Nanosecond Electrical Pulses Research Articles

Pulsed-field ablation-is it the only energy source for ablation in the future? : Pro/Contra

Pulsed field ablation (PFA) is anonthermal energy source used for cardiac ablation procedures. Cell death during PFA occurs via electroporation: ultrarapid (micro- to nanosecond) electrical pulses are applied to destabilize cell membranes causing irreversible pores. PFA leads to preferential ablation of myocardiocytes, sparing adjacent tissue like the esophagus or phrenic nerve. Preliminary clinical studies show high efficacy and agood safety profile in atrial fibrillation patients undergoing pulmonary vein isolation. The question remains, however, whether this new technology will replace well-known and established thermal energy sources like radiofrequency current or cryoablation within the next 5years.

Integrated Time Nanosecond Pulse Irreversible Electroporation (INSPIRE): Assessment of Dose, Temperature, and Voltage on Experimental and Clinical Treatment Outcomes.

This study sought to investigate a novel strategy using temperature-controlled delivery of nanosecond pulsed electric fields as an alternative to the 50-100 microsecond pulses used for irreversible electroporation. INSPIRE treatments were carried out at two temperatures in 3D tumor models using doses between 0.001 s and 0.1 s. The resulting treatment zones were quantified using viability staining and lethal electric field intensities were determined numerically. Computational modeling was then used to determine parameters necessary for INSPIRE treatments to achieve equivalent treatment zones to clinical electroporation treatments and evaluate the potential for these treatments to induce deleterious thermal damage. Lethal thresholds between 1109 and 709 V/cm were found for nominal 0.01 s treatments with pulses between 350 ns and 2000 ns at physiological temperatures. Further increases in dose resulted in significant decreases in lethal thresholds. Given these experimental results, treatment zones comparable to clinical electroporation are possible by increasing the dose and voltage used with nanosecond duration pulses. Temperature-controlled simulations indicate minimal thermal cell death while achieving equivalent treatment volumes to clinical electroporation. Nanosecond electrical pulses can achieve comparable outcomes to traditional electroporation provided sufficient electrical doses or voltages are applied. The use of temperature-controlled delivery may minimize thermal damage during treatment. Intense muscle stimulation and the need for cardiac gating have limited irreversible electroporation. Nanosecond pulses can alleviate these challenges, but traditionally have produced significantly smaller treatment zones. This study suggests that larger ablation volumes may be possible with the INSPIRE approach and that future in vivo studies are warranted.

Feasible Parameters of Ohmic Areas of YBaCuO Thin Films Switched via Moving Unstable Border between Superconducting and Normal States

A system of two equations based on one of the classical electricity laws was used to determine the sizes and temperatures of ohmic areas formed under action of overcritical nanosecond electrical pulses. Calculations were performed at five points for three experimentally obtained voltage–current (V-I) dependences for samples with the same geometry but different critical current density values. The system included two additional conditions to satisfy the known descriptive model of transition from superconducting (SC) to a normal (N) state—S-N switching—and to obtain physically acceptable solutions over the entire current range of V-I dependence. The solution for each point takes the form of a function, since the initial temperature increase of the primary channel across the film is entered as a parameter. Two modes of concentrated energy release in the channel were disclosed. Their random appearance leads to an unexpected degradation of the sample. As such, the obtained results correspond to the situations occurring during the experiments. The validity of applying additional conditions to the system is discussed. In the discussion, it is also explained at which moments the moving S-N border acquires the velocity of the order of ~106 m/s, comparable to the Fermi velocity. Consideration to describe the moving unstable S-N border as being constantly in a state of Richtmyer–Meshkov instability is presented.

Thermal Properties of Polymer Hole-Transport Layers Influence the Efficiency Roll-off and Stability of Perovskite Light-Emitting Diodes.

While the performance of metal halide perovskite light-emitting diodes (PeLEDs) has rapidly improved in recent years, their stability remains a bottleneck to commercial realization. Here, we show that the thermal stability of polymer hole-transport layers (HTLs) used in PeLEDs represents an important factor influencing the external quantum efficiency (EQE) roll-off and device lifetime. We demonstrate a reduced EQE roll-off, a higher breakdown current density of approximately 6 A cm-2, a maximum radiance of 760 W sr-1 m-2, and a longer device lifetime for PeLEDs using polymer HTLs with high glass-transition temperatures. Furthermore, for devices driven by nanosecond electrical pulses, a record high radiance of 1.23 MW sr-1 m-2 and an EQE of approximately 1.92% at 14.6 kA cm-2 are achieved. Thermally stable polymer HTLs enable stable operation of PeLEDs that can sustain more than 11.7 million electrical pulses at 1 kA cm-2 before device failure.

