Pulsed Plasma Jet Research Articles

Carbon-based flexible micro-supercapacitor fabrication via mask-free ambient micro-plasma-jet etching

We demonstrate a general and facile method to fabricate all-solid-state flexible micro-supercapacitors (MSCs) with micropatterned multi-walled carbon nanotube (MWNT) electrodes via mask-free micro-plasma-jet etching in ambient conditions. Localized pulsed plasma jet etches the MWNTs rapidly and produces the interdigitated electrode patterns by scanning. This mask-free patterning technique is easy operated, cost-effective, readily scalable, free from photoresist contamination and applicable to various kinds of carbon-based materials. A solid-state polyvinyl alcohol-H3PO4 gel electrolyte is introduced to realize an all-solid-state flexible MSC assembly. Cyclic voltammetry measurements exhibit the expected electrical double layer behavior. The fabricated MSC with twelve interdigitated electrodes exhibits a stack capacitance of 2.02 F cm−3 at a scan rate of 10 mV s−1. Moreover, the MSC shows stable performance under repeated bending, with retention of 98.2% of capacitance after 600 bending cycles. Furthermore, both the output voltage and the total capacitance of the MSC could be controlled via the serial or parallel connection.

Small unilamellar liposomes as a membrane model for cell inactivation by cold atmospheric plasma treatment

Cold atmospheric plasma is thought to be a promising tool for numerous biomedical applications due to its ability to generate a large diversity of reactive species in a controlled way. In some cases, it can also generate pulsed electric fields at the zone of treatment, which can induce processes such as electroporation in cell membranes. However, the interaction of these reactive species and the pulse electric field with cells in a physiological medium is very complex, and we still need a better understanding in order to be useful for future applications. A way to reach this goal is to work with model cell membranes such as liposomes, with the simplest physiological liquid and in a controlled atmosphere in order to limit the number of parallel reactions and processes. In this paper, where this approach has been chosen, 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) small unilamellar vesicles (SUV) have been synthesized in a phosphate buffered aqueous solution, and this solution has been treated by a nanosecond pulsed plasma jet under a pure nitrogen atmosphere. It is only the composition of the plasma gas that has been changed in order to generate different cocktails of reactive species. After the quantification of the main plasma reactive species in the phosphate buffered saline (PBS) solution, structural, surface charge state, and chemical modifications generated on the plasma treated liposomes, due to the interaction with the plasma reactive species, have been carefully characterized. These results allow us to further understand the effect of plasma reactive species on model cell membranes in physiological liquids. The permeation through the liposomal membrane and the reaction of plasma reactive species with molecules encapsulated inside the liposomes have also been evaluated. New processes of degradation are finally presented and discussed, which come from the specific conditions of plasma treatment under the pure nitrogen atmosphere.

Space-time resolved density of helium metastable atoms in a nanosecond pulsed plasma jet: influence of high voltage and pulse frequency

Using tunable diode laser absorption spectroscopy, the spatio-temporal distributions of the helium He(23S1) metastable atoms’ density were measured in a plasma jet propagating in ambient air. The plasma jet was produced by applying short duration high voltage pulses on the electrodes of a DBD-like structure, at a repetition rate in the range 1–30 kHz. In addition to the metastable density, the spatial distribution of helium 587 nm emission intensity was also investigated to give insight into the excitation mechanisms of the He(33D) excited state inside the dielectric tube, in which no laser measurement can be performed. It is demonstrated that the shape of the radial distribution of helium He(23S1) metastable atoms strongly depends on the polarity of the applied voltage and on the repetition frequency. For positive applied voltages, a dramatic constriction of the excited species production is observed whenever the pulse repetition frequency is higher than 6 kHz, and the voltage higher than 5 kV. This shrinking of the jet structure induces an increase by one order of magnitude of the metastable atoms’ density in the jet centre which reaches values as high as 1014 cm−3. Beyond a critical distance, associated to a transition between a positive streamer and a negative one, the distribution of the excited atoms gets back to an annular structure. For the negative polarity, no shrinking effect correlated to the pulse repetition frequency was observed. The on-axis constriction of the excited species for the high repetition rate and positive polarity is attributed to a memory effect induced by the negative ions, having a lifetime of hundreds of microseconds, left between successive pulses at the periphery of the helium gas flow.

