scholarly journals Role of charge accumulation in guided streamer evolution in helium DBD plasma jets

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mikhail Pinchuk ◽  
Anton Nikiforov ◽  
Vadim Snetov ◽  
Zhaoquan Chen ◽  
Christophe Leys ◽  
...  
Keyword(s):  
Duty Cycle ◽  
Strong Field ◽  
Atmospheric Pressure Plasma ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Propagation Mode ◽  
Dbd Plasma ◽  
Duty Cycles ◽  
Ionization Waves

AbstractExperimental data are presented on the evolution of a helium atmospheric pressure plasma jet driven by a tailored voltage waveform generated as bunches of voltage pulses consisting of a superposition of $$\approx 43$$ ≈ 43  kHz bipolar square pulses and $$\approx 300$$ ≈ 300  kHz oscillations. The characteristics of directed ionization waves (guided streamers) are compared for bunches with different first pulse polarities and different bunch duty cycles. The longest and brightest streamers are achieved at the voltage bunch with the first negative pulse and a minimum duty cycle. The dynamics of streamers at the voltage bunch with the first positive pulse are characterized by the shortest length and a lower brightness. The plasma jet length can be smoothly changed by varying the number of pulses in the bunch and the polarity of the first pulse. It is thus possible to precisely localize the region of a strong field in space by combining the parameters of the applied voltage (the duty cycle and polarity of the first pulse of a bunch) with a stepwise propagation mode of a guided streamer.

scholarly journals Study of Modified Area of Polymer Samples Exposed to a He Atmospheric Pressure Plasma Jet Using Different Treatment Conditions

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1028 ◽  
Author(s):  
Thalita M. C. Nishime ◽  
Robert Wagner ◽  
Konstantin G. Kostov
Keyword(s):  
Atmospheric Pressure ◽  
Atmospheric Pressure Plasma ◽  
Plasma Jet ◽  
Industrial Applications ◽  
Plasma Jets ◽  
Limited Area ◽  
Plastic Tube ◽  
Pressure Plasma ◽  
Treatment Conditions ◽  
Jet Modification

In the last decade atmospheric pressure plasma jets (APPJs) have been routinely employed for surface processing of polymers due to their capability of generating very reactive chemistry at near-ambient temperature conditions. Usually, the plasma jet modification effect spans over a limited area (typically a few cm²), therefore, for industrial applications, where treatment of large and irregular surfaces is needed, jet and/or sample manipulations are required. More specifically, for treating hollow objects, like pipes and containers, the plasma jet must be introduced inside of them. In this case, a normal jet incidence to treated surface is difficult if not impossible to maintain. In this paper, a plasma jet produced at the end of a long flexible plastic tube was used to treat polyethylene terephthalate (PET) samples with different incidence angles and using different process parameters. Decreasing the angle formed between the plasma plume and the substrate leads to increase in the modified area as detected by surface wettability analysis. The same trend was confirmed by the distribution of reactive oxygen species (ROS), expanding on starch-iodine-agar plates, where a greater area was covered when the APPJ was tilted. Additionally, UV-VUV irradiation profiles obtained from the plasma jet spreading on the surface confirms such behavior.

Patterns of plasma jet arrays in the gas flow field of non-thermal atmospheric pressure plasma jets

2019 ◽  
Vol 26 (1) ◽  
pp. 013505 ◽  
Author(s):  
M. Hasnain Qaisrani ◽  
Congyun Li ◽  
Pei Xuekai ◽  
M. Khalid ◽  
Xian Yubin ◽  
...  
Keyword(s):  
Flow Field ◽  
Atmospheric Pressure ◽  
Gas Flow ◽  
Atmospheric Pressure Plasma ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Pressure Plasma ◽  
Gas Flow Field

scholarly journals Effects of a Nonthermal Atmospheric Pressure Plasma Jet on Human Gingival Fibroblasts for Biomedical Application

2016 ◽  
Vol 2016 ◽  
pp. 1-9
Author(s):  
Jung-Hwan Lee ◽  
Kyoung-Nam Kim
Keyword(s):  
Cell Death ◽  
Atmospheric Pressure ◽  
Biomedical Application ◽  
Safety Issue ◽  
Atmospheric Pressure Plasma ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Human Gingival Fibroblasts ◽  
Gingival Fibroblasts ◽  
Pressure Plasma

Nonthermal atmospheric pressure plasma jets (APPJ) have been developed and applied in biomedical research as a cancer treatment or bacterial sterilization. However, the drawback of APPJ on normal oral cells during plasma treatment and underlying cell death mechanisms have not been studied and clearly explained, although there is known to be an influence from reactive oxygen species (ROS). Hence, this study investigates whether and how a nonthermal atmospheric pressure air plasma jet kills human normal gingival cells using immortalized human gingival fibroblasts (hTERT-hNOF cells). In this study, a set of physicochemical or biological methods were used to illuminate the killing mechanisms. It was found that ROS were induced intracellularly without a breakdown of the cell wall and apoptosis was involved in cell death when an air APPJ treatment was performed on the cells directly without media; the air treatment only supported a detachment of the cells without increase of ROS. It was also revealed that a correlation between intracellular ROS concentration and cells viability existed. These results indicated that the direct air APPJ treatment possibly raises safety issue to normal tissue and thereby APPJ application in biomedical field needs morein vitroandin vivostudy to optimize it.

scholarly journals Aqueous Gold Nanoparticles Generated by AC and Pulse-Power-Driven Plasma Jet

