three treatment options and redo procedures were extracted from the literature. Costs were collected from hospital economic formularies and published cost databases. A cost-consequence model from the hospital perspective was built to estimate the impact of the three treatment options in terms of effectiveness and costs. Results Across the three centers, N = 91 patients were included over a period of 12 months. A significant difference was seen in pre-procedural time (mean ± SD, PFA: 13.6 ± 3.7 min, CRYO: 18.8 ± 6.6 min, RFA: 20.4 ± 6.4 min; p < .001). Procedural time (skin-to-skin) was also different across alternatives (PFA: 50.9 ± 22.4 min, CRYO: 74.5 ± 24.5 min, RFA: 140.2 ± 82.4 min; p < .0001). The model reported an overall cost of €216,535 per 100 patients treated with PFA, €301,510 per 100 patients treated with CRYO and €346,594 per 100 patients treated with RFA. Overall, the cumulative savings associated with PFA (excluding kit costs) were €850 and €1,301 per patient compared to CRYO and RFA, respectively. Conclusion PFA demonstrated shorter procedure time compared to CRYO and RFA. Model estimates indicate that these time savings result in cost savings for hospitals and reduce outlay on redo procedures. Clinical practice in individual hospitals varies and may impact the ability to transfer the results of this analysis to other settings.

Electrode structural effects on the mechanism of high-voltage pulse rock breaking

In the oil drilling process, drilling costs account for more than 50% of total E&P costs. High-voltage electric pulse rock breaking is an economical and effective rock-breaking method that has received widespread attention. At present, there is not much research on the influence of the shape of the electrode tip on high-voltage pulse rock breaking. This paper establishes a system of equations that control the electric breakdown field based on the changes in the electric field inside the rock. Then, using this model, we conducted simulation and laboratory experiments to understand how rocks break under different conditions, such as load voltages, electrode spacing, and electrode tip shapes. The results show that the volume of broken rock is directly related to the loading voltage. The best loading voltage range is between 200 and 220 kV. Increasing the spacing between electrodes helps break more rock, but if the electrode spacing is too large, it's hard to make a hole in the rock, and the rock won't break. An electrode spacing of around 35 mm is the best. The shape of different electrode tips directly affects the high-voltage pulse breaking effect. Hemispherical electrode tips are less favorable for rock breaking, while oval electrode tips are the best. The laboratory experiments and simulations give the same conclusions and verify the applicability and correctness of our model. This study aims to help design high-voltage electric pulse devices.

Boosting DNA vaccine power by lipid nanoparticles surface engineered with amphiphilic bioresorbable copolymer

Successful DNA vaccination generally requires the aid of either a viral vector within vaccine components or electroporation device into muscle or skin of the host. However, these systems come with certain obstacles, including limited transgene capacity, broad pre-existing immunity in humans, and substantial cell death caused by high voltage pulses, respectively. In this study, we repurposed the use of an amphiphilic bioresorbable copolymer (ABC), named PLA-PEG, as surface engineering agent that conciliates lipid nanoparticle (LNP) between stability during preparation and biocompatibility post-vaccination. The LNP carrier can be loaded with SARS-CoV-2 spike-specific DNA; in this form, the DNA-LNP is immunogenic in hamsters and elicits protective immunity following DNA-LNP vaccination against heterologous virus challenge or as a hybrid-type vaccine booster against SARS-CoV-2 variants. The data provide comprehensive information on the relationships between LNP composition, manufacturing process and vaccine efficacy. The outcomes of this study offer new insights into designing next-generation LNP formulations and pave the way for boosting vaccine power to combat existing and possible emerging infectious diseases/pathogens.

A Description and Safety Overview of Irreversible Electroporation for Prostate Tissue Ablation in Intermediate-Risk Prostate Cancer Patients: Preliminary Results from the PRESERVE Trial.

The PRESERVE study (NCT04972097) aims to evaluate the safety and effectiveness of the NanoKnife System to ablate prostate tissue in patients with intermediate-risk prostate cancer (PCa). The NanoKnife uses irreversible electroporation (IRE) to deliver high-voltage electrical pulses to change the permeability of cell membranes, leading to cell death. A total of 121 subjects with organ-confined PCa ≤ T2c, prostate-specific antigens (PSAs) ≤ 15 ng/mL, and a Gleason score of 3 + 4 or 4 + 3 underwent focal ablation of the index lesion. The primary endpoints included negative in-field biopsy and adverse event incidence, type, and severity through 12 months. At the time of analysis, the trial had completed accrual with preliminary follow-up available. Demographics, disease characteristics, procedural details, PSA responses, and adverse events (AEs) are presented. The median (IQR) age at screening was 67.0 (61.0-72.0) years and Gleason distribution 3 + 4 (80.2%) and 4 + 3 (19.8%). At 6 months, all patients with available data (n = 74) experienced a median (IQR) percent reduction in PSA of 67.6% (52.3-82.2%). Only ten subjects (8.3%) experienced a Grade 3 adverse event; five were procedure-related. No Grade ≥ 4 AEs were reported. This study supports prior findings that IRE prostate ablation with the NanoKnife System can be performed safely. Final results are required to fully assess oncological, functional, and safety outcomes.

Pulsed processing by cold plasma, applied to industrial emission control.

A promising pollution control technology is cold plasma driven chemical processing. The plasma is a pulsed electric gas discharge inside a near atmospheric-pressure-temperature reactor. The system is energized by a continuous stream of very short high-voltage pulses. The exhaust gas to be treated flows through the reactor. The methods applied involve the development of robust cold plasma systems, industrial applications and measuring technologies. Tests of the systems were performed at many industrial sites and involved control of airborne VOC (volatile organic compound) and odor. Electrical, chemical and odor measuring data were collected with state-of-the-art methods. To explain the test data an approximate solution of global reaction kinetics of pulsed plasma chemistry was developed. It involves the Lambert function and, for convenience, a simple approximation of it. The latter shows that the amount of removal, in good approximation, is a function of a single variable. This variable is electric plasma power divided by gas flow divided by input concentration. In the results sections we show that in some cases up to 99% of volatile pollution can be removed at an acceptable energy requirement. In the final sections we look into future efficiency enhancements by implementation of (sub)nanosecond pulsed plasma and solid state high-voltage technology and by integration with catalyst technology.

Properties of a High-Power Ion Beam with Particle Energy up to 1 MeV Obtained from a Plasma Created by a High-Voltage Pulse on a Graphite Cathode

Properties of a High-Power Ion Beam with Particle Energy up to 1 MeV Obtained from a Plasma Created by a High-Voltage Pulse on a Graphite Cathode