Nanosecond bacteria inactivation realized by locally enhanced electric field treatment

Bacterial contamination in water is still a critical threat to public health; seeking efficient water disinfection approaches is of great significance. Here we show that locally enhanced electric field treatment (LEEFT) by electrodes modified with nanoscale tip structures can induce ultrafast bacteria inactivation with nanosecond electrical pulses. A lab-on-a-chip device with gold nanowedges on the electrodes is developed for an operando investigation. Attributed to the lightning-rod effect, the bacteria at the nanowedge tips are inactivated by electroporation. A single 20 ns pulse at 55 kV cm−1 has achieved 26.6% bacteria inactivation, with ten pulses at 40 kV cm−1 resulting in 95.1% inactivation. LEEFT lowers the applied electric field by about 8 fold or shortens the treatment time by at least 106 fold, compared with the system without nanowedges. Both Gram-positive and Gram-negative bacteria, including antibiotic-resistant bacteria, are inactivated with nanosecond pulses by LEEFT. According to simulation, when the membrane of the cell located at the nanowedge tip is directly charged by the concentrated charges at the tip, it is charged much faster and to a much higher level, leading to instant electroporation and cell inactivation. Efficient ways to disinfect water from bacterial contamination are essential for public health. Locally enhanced electric field treatment can be used to induce ultrafast bacteria inactivation with nanosecond electrical pulses.

Descriptive model of the transition from superconducting to normal state in thin high quality YBaCuO films by nanosecond electrical pulses

A descriptive model of normal zone (N-zone) propagation during the pulsed transition from superconducting to normal state (S-N switching) in the YBaCuO thin films is proposed. The model should explain the unexpected film damage. An ideal propagation of the N-zone was simulated using a combination of sinus-like functions, representing an unstable border between superconducting and normal states (S-N border). Plane geometry of the S film causes the concentration of current and expelled magnetic field at the film edges, which allows us to consider the S-N border as a separate object. Three cases, when the S-N border has effective penetration depth (λeff) of 2.45, 1.64, and 1.155 μm widths with accordingly different critical current densities and impact of coherent jets, are considered. To define numerical values of the S-N switching parameters, earlier obtained experimental parameters were taken. It was shown that the ideal propagation is insufficient to explain the damaging process. Based on the scanning electron microscope (SEM) images of damaged films, it is concluded that coherent jets and other magnetic hydrodynamics phenomena exist in the real N-zone propagation. During the propagation, closed S and N areas form and then are contracted, resulting in round dark spots visible in the SEM images. The conservation of the trapped magnetic flux is manifested during this contraction. Numerical calculations of contracting processes show that circular currents at λeff reach the Ginzburg-Landau de-pairing current densities. This explains the unexpected irreversible damage of the high quality thin YBaCuO films after the flash S-N switching.

Nanosecond-Pulsed Perovskite Light-Emitting Diodes at High Current Density.

While metal-halide perovskite light-emitting diodes (PeLEDs) hold the potential for a new generation of display and lighting technology, their slow operation speed and response time limit their application scope. Here, high-speed PeLEDs driven by nanosecond electrical pulses with a rise time of 1.2ns are reported with a maximum radiance of approximately 480 kW sr-1 m-2 at 8.3 kA cm-2 , and an external quantum efficiency (EQE) of 1% at approximately 10 kA cm-2 , through improved device configuration designs and material considerations. Enabled by the fast operation of PeLEDs, the temporal response provides access to transient charge carrier dynamics under electrical excitation, revealing several new electroluminescence quenching pathways. Finally, integrated distributed feedback (DFB) gratings are explored, which facilitate more directional light emission with a maximum radiance of approximately 1200 kW sr-1 m-2 at 8.5 kA cm-2 , a more than two-fold enhancement to forward radiation output.

