Gas Jet Plasma Research Articles

Modeling Gas Plasma-Tissue Interactions in 3D Collagen-Based Hydrogel Cancer Cell Cultures

Gas plasma jet technology was recently identified as a potential adjuvant in the fight against cancer. Here, the partial ionization of gas yields the local formation of an exceptional variety of highly reactive oxygen (ROS) and nitrogen (RNS) species, which are considered the main actors of plasma-induced antitumor effects. Yet, fundamental knowledge in preclinical plasma research relies on the predominant use of two-dimensional cell culture systems, despite causing significant shifts in redox chemistries that largely limit translational relevance. So far, the intricacy of studying complex plasma-tissue interactions causes substantial knowledge gaps concerning the key mechanisms and therapeutical limitations of plasma treatment in a living organism. Identifying physiologically relevant yet simplified tissue models is vital to address such questions. In our study, a side-by-side comparison of conventional and pre-established hydrogel models emphasized this discrepancy, revealing a marked difference in plasma-induced toxicity related to species distribution dynamics. Chemically embedded, fluorescent reporters were further used to characterize reactive species' fingerprints in hydrogels compared to liquids. In addition, a thirteen cell-line screening outlined the widespread applicability of the approach while indicating the need to optimize growth conditions dependent on the cell line investigated. Overall, our study presents important implications for the implementation of clinically relevant tissue culture models in preclinical plasma medicine in the future.

Gas Flow Shaping via Novel Modular Nozzle System (MoNoS) Augments kINPen-Mediated Toxicity and Immunogenicity in Tumor Organoids.

Medical gas plasma is an experimental technology for anticancer therapy. Here, partial gas ionization yielded reactive oxygen and nitrogen species, placing the technique at the heart of applied redox biomedicine. Especially with the gas plasma jet kINPen, anti-tumor efficacy was demonstrated. This study aimed to examine the potential of using passive flow shaping to enhance the medical benefits of atmospheric plasma jets (APPJ). We used an in-house developed, proprietary Modular Nozzle System (MoNoS; patent-pending) to modify the flow properties of a kINPen. MoNoS increased the nominal plasma jet-derived reactive species deposition area and stabilized the air-plasma ratio within the active plasma zone while shielding it from external flow disturbances or gas impurities. At modest flow rates, dynamic pressure reduction (DPR) adapters did not augment reactive species deposition in liquids or tumor cell killing. However, MoNoS operated at kINPen standard argon fluxes significantly improved cancer organoid growth reduction and increased tumor immunogenicity, as seen by elevated calreticulin and heat-shock protein expression, along with a significantly spurred cytokine secretion profile. Moreover, the safe application of MoNoS gas plasma jet adapters was confirmed by their similar-to-superior safety profiles assessed in the hen's egg chorioallantoic membrane (HET-CAM) coagulation and scar formation irritation assay.

Study on energy extraction in the process of combustion plasma plume deflection controlled by MHD

This paper presents a new method of extracting electric energy in the process of realizing thrust vector by magnetron gas plasma. Based on the model scramjet, the combustion plasma scheme is adopted, during the experiment, Cs2CO3 was put into a high-temperature environment to excite its own properties, so as to obtain the product Under the action of external magnetic field, it is verified that electric energy can be extracted in the process of plasma jet deflection, and the results are analyzed from the mechanism. Finally, the specific numerical results of magnetic field intensity and outgoing gas temperature are obtained, the average extraction voltage is 600 mV, indicating that ionized seeds enhance the ionization degree of gas. In the process of gas plasma jet of magnetic control scramjet, the scheme of extracting energy is feasible.