The Comparative Study of the Structure and Phase Composition of Ni-Based Coatings Modified by Plasma Jet or Electron Beam

The paper deals with the results of the comparative study into the structure and phase composition, as well as some properties (microhardness, corrosion resistance) of Ni-based powder coatings before and after their modification by DC electron beam or DC pulse plasma jet, according to the modes recommended on the basis of model calculations of the temperature profiles at irradiation. The transmission electron microscopy and Xray analysis have revealed that irradiation leads to an increase in the volume fraction of reinforcing nanosized intermetallic components in the coatings. There were established certain similarities and differences in the structure and properties of the coatings modified by different types of irradiation. The microhardness of the irradiated coatings has increased in both cases along with the growth of the volume fraction of the CrNi3 particle phase. However, it was found that the diffusion zone in the coatings modified by plasma jet is higher than that of the coatings modified by electron irradiation. The coating surface melted by the electron beam has a marked reduction of its roughness and better homogenization of the microstructure therefore demonstrating better adhesion and corrosion resistance.

Exploring the polymerization of bioactive nano-cones on the inner surface of an organic tube by an atmospheric pressure pulsed micro-plasma jet

In this paper, the successful deposition of acrylic acid polymer (PAA) nano-cones on the inner surface of a polyvinyl chloride (PVC) tube using an atmospheric pressure pulsed plasma jet (APPJ) with acrylic acid (AA) monomer is presented. Optical emission spectroscopy (OES) measurements indicated that various reactive radicals, such as OH and O, existed in the plasma jet. Moreover, the pulsed current proportionally increased with the increase in the applied voltage. The strengthened stretching vibration of the carbonyl group (CO) at 1700cm−1, shown in the ATR-FTIR spectra, clearly indicated that the PAA was deposited on the PVC surface. The maximum height of the PAA nano-cones deposited by this method ranged from 150 to 200nm. FTIR and XPS results confirmed the enhanced exposure of the carboxyl groups on the modified PVC surface, which was considered highly beneficial for successfully immobilizing a high density of biomolecules. The XPS data showed that the carbon ratios of the COH/R and COOH/R groups increased from 7.03% and 2.6% to 18.69% and 6.81%, respectively (more than doubled) when an Ar/O2 plasma with AA monomer was applied to treat the inner surface of the PVC tube. Moreover, the enhanced attachment density of MC3T3-E1 bone cells was observed on the PVC inner surface coated with PAA nano-cones.

Microwave antenna based on a pulsed plasma jet

The results of experimental studies of a microwave antenna based on plasma jet created by a pulsed discharge in a capillary with an ablative wall are presented. It is shown that the electromagnetic parameters of the plasma jet are close to metal, which enables its efficient operation in the mode of an asymmetric quarterwave dipole for transmitting and receiving electromagnetic waves in the centimeter–decimeter range. The influence of the discharge parameters, the flow regimes of the plasma jet (subsonic and supersonic), and various impact factors (high-speed gas flow, a source of low-temperature plasma with ne ~ 1012 cm–3, etc.) on the receiving and transmitting operating modes have been studied. The possibility of using a plasma jet for radio communication of hypersonic flying vehicles and related problems is discussed.

Plasma effects on the generation of reactive oxygen and nitrogen species in cancer cells in-vitro exposed by atmospheric pressure pulsed plasma jets

Atmospheric pressure pulsed helium plasma jets are utilized for plasma-cell interactions. The effect of operating parameters such as applied voltage, pulse repetition frequency, and duty ratio on the generation of specific reactive oxygen and nitrogen species in gas and liquid phases and within cells is investigated. The apoptotic changes detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling assay in cells caused by plasma exposure are observed to correlate well with the levels of extracellular and intracellular reactive oxygen and nitrogen species.