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1488 ◽  
Author(s):  
Xie ◽  
Qi ◽  
Wang ◽  
Wu ◽  
Li
Keyword(s):  
Color Change ◽  
Coupling Effect ◽  
Local Heating ◽  
Atmospheric Pressure Plasma ◽  
Reaction Dynamics ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Pulse Power ◽  
Reaction Cell ◽  
Neutral Species

In this study, we developed a simple-to-use approach based on an atmospheric pressure plasma jet to synthesize aqueous Au nanoparticles (AuNP). Special attention was paid to the different reaction dynamics and AuNP properties under AC and pulse-power-driven plasma jets (A-Jet and P-Jet, respectively). The morphology of the AuNP, optical emissions, and chemical reactions were analyzed. Further, a copper mesh was placed above the reaction cell to evaluate the role of electrons and neutral species reduction. A visible color change was observed after the A-Jet treatment for 30 s, while it took 3 min for the P-Jet. The A-Jet treatment presented a much higher AuNP growth rate and a smaller AuNP diameter compared with the P-Jet treatment. Further analysis revealed an increase in chemical concentrations (Cl- and H2O2) and liquid conductivity after plasma treatment, with a higher increased amplitude for the A-Jet case. Moreover, the electrons alone had little effect on AuNP generation, while neutral species showed a clear Au+ reduction effect, and a unique coupling effect between both reactions was observed. The different reaction dynamics between the A-Jet and P-Jet were attributed to their different local heating effects and different discharge power during the reaction.

scholarly journals Effects of O2 Addition on the Discharge Parameters and Production of Reactive Species of a Transferred Atmospheric Pressure Plasma Jet

2021 ◽  
Vol 11 (14) ◽  
pp. 6311
Author(s):  
Fellype Nascimento ◽  
Kleber Petroski ◽  
Konstantin Kostov
Keyword(s):  
Atmospheric Pressure ◽  
Light Emission ◽  
Noble Gas ◽  
Atmospheric Pressure Plasma ◽  
Plasma Jet ◽  
Reactive Species ◽  
Plasma Jets ◽  
Therapeutic Effects ◽  
Plastic Tube ◽  
Pressure Plasma

The therapeutic effects of atmospheric pressure plasma jets (APPJs) have been associated with the presence of reactive species, mainly the reactive oxygen and nitrogen ones, generated in this kind of plasmas. Due to that, many studies attempting to enhance the production of reactive species in APPJs have been performed. The employment of gas admixtures, usually mixing a noble gas with oxygen (O2) or water vapor, is one of the most common methods to achieve such goal. This work presents a study of how the addition of small amounts of O2 affects the electrical parameters and the production of reactive species in a transferred APPJ produced at the tip of a long and flexible plastic tube. The study was carried out employing helium (He) as the working gas and applying a high voltage (HV) in the form of amplitude-modulated sine waveform (burst mode). With this configuration it was possible to verify that the O2 addition reduces the discharge power and effective current, as a result of late ignition and shorter discharge duration. It was also found that the addition of O2 to a certain content in the gas admixture makes the light emission from oxygen atoms increase, indicating an increment in oxygen related reactive species in the plasma jet. However, at the same time the light emitted from hydroxyl (OH) and nitric oxide (NO) exhibits the opposite behavior, i.e., decrease, indicating a reduction of such species in the APPJ. For these reasons, the addition of O2 to the working gas seems to be useful for increasing the effectiveness of the plasma treatment only when the target modification effect is directly dependent on the content of atomic oxygen.

scholarly journals Extreme duty cycles in the acoustic signals of tiger moths: Sexual and natural selection operating in parallel

2021 ◽  
Author(s):  
Yohami Fernández ◽  
Nicolas J Dowdy ◽  
William E Conner
Keyword(s):  
Natural Selection ◽  
Mate Choice ◽  
Acoustic Communication ◽  
Duty Cycle ◽  
Sound Production ◽  
Acoustic Signals ◽  
High Duty Cycle ◽  
Duty Cycles ◽  
Tiger Moths

Abstract Sound production in tiger moths (Erebidae: Arctiinae) plays a role in natural selection. Some species use tymbal sounds as jamming signals avoiding bat predation. High duty cycle signals have the greatest efficacy in this regard. Tiger moth sounds can also be used for intraspecific communication. Little is known about the role of sound in the mating behavior of jamming species or the signal preferences underlying mate choice. We recorded sound production during the courtship of two high duty cycle arctiines, Bertholdia trigona and Carales arizonensis. We characterized variation in their acoustic signals, measured female preference for male signals that vary in duty cycle, and performed female choice experiments to determine the effect of male duty cycle on the acceptance of male mates. Although both species produced sound during courtship, the role of acoustic communication appears different between the species. Bertholdia trigona was acoustically active in all intraspecific interactions. Females preferred and ultimately mated with males that produced higher duty cycles. Muted males were never chosen. In C. arizonensis however, sound emissions were limited during courtship and in some successful matings no sound was detected. Muted and clicking males were equally successful in female mate-choice experiments, indicating that acoustic communication is not essential for mating in C. arizonensis. Our results suggest that in B. trigona natural and sexual selection may work in parallel, to favor higher duty cycle clicking.

scholarly journals Ionization waves in nanosecond pulsed atmospheric pressure plasma jets in argon

High Voltage ◽  
2021 ◽  
Author(s):  
Bangdou Huang ◽  
Cheng Zhang ◽  
Wenchao Zhu ◽  
Xinpei Lu ◽  
Tao Shao
Keyword(s):  
Atmospheric Pressure ◽  
Atmospheric Pressure Plasma ◽  
Plasma Jets ◽  
Pressure Plasma ◽  
Ionization Waves
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