(Invited) On Several Atmospheric Pressure Plasma Sources

In this talk, firstly, several plasma jets developed in our group are presented, including a nobble gas plasma jet for root canal treatment and four air plasma jet devices [1, 2] . Secondly, several interesting physics phenomena of plasma jets are introduced, such as the repeatability of the plasma bullet, the plasma interruption behavior, the plasma transfer dielectric phenomenon, and the appearance of multiple plasma bullet per voltage pulse [2-4] . Thirdly, the state-of-the-art on the measurement of VUV emission of atmospheric pressure air plasma is discussed and our results by using differential pumping system as EUV window are presented [5] . Fourthly , several different configurations of nonequal gap distance DBD are described [6, 7] . Finally, an atmospheric pressure glow discharge in air stabilized by a magnetic field and its application on nitrogen fixation are rep orted. Li, J. Liu, X. Lu, A large atmospheric pressure nonequilibrium open space air plasma based on a rotating electrode,P lasma Sources Sci. Technol. 29, 045015 (2020)Lu*, G. Naidis, M. Laroussi, K. Ostrikov, Guided ionization waves: Theory and experiments. Physics Reports , 540,123-166 (2014)Lu*, and Kostya (Ken) Ostrikov, Guided ionization waves: The physics of repeatability, Appl. Phys, Rev ,5, 031102 (2018)Liu, L. Nie, Y. Xian, X. Lu*, The twisted behavior of a rotating electrode atmospheric-pressure argon plasma jet, J. Phys. D: Appl. Phys. 54, 185201 (2021)F Liu, L Nie, X Lu, J Stephens and K Ostrikov, Atmospheric plasma VUV photon emission, Plasma Sources Sci. Technol. 29, 065001(2020)Li, S. Jin, Y. Xian, L. Nie, D. Liu, X. Lu*, A non-equal gap distance dielectric barrier discharge: between a wedge-shaped and a plane-shaped electrode, Plasma Sources Sci. Technol. 30, 065026 (2021)Jin, Z. Li, Y. Xian, L. Nie, X. Lu*, A non‐equal gap distance dielectric barrier discharge: Between cone‐shape and cylinder‐shape electrodes, High Voltage , 1-9 (2021)

A Highly Efficient Microwave Plasma Jet Based on Evanescent-Mode Cavity Resonator Technology

This article introduces a novel low-power and highly efficient atmospheric pressure microwave plasma jet (APPJ). Specifically, a capillary tube passing through the critical gap area of a high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> evanescent-mode (EVA) cavity resonator provides a controlled gas flow rate to realize microwave gas breakdown and plasma jet formation even with milliwatts range input power. The theory, simulation, fabrication, and characterization of the introduced plasma jet technology are discussed. A prototype 2.45 GHz device can operate at powers as low as 400 mW with >80% power efficiency and provides up to a 6-mm-long plasma jet with electron density in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{15}$ </tex-math></inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-3}$ </tex-math></inline-formula> in a 1 to 7 slpm helium flow rate. Considering its high plasma density as well as low operating power and jet temperature, this device is a viable and safe solution for a wide range of applications, including emerging plasma medicine needs.

Numerical analysis of deflection control of a gas plasma jet based on magnetohydrodynamic staggered electrode configuration

To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic (MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.

Conductivity augments ROS and RNS delivery and tumor toxicity of an argon plasma jet

Gas plasma jet technology was recently identified as a potential adjuvant in the palliation of cancer patients. However, a practical point raised is if higher therapeutic efficacy is achieved with the gas plasma applied in direct contact to the tumor tissue (conducting) or during treatment with the remote cloud of reactive oxygen and nitrogen species (ROS/RNS) being expelled. In a bedside-to-bench study, this clinical question was translated into studying these two distinct treatment modalities using a three-dimensional tumor cell-matrix-hydrogel assay with subsequent quantitative confocal imaging. Z-resolved fluorescence analysis of two cancer cell lines revealed greater toxicity of the conducting mode. This result was re-iterated in the growth analysis of vascularized tumor tissue cultured on chicken embryos' CAM using in ovo bioluminescence imaging. Furthermore, for conducting compared to free mode, optical emission spectroscopy revealed stronger RNS signal lines in the gas phase, while both ROS/RNS deposition in the liquid was drastically exacerbated in the conducting mode. Altogether, our results are vital in understanding the importance of standardized treatment distances on the therapeutic efficacy of gas plasma exposure in clinical oncology and will help to give critical implications for clinicians involved in plasma onco-therapy in the future.