Atmospheric-Pressure Plasma Polymerization of Acrylic Acid: Gas-Phase Ion Chemistry

To improve understanding of atmospheric-pressure plasma polymerization processes, the gas-phase ion chemistry of acrylic acid produced in a microsecond pulsed atmospheric pressure plasma jet has been studied using ambient mass spectrometry. Acrylic acid monomer was introduced into the helium feed prior to entry into the active discharge region and the pulse duty cycle was varied from 10–90% for frequencies of 5 and 10 kHz. The ionic mass spectra show a rich variety of species up to 450 Da with prominent peaks at masses corresponding to both positive and negative oligomer ions, [nM+H]+ and [nM-H]−, with up to n = 6 for positive ions and n = 4 for negative ions. Through variation of the pulse voltage parameters, the mass distribution of the oligomer ions produced in the outflow can be manipulated.

Formation of reactive oxygen and nitrogen species by repetitive negatively pulsed helium atmospheric pressure plasma jets propagating into humid air

Atmospheric pressure plasma jets have many beneficial effects in their use in surface treatment and, in particular, plasma medicine. One of these benefits is the controlled production of reactive oxygen and nitrogen species (RONS) in the active discharge through the molecular gases added to the primary noble gas in the input mixture, and through the interaction of reactive species in the plasma effluent with the ambient air. In this computational investigation, a parametric study was performed on the production of RONS in a multiply pulsed atmospheric pressure plasma jet sustained in a He/O2 mixture and flowing into ambient humid air. The consequences of flow rate, O2 fraction, voltage, and repetition rate on reactant densities after a single discharge pulse, after 30 pulses, and after the same total elapsed time were investigated. At the end of the first discharge pulse, voltage has the greatest influence on RONS production. However, the systematic trends for production of RONS depend on repetition rate and flow rate in large part due to the residence time of RONS in the plasma zone. Short residence times result in reactive species produced by the previous pulse still being in the discharge tube or in the path of the ionization wave at the next pulse. The RONS therefore accumulate in the tube and in the near effluent on a pulse-to-pulse basis. This accumulation enables species requiring multiple reactions among the primary RONS species to be produced in greater numbers.

MODELING OF HEATING THE METAL SURFACE DURING ELECTROEXPLOSIVE ALLOYING WITH DIFFERENT SHAPE OF THE HEAT PULSE

The simulation of the heating of the surface of metals and alloys during the treatment by multi-phase pulsed plasma jet formed from the products of explosion of electrical conductors is held. The depth of the melting zone was determined for the two pulse shapes – rectangular, and bimodal, which corresponds to the structure of the jet, including rapid plasma front and relatively slow rear containing condensed particles of the explosion products. Comparison of the simulation results showed that the pulse shape has little effect on the depth of the alloying zone.

Experimental demonstration of Martian soil simulant removal from a surface using a pulsed plasma jet.

A plasma jet produced in a small coaxial plasma gun operated at voltages up to 2 kV and working in pure carbon dioxide (CO2) at a few Torr is used to remove Martian soil simulant from a surface. A capacitor with 0.5 mF is charged up from a high voltage source and supplies the power to the coaxial electrodes. The muzzle of the coaxial plasma gun is placed at a few millimeters near the dusty surface and the jet is fired parallel with the surface. Removal of dust is imaged in real time with a high speed camera. Mars regolith simulant JSC-Mars-1A with particle sizes up to 5 mm is used on different types of surfaces made of aluminium, cotton fabric, polyethylene, cardboard, and phenolic.

Pulsed microwave-driven argon plasma jet with distinctive plume patterns resonantly excited by surface plasmon polaritons**Project supported by the National Natural Science Foundation of China (Grant Nos. 11105002 and 61170172), the Natural Science Foundation of Anhui Province, China (Grant Nos. 1408085QA16 and 1408085ME101), the China Postdoctoral Science Foundation (Grant No. 2014M551788), and the Open-end Fund of State Key Laboratory of Advanced

Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air. The plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric tubes. The electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon polaritons. Moreover, for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave, the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas, frequencies of pulsed modulator, duty cycles of pulsed microwave, peak values of input microwave power, and even by using different materials of dielectric tubes. In addition, the emission spectrum, the plume temperature, and other plasma parameters are measured, which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications.