Investigation of Effect of Nanosecond Pulsed Electric Field on MCF-7 Breast Cancer Cells

Pulsed electric field therapy is a novel non-invasive approach for cancer therapy. It serves as a cell permeability enhancing agent for cancer treatment. Nanosecond, high-electrical field pulse power technology is used for delivering variable, controllable, intracellular electrical perturbations in several biological systems. Here, we investigated the effect of nanosecond (ns) electric pulse (nsEP) as a therapeutic tool for cancer. In in-vitro study, the breast cancer cells (MCF-7) were exposed with electric field of ~18kV/cm intensity, ~25ns duration, at 1.5Hz in a 2mm electroporation cuvette. Post exposure, observation shows a significant reduction in cell viability. It was evident that after treatment the viability of MCF-7 cancer cells at 630 pulses are remains ~38% only. The optical microscopic analysis of MCF-7 cells shows cell morphology changes after electrical pulse exposure. Moreover, we have also investigated a comparative study of the effect nano-second electrical pulses on MCF-7 cells and Chinese Hamster Ovary (CHO) cell line. The comparative study, demonstrated that the effect of nsEPF on MCF-7 is more destructive than on CHO cell line. The obtained results support that the pulse electrical field of nanosecond (ns) duration therapy would be a potential solution for cancer treatment.
 Keywords: Nanosecond Pulse Electric Field; Full Width at Half Maxima; Pulse Forming Line; Pulse Exposure; Viability;

Parallel electrodes gliding plasma: Working principles and application in dry reforming of methane

A parallel electrodes gliding plasma (PEGP) is developed and applied for the dry reformation of methane. It consists of a pair of parallel wire-plate electrodes that is fed by repetitive nanosecond electrical pulses and placed into a divergent acoustic waveguide. The waveguide conducts the plasma-produced acoustic shock waves forward, causing sparking at the low pressure moving nodes of the waves. Consequently, PEGP provides a high plasma mobility within the volume of the parallel electrodes where constant reduced field (E/N), optimized for molecular dissociation, is applied. This is in contrast to the case of the conventional glide plasma, where E/N covers a range of values. Besides, the energy of the mobile plasma is mostly dissipated in the layers of fresh reactants gas, instead of overheating or dissociating the products. Consequently, higher conversion rates and energy efficiencies are obtained. The performances of PEGP and different pulsed plasmas, are examined and compared in this study. Conversion rates of almost 50% for both reactants (CO2, CH4) with ECE exceeding 70%, at temperature of about 100 °C, are provided by PEGP. The cold PEGP has comparable conversion performance with the high temperature thermal plasmas while performs much better compared to the other reported cold plasmas.

Synergistic effect of picosecond optical and nanosecond electrical pulses on dielectric breakdown in aqueous solutions

The combined effect of short (picosecond) optical and (nanosecond) electrical pulses on dielectric breakdown is investigated both theoretically and experimentally. It was demonstrated that nanosecond electrical pulses (nsEPs), being applied simultaneously with picosecond optical pulses, reduce the threshold for optical breakdown. Experimental results are discussed with respect to an extended model for opto-electrical-induced breakdown. The newly unveiled effect is expected to play a significant role in spatially confined electroporation and further advances in laser-ablation-based processes while also allowing for measurements of ambipolar diffusion constants.

Thermal nucleation and high-resolution imaging of submicrometer magnetic bubbles in thin thulium iron garnet films with perpendicular anisotropy

Nanometer-thin rare-earth iron garnet films with perpendicular magnetic anisotropy are among the most promising materials for fast and low-energy spintronics applications. Here, the authors demonstrate ultrafast control of intrinsically stabilized submicrometer bubble domains in these materials. By employing powerful x-ray imaging techniques both in transmission and with surface sensitivity, and by combining this with nanosecond electrical pulses and femtosecond laser excitation, they deterministically create, and image, these bubble states $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$. The topology, the chirality, and the switching phase diagram of these twisted spin structures are all resolved by direct imaging.