Development of Decontamination Treatment Techniques for Dry Powder Foods by Atmospheric-Pressure Nonequilibrium DC Pulse Discharge Plasma Jet

Dry powder food ingredients imported to Japan contain large amounts of viable bacteria and coliform bacteria, and we need a simple, low-cost, dry nonthermal decontamination method without spoiling nutrients, color, fragrance, and flavor. In this study, it is shown that the decontamination performance against viable bacteria and coliform bacteria is proportional to the plasma irradiation time when OH and O3 radicals are incident on the dry powder food ingredients placed in an atmospheric-pressure nonequilibrium DC pulse discharge Ar + O2 mixture gas plasma jet. Our study revealed that there is a correlation between the plasma irradiation time and DC pulse frequency increase and the decontamination effect on the general bacterial count.

Cross-Beam Energy Transfer Saturation by Ion Heating.

We measure cross-beam energy transfer (CBET) saturation by ion heating in a gas-jet plasma characterized using Thomson scattering. A wavelength-tunable ultraviolet (UV) probe laser beam interacts with four intense UV pump beams to drive large-amplitude ion-acoustic waves. For the highest-intensity interactions, the power transfer to the probe laser drops, demonstrating ion-acoustic wave saturation. Over this time, the ion temperature is measured to increase by a factor of 7 during the 500-ps interaction. Particle-in-cell simulations show ion trapping and a subsequent ion heating consistent with measurements. Linear kinetic CBET models are found to agree well with the observed energy transfer when the measured plasma conditions are used.

Medical gas plasma promotes blood coagulation via platelet activation

Major blood loss still is a risk factor during surgery. Electrocauterization often is used for necrotizing the tissue and thereby halts bleeding (hemostasis). However, the carbonized tissue is prone to falling off, putting patients at risk of severe side effects, such as dangerous internal bleeding many hours after surgery. We have developed a medical gas plasma jet technology as an alternative to electrocauterization and investigated its hemostatic (blood clotting) effects and mechanisms of action using whole human blood. The gas plasma efficiently coagulated anticoagulated donor blood, which resulted from the local lysis of red blood cells (hemolysis). Image cytometry further showed enhanced platelet aggregation. Gas plasmas release reactive oxygen species (ROS), but neither scavenging of long-lived ROS nor addition of chemically-generated ROS were able to abrogate or recapitulate the gas plasma effect, respectively. However, platelet activation was markedly impaired in platelet-rich plasma when compared to gas plasma-treated whole blood that moreover contained significant amounts of hemoglobin indicative of red blood cell lysis (hemolysis). Finally, incubation of whole blood with concentration-matched hemolysates phenocopied the gas plasmas-mediated platelet activation. These results will spur the translation of plasma systems for hemolysis into clinical practice.

Optical Investigations of N2 Atmospheric Pressure Plasma Jets

In this study, firstly, N 2 atmospheric pressure plasma jet (APPJ) system was presented. Nitrogen gas discharges are produced as jet using an AC power supply which can be adjusted between 6-18 kV and the frequency value of 13-20 kHz at atmospheric pressure. The change of length of produced atmospheric pressure nitrogen plasma jet, according to gas flow rate has been investigated and the produced jet length was approximately 2 cm for 5 L/min when the applied voltage was 18 kV and the frequency was 15 kHz. Nitrogen plasma jet produced at atmospheric pressure was examined with optical emission spectroscopy (OES) and the correlation between gas flow rate and emission spectra were investigated. Furthermore, electron temperature and electron density of atmospheric pressure nitrogen gas plasma jet were estimated under different flow rates of N 2 gas.

(Invited) Electrochemical Characterization of the Interface between Atmospheric Noble Gas Plasma Jet and Aqueous Solution

Elucidation of general features of the interface between atmospheric pressure plasma jets and aqueous solutions would be beneficial to environmental, agricultural and biomedical applications. Such fundamental descriptions are critically important to design process chemistries and scale-up production. In this presentation, our recent efforts towards that end will be discussed. The focus of the talk will be on free jets of low temperature radiofrequency (RF) plasma generated using noble gas in contact with water, in contrast to the often used two-electrode configuration with e.g. micro-plasmas. Experiments will be presented in support of a perspective that views the plasma-liquid interface as a boundary condition that locally constrains the reduction potential, which can be controlled using parameters such as the plasma gas composition, applied RF power, and jet stand-off distance. A unique spatial distribution of the reduction potential that develops to maintain charge neutrality in the aqueous solution will be presented. The consequences for process design and scale-up will be expanded upon.