Pulsed laminar arc jet with synchronized suspension injection-spectroscopic studies

The uncontrolled arc plasma instabilities are one of the difficulties encountered in in suspension plasma spraying. The improvement of this process is usually attempted by means of the reduction of arc fluctuations. The following paper presents a new approach to overcome these arc instabilities. The principle is to produce a pulsed laminar plasma jet combined with phased injection of liquid droplets. This is achieved by the particular design of the plasma torch which allows coupling two modes of the plasma oscillations, restrike and Helmholtz. The plasma produced in a new mode is laminar and pulsed, characterized by a modulated enthalpy, what permits to make the synchronization with the suspension injection. The droplets are injected using a piezoelectric device, based on drop-on-demand method, triggered by the voltage signal. The results are evaluated by time-resolved imaging technique and Time- Resolved Optical Emission Spectroscopy.

Self-consistent fluid modeling and simulation on a pulsed microwave atmospheric-pressure argon plasma jet

In present study, a pulsed lower-power microwave-driven atmospheric-pressure argon plasma jet has been introduced with the type of coaxial transmission line resonator. The plasma jet plume is with room air temperature, even can be directly touched by human body without any hot harm. In order to study ionization process of the proposed plasma jet, a self-consistent hybrid fluid model is constructed in which Maxwell's equations are solved numerically by finite-difference time-domain method and a fluid model is used to study the characteristics of argon plasma evolution. With a Guass type input power function, the spatio-temporal distributions of the electron density, the electron temperature, the electric field, and the absorbed power density have been simulated, respectively. The simulation results suggest that the peak values of the electron temperature and the electric field are synchronous with the input pulsed microwave power but the maximum quantities of the electron density and the absorbed power density are lagged to the microwave power excitation. In addition, the pulsed plasma jet excited by the local enhanced electric field of surface plasmon polaritons should be the discharge mechanism of the proposed plasma jet.

Control of mean separation in shock boundary layer interaction using pulsed plasma jets

The current study investigates the use of pulsed plasma jets (spark jets) to reduce the separation induced by shock wave-boundary layer interaction generated by a $$20^{\circ }$$ compression ramp in a Mach 3 flow with a Reynolds number of 5,400, based on the undisturbed boundary layer momentum thickness. Surface oil streak visualization is used in a parametric study to determine the optimum pulsing frequency of the jet, the optimum distance of the jet from the compression corner, and the optimum configuration of the jets. Several 3-jet actuator configurations are tested, including those where the jets are pitched, and pitched and skewed. The jet pulsing frequency is varied between 2 and 4 kHz, corresponding to a Strouhal number based on separation length of 0.012 and 0.023. Particle image velocimetry is used to characterize the effect that the actuators have on the reattached boundary layer profile on the ramp surface. Results show that plasma jets pitched at $$20^{\circ }$$ from the wall, and pulsed at a Strouhal number of 0.018, can reduce the distance between the separation line and the compression ramp corner by up to 40 % and increase the integrated momentum in the downstream reattached boundary layer, albeit with a concomitant increase in the shape factor.

The production mechanisms of OH radicals in a pulsed direct current plasma jet

The production mechanism of OH radicals in a pulsed DC plasma jet is studied by a two-dimensional (2-D) plasma jet model and a one-dimensional (1-D) discharge model. For the plasma jet in the open air, electron-impact dissociation of H2O, electron neutralization of H2O+, as well as dissociation of H2O by O(1D) are found to be the main reactions to generate the OH species. The contribution of the dissociation of H2O by electron is more than the others. The additions of N2, O2, air, and H2O into the working gas increase the OH density outside the tube slightly, which is attributed to more electrons produced by Penning ionization. On the other hand, the additions of O2 and H2O into the working gas increase the OH density inside the tube substantially, which is attributed to the increased O (1D) and H2O concentration, respectively. The gas flow will transport high density OH out of the tube during pulse off period. It is also shown that the plasma chemistry and reactivity can be effectively controlled by the pulse numbers. These results are supported by the laser induced fluorescence measurements and are relevant to several applications of atmospheric-pressure plasmas in health care, medicine, and materials processing.