Analysis of Optical and Electrical Responses of $\boldsymbol{\mu}$ -OLED With Metallized ITO Coplanar Waveguide Electrodes Submitted to Nanosecond Electrical Pulses

In this paper, the optical and electrical pulse responses of an optimized high-speed organic light-emitting diode (OLED) is investigated as a function of the pulse duration. The original design is based on the coplanar waveguide electrodes that are implemented on a transparent and conductive oxide thin film. The designed electrodes with reduced serial resistances (13 $\Omega $ ) allow to maximize the pulse energy delivery and to feed the organic device with short electrical pulses of few nanoseconds for the first time. This is achieved by designing the electrodes to have 50- $\Omega $ characteristic impedance, thanks to microwave techniques, and by implementing small values of capacitance (4.5 pF). The experimental results demonstrate $\boldsymbol \mu $ -OLED electrical and optical responses to electrical excitation pulses as short as 2.5 ns, for the first time, and state-of-the-art current densities above 1.7 kA/cm2. Moreover, and rather unexpectedly, the developed characterization procedure to extract the reported results demonstrated the first direct measurement of the electroluminescence lifetime of organic materials in the nanosecond time scale.

Variations of Intracellular Ca2+ Mobilization Initiated by Nanosecond and Microsecond Electrical Pulses in HeLa Cells.

Herein, the variations in transient Ca2+ mobilizations in HeLa cells exposed to a single, non-thermal pulsed electric field (PEF) are described. Three PEF waveforms categorized by pulse duration and intensity were used to deduce the kinetics involved in Ca2+ mobilization. A fast microscopic fluorescent imaging system and a fluorescent molecular probe were used to observe transient intracellular Ca2+ mobilization after pulse exposure. The sources and pathways in the transient Ca2+ mobilizations were investigated using an inhibitor of inositol-1,4,5-trisphosphate receptor (IP3R) on the endoplasmic reticulum (ER) along with a Ca2+-free buffer. When exposed to the 10-μs-long PEF, the Ca2+ concentration increased mainly at the cathodic region near the membrane. However, Ca2+ concentration increased at both anodic and cathodic regions when Na+ concentration in the buffer was reduced. Ca2+ concentration increased only in the presence of extracellular Ca2+. These results suggest that the 10-μs PEF takes a large amount of extracellular Na+ into the cell through the electropermeabilized plasma membrane, especially at the anodic side, resulting in the suppression of the Ca2+ influx. On the contrary, the 20-ns-long PEF increased Ca2+ concentration in the surrounding region of the nucleus only in the presence of extracellular Ca2+. The PEF exposure with inhibition of the IP3R indicates that increased Ca2+ ions are released from the ER via the activated IP3R. These mechanisms could induce specific cell responses, such as Ca2+ oscillations, Ca2+ waves, and Ca2+ puffs.

Safe and Efficient siRNA Therapy using Nanosecond Laser and Electrical Pulses

Safe and Efficient siRNA Therapy using Nanosecond Laser and Electrical Pulses

Adult human dermal fibroblasts exposed to nanosecond electrical pulses exhibit genetic biomarkers of mechanical stress

BackgroundExposure of cells to very short (<1µs) electric pulses in the megavolt/meter range have been shown to cause a multitude of effects, both physical and molecular in nature. Physically, nanosecond electrical pulses (nsEP) can cause disruption of the plasma membrane, cellular swelling, shrinking and blebbing. Molecularly, nsEP have been shown to activate signaling pathways, produce oxidative stress, stimulate hormone secretion and induce both apoptotic and necrotic death. We hypothesize that studying the genetic response of primary human dermal fibroblasts exposed to nsEP, will gain insight into the molecular mechanism(s) either activated directly by nsEP, or indirectly through electrophysiology interactions. MethodsMicroarray analysis in conjunction with quantitative real time polymerase chain reaction (qRT-PCR) was used to screen and validate genes selectively upregulated in response to nsEP exposure. ResultsExpression profiles of 486 genes were found to be significantly changed by nsEP exposure. 50% of the top 20 responding genes coded for proteins located in two distinct cellular locations, the plasma membrane and the nucleus. Further analysis of five of the top 20 upregulated genes indicated that the HDFa cells’ response to nsEP exposure included many elements of a mechanical stress response. ConclusionsWe found that several genes, some of which are mechanosensitive, were selectively upregulated due to nsEP exposure. This genetic response appears to be a primary response to the stimuli and not a secondary response to cellular swelling. General significanceThis work provides strong evidence that cells exposed to nsEP interpret the insult as a mechanical stress.