Medical Gas Plasma Jet Technology Targets Murine Melanoma in an Immunogenic Fashion.

Medical technologies from physics are imperative in the diagnosis and therapy of many types of diseases. In 2013, a novel cold physical plasma treatment concept was accredited for clinical therapy. This gas plasma jet technology generates large amounts of different reactive oxygen and nitrogen species (ROS). Using a melanoma model, gas plasma technology is tested as a novel anticancer agent. Plasma technology derived ROS diminish tumor growth in vitro and in vivo. Varying the feed gas mixture modifies the composition of ROS. Conditions rich in atomic oxygen correlate with killing activity and elevate intratumoral immune‐infiltrates of CD8+ cytotoxic T‐cells and dendritic cells. T‐cells from secondary lymphoid organs of these mice stimulated with B16 melanoma cells ex vivo show higher activation levels as well. This correlates with immunogenic cancer cell death and higher calreticulin and heat‐shock protein 90 expressions induced by gas plasma treatment in melanoma cells. To test the immunogenicity of gas plasma treated melanoma cells, 50% of mice vaccinated with these cells are protected from tumor growth compared to 1/6 and 5/6 mice negative control (mitomycin C) and positive control (mitoxantrone), respectively. Gas plasma jet technology is concluded to provide immunoprotection against malignant melanoma both in vitro and in vivo.

Experimental study on plasma jet deflection and energy extraction with MHD control

This paper presents an integrated research scheme for vector deflection and energy extraction in a gas plasma jet under Magneto-Hydrodynamic (MHD) control. A MHD-controlled thrust-vector test rig was used to conduct the experimental research. A gas plasma was obtained by injecting ionization seeds of Cs2CO3 into the combustion chamber via artificially forced ionization. The effects of the gas temperature and ionization seed mass fraction on the plasma jet deflection and energy extraction were experimentally verified under an applied magnetic field. The experimental results were analyzed theoretically. The results showed that the deflection amplitude of the gas plasma jet and the extracted voltage signal intensity increased with increasing gas temperature and the ionization seed mass fraction. The extracted dynamic voltage signals proved that the ionization seeds of Cs2CO3 induced gas ionization at 1173 K. The experiment verified that it is feasible to simultaneously achieve jet deflection and extract energy under the action of an external magnetic field.

Experimental investigation on the effect of ionization seed mass fraction on gas plasma jet deflection

In order to study the effect of ionization seed mass fraction on gas plasma jet deflection, Cs2CO3 was selected as ionization seed, and the combustion temperature and conductivity in chemical equilibrium were calculated by Chemkin software. A calculation scheme for mixed combustion of methane with air and Cs2CO3 at initial temperature T0 = 300 K and initial pressure p0 = 1.04 × 105 Pa is determined. The gas temperature and conductivity were calculated when the mass fraction of ionization seed was 1%, 5% and 10%, respectively. According to the calculation results, the quantitative relationship between conductivity and temperature was fitted. The results showed that the fifth-order polynomial had good fitting accuracy for three different seed mass fraction schemes, and high conductivity could be obtained by keeping the excess air coefficient near 0.9. The plasma jet deflection experiments under different working conditions were carried out on a thrust-vector test rig controlled by MHD. The effect of jet deflection is analyzed. The results showed that at the same temperature, the higher the mass fraction of ionization seed is, the higher the conductivity is, the greater the Lorentz force on the plasma is, and the larger the jet deflection angle is. The calculation results can provide theoretical basis for the corresponding experimental research.

Acceleration of electrons in the interaction of a subterawatt laser pulse with a nonuniform plasma

We consider the effect of nonlinear self-focusing and self-modulation processes on the acceleration of electrons in the interaction of a subterawatt femtosecond laser pulse with a gas jet plasma. A three-dimensional particle-in-cell (3D PIC) simulation of the interaction of laser radiation with a low-density nonuniform plasma shows that laser pulse self-focusing that arises when the critical power of relativistic self-focusing determined by the local concentration of plasma electrons exceeds the pulse power results in efficient generation of a plasma wave. Due to a decrease in the phase velocity of the wake plasma wave generated via self-modulation of the laser pulse, electrons are trapped into the accelerating phase of the plasma wave and are accelerated to energies of ∼10 MeV. It is demonstrated that under the conditions for limiting the electrons’ acceleration region by the length of their dephasing, quasi-monoenergetic electron bunches with a characteristic energy of ∼9 MeV can be produced. The effective temperature of the accelerated electrons and their angular distribution, obtained by 3D PIC simulation, are in good agreement with those determined in the experiment.