The Titan Haze Simulation experiment on COSmIC: Probing Titan’s atmospheric chemistry at low temperature

The aim of the Titan Haze Simulation (THS) experiment is to contribute to a better understanding of aerosol formation in Titan’s atmosphere through the study of the chemical formation pathways that link the simpler gas phase molecules resulting from the first steps of the N2–CH4 chemistry, to the more complex gas phase precursors of aerosols; and more specifically, to investigate the role of polycyclic aromatic hydrocarbons (PAHs) and nitrogenated polycyclic aromatic hydrocarbons (PANHs), among other hydrocarbons, in this process. In the THS experiment developed at the NASA Ames Cosmic simulation facility (COSmIC), Titan’s atmospheric chemistry is simulated by a pulsed plasma jet expansion at temperature conditions (∼150K) close to those found in Titan’s atmosphere in regions where aerosols are formed. In addition, because of the very short residence time of the gas in the plasma discharge, only the initial steps of the chemistry occur, making the COSmIC/THS a unique tool to study the first and intermediate (when adding heavier precursors to the initial N2–CH4 mixture) steps of Titan’s atmospheric chemistry at low temperature as shown in the study presented here. We further illustrate the potential of COSmIC/THS for the simulation of Titan’s atmospheric chemistry by presenting very promising results from a preliminary comparison of the laboratory data to data from the Cassini Plasma Spectrometer–Ion Beam Spectrometer (CAPS–IBS) instrument.

Degradation of tungsten under the action of a plasma jet

The degradation of the surface and structure of single-crystal tungsten and sintered powder tungsten during the action of a pulsed plasma jet is studied. It is shown that the degradation of a tungsten target during the action of a plasma jet with an energy flux density of 0.25–1 MJ/m2 is accompanied by surface evaporation and melting and the fracture of surface layers on scales of 150–250 μm. The results of a numerical simulation of the thermomechanical processes that occur in a tungsten target during the action of a plasma jet are presented. The degradation of tungsten during the action of a plasma jet is shown to proceed almost continuously from the action (evaporation, melting) to the times that are more than three orders of magnitude longer than the action time, which is caused by the thermomechanical processes occurring in the tungsten target. Moreover, the action of thermal stresses leads to structural and morphological changes throughout the sample volume, and these changes are accompanied by recrystallization in adiabatic shear bands.

Manufacture of Model Apollo Capsule Utilizing Pulsed-Plasma Jet for Bow Shock Dispersion

High speed Schlieren imaging, pressure tapping points and optical emission spectroscopy for temperature and heat flux data are essential measurement techniques for analysis of bow shock dispersion, aerodynamic performance or heat transfer of spacecraft in atmospheric re-entry. However, design and manufacturing of a high voltage pulsed-plasma jet for testing in a supersonic counterflow deserves careful examination. High voltage electrification combined with high temperature sparking between electrodes possesses several design difficulties and manufacturing challenges which need to be addressed that form the basis of the design principals and manufacturing methodology of an Apollo capsule pulsed-plasma jet for successful testing and experimentation of the model.

Synchronization of Suspension Plasma Spray Injection with the Arc Fluctuations

Poorly controlled heat and momentum transfers between plasma and material, plasma instabilities are some of the difficulties encountered in suspension plasma spraying. The improvement of this method is usually attempted by means of the reduction of arc fluctuations. This paper presents a new approach to the injection of reactive material in an arc jet. The principle is to produce a pulsed laminar plasma jet combined with phased injection of liquid droplets. This is achieved by the particular design of the plasma torch that works at moderate power and following a resonant mode. The droplets are injected using a piezoelectric device, based on drop-on-demand method, triggered by the voltage signal sampled at the torch connections. The results are evaluated by time-resolved imaging technique that shows how the trajectories are influenced by the moment at which the droplets penetrate the plasma jet.