A demultiplexing unit for separating incident and reflected nano- and picosecond pulse signals

A device on the basis of a double directional bridge for separating ultrawideband pulse signals that are incident on and reflected from an arbitrary load is described. The experimental results from studies of the device using picosecond (40 ps) and nanosecond (10 ns) electrical pulses are presented. A test pulse that feeds the input port comes to a device under test (DUT) with an attenuation of 5 dB. The device separates the resulting incident and reflected pulses that arrive at different ports. The isolation between the ports of the incident and reflected pulses is at least 20 dB in the operating-frequency range from 300 kHz to 16 GHz.

Fast damaging processes in the TaN thin film absorbers under action of nanosecond electrical pulses

Purpose The purpose of this paper is to investigate damaging processes in TaN thin film absorbers under action of high-voltage electrical pulse of nanosecond duration. Despite having mechanical origin of crack opening, estimation based on the readings from oscillograms shows uncharacteristically high velocities of the crack propagation. Design/methodology/approach Microscopic images of damaged absorbers showing the final result of the damaging process provided initial information about its geometrical peculiarities. Then, to clarify the dynamics of the process, the authors create the model of the crack, having elements of self-similarities and multiple stage opening. The influence of heating induced by current concentration at crack tip and of magnetic stress of this concentrated current are both included in the model. Findings Using physical parameters of TaN layers with flowing current and performing calculations the authors define the conditions required to initiate the damaging process and to sustain it. Danger of such damage is relevant for high-Tc superconducting thin films after their switching to normal state which is induced by the high-voltage pulse. Practical implications There were made recommendations to manufactures aiming to improve electrical durability of the absorbers in an effort to prevent the damaging influence of power nanosecond electrical pulses. Originality/value Three stage opening model implies the appearance of zone of high-energy dissipation that can lead to detonation-like destruction of the film and, therefore, explain the high velocities of crack propagation.

Effect of electromagnetic radiation on an array of noninteracting carbon nanoribbons in the presence of nanosecond electrical pulses

For zigzag carbon nanoribbons (m-ZGNR), the dependence of the nonlinear current on the intensity of terahertz radiation with an inclined leading-edge width ΔT = 10−10 s under a dc electric field is studied for odd m. It is theoretically and numerically shown that the nonlinear surface current can be two orders higher in comparison with ordinary carbon nanotubes. A strong dependence of the current on the ribbon width is established.

Assessment of cytoplasm conductivity by nanosecond pulsed electric fields.

The aim of this paper is to propose a new method for the better assessment of cytoplasm conductivity, which is critical to the development of electroporation protocols as well as insight into fundamental mechanisms underlying electroporation. For this goal, we propose to use nanosecond electrical pulses to bypass the complication of membrane polarization and a single cell to avoid the complication of the application of the "mixing formulas." Further, by suspending the cell in a low-conductivity medium, it is possible to force most of the sensing current through the cytoplasm for a more direct assessment of its conductivity. For proof of principle, the proposed technique was successfully demonstrated on a Jurkat cell by comparing the measured and modeled currents. The cytoplasm conductivity was best assessed at 0.32 S/m and it is in line with the literature. The cytoplasm conductivity plays a key role in the understanding of the basis mechanism of the electroporation phenomenon, and in particular, a large error in the cytoplasm conductivity determination could result in a correspondingly large error in predicting electroporation. Methods for a good estimation of such parameter become fundamental.

Permeabilization of yeast Saccharomyces cerevisiae cell walls using nanosecond high power electrical pulses

The electrical field-induced changes of the yeast Saccharomyces cerevisiae cells permeabilization to tetraphenylphosphonium (TPP+) ions were studied using square-shaped, nanosecond duration high power electrical pulses. It was obtained that pulses having durations ranging from 10 ns to 60 ns, and generating electric field strengths up to 190 kV/cm significantly (up to 65 times) increase the absorption rate of TPP+ ions without any detectible influence on the yeast cell viability. The modelling of the TPP+ absorption process using a second order rate equation demonstrates that depending on the duration of the pulses, yeast cell clusters of different sizes are homogeniously permeabilized. It was concluded, that nanosecond pulse-induced permeabilization can be applied to increase the operational speed of whole cell biosensors.