Electrical, thermal and optical characteristics of plasma torch

Non thermal argon plasma needle at atmospheric pressure was constructed. The experimental set up was based on simple and low cost electric components that generate electrical field sufficiently high at the electrodes to ionize various gases which flow at atmospheric pressure. A high AC power supply was used with 9.6kV peak to peak and 33kHz frequency. The plasma was generated using two electrodes. The voltage and current discharge waveform were measured. The temperature of Ar gas plasma jet at different gas flow rate and distances from the plasma electrode was also recorded. It was found that the temperature increased with increasing frequency to reach the maximum value at 15 kHz, and that the current leading the voltage, which demonstrates the capacitive character of the discharge. The electron temperature was measured at about 0.61 eV, and we calculated the electron number density to be 4.38×1015 cm-3.

Betatron resonance electron acceleration and generation of relativistic electron beams using 200 fs Ti:sapphire laser pulses

The generation of relativistic electron beams with quasi-thermal energy distribution (maximum energy: 30 MeV) by the interaction of a Ti:sapphire laser pulse of 200 fs duration, focussed to an intensity of ∼2.1 × 1018 W cm−2, with an underdense (electron density ∼3.6 × 1019 to ∼1.1 × 1020 cm−3) He gas-jet plasma was observed. We observed two stages of self-focusing of the laser pulse in the plasma. Two groups of accelerated electrons associated with these two stages of laser channeling were also observed, and are attributed to the betatron resonance acceleration mechanism. This is supported by 2D PIC simulations performed using the EPOCH code and a detailed theoretical analysis. Further, the generation of quasi-monoenergetic (ΔE/E ∼ 10%–20%) electron beams with a peak energy of ∼17–22 MeV was also observed, even with such long laser pulses, although with a low probability of occurrence.

Silicon etching of difluoromethane atmospheric pressure plasma jet combined with its spectroscopic analysis

A capacitivly coupled radio-frequency double-pipe atmospheric-pressure plasma jet is used for etching. An argon carrier gas is supplied to the plasma discharge jet; and CH2F2 etch gas is inserted into the plasma discharge jet, near the silicon substrate. Silicon etchings rate can be efficiently-controlled by adjusting the feeding etching gas composition and plasma jet operating parameters. The features of silicon etched by the plasma discharge jet are discussed in order to spatially spreading plasma species. Electronic excitation temperature and electron density are detected by increasing plasma power. The etched silicon profile exhibited an anisotropic shape and the etching rate was maximum at the total gas flow rate of 4500 sccm and CH2F2 concentration of 11.1%. An etching rate of 17 µm/min was obtained at a plasma power of 100 W.

Atmospheric pressure plasma jet treatment of wheat straw for improved compatibility in epoxy composites

ABSTRACTThe aim of this study was to investigate the effects of an atmospheric‐pressure gas plasma jet treatment on the interior and exterior surface characteristics of wheat straw and on the mechanical properties of epoxy composites reinforced with wheat straw. Dry air was used as the process gas in the plasma system. A distance between the nozzle and the substrate surface (DNSS) of 35 mm was determined as the most effective parameter enabling remarkable decreases in the (surface energy) values of both the interior and exterior surfaces of virgin wheat straw. Increased intensities of the peaks related to carbon‐rich species and 11% to 43% decreases in the oxygen/carbon ratios on the surfaces confirmed the more hydrophobic nature of the plasma‐treated wheat straw. A further increase in the DNSS decreased the effectiveness of the plasma treatment, while a decrease in the DNSS caused an inverse effect on the value, probably due to the etching effect of the plasma action, which was supported by the atomic force microscopy analysis. The overall results indicated that the increased hydrophobicity and valley‐like occurrences without sharp pits created by the plasma action improved the compatibility of the wheat straw with the epoxy matrix, which contributed to superior mechanical properties of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45828.