Surface Dielectric Barrier Discharge Research Articles

Isotactic-polypropylene (iPP) wettability modified by surface DBD plasma

Abstract In this paper, atmospheric pressure plasma of ambient air was generated by surface dielectric barrier discharge (SDBD) device for the purpose of modifying the surface of isotactic-polypropylene (iPP). The effect of SDBD treatment time on the chemical and physical properties of iPP was studied using various analytical techniques including water contact angle (WCA), attenuated total reflection (ATR), Raman spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM). The results indicate that the hydrophilicity and the C=O bonds of the treated iPP were improved as observed, respectively, through WCA and FTIR analysis. The crystal structure was evaluated by Raman spectroscopy and XRD. It was found that the iPP chain was under microscopic stress, which affects its crystallinity degree depending on the duration of the treatment. Furthermore, the AFM analysis revealed that the surface roughness was substantially modified.

Self-powered organic pollutants degradation in wastewater by photocatalytic ozonation based on triboelectric nanogenerator

It is of great significance to explore innovative ways to degrade organic pollutants in wastewater. Here, for the first time, we report a self-powered photocatalytic ozonation water purification system for removing organic pollutants in aquatic environment. A rabbit fur-based rotary triboelectric nanogenerator (RR-TENG) is designed as the power supply of water purification system. As a new TENG-based ozone generation method, spark-surface dielectric barrier discharge (Spark-SDBD) is proposed, which is composed of spark discharge device and surface dielectric barrier discharge (SDBD) device in series and can generate ozone to a maximum concentration of 36.4 mg/m3. Rhodamine B and ciprofloxacin, two typical organic compounds, are selected as simulated pollutants in wastewater, and P25 particles loaded on nickel foam are used as the photocatalyst. Ozone is continuously introduced into the polluted solution through an aeration device, coupled with photocatalysis. Within 80 minutes, it can be observed that Rhodamine B has 100% decolorization and ciprofloxacin is degraded to 99%. This work broadens the field of water purification and provides an effective way to create a cleaner and safer aquatic environment.

Pilot-scale plasma activated water treatment for decontaminating romaine lettuce and steamed rice cakes

The study investigated the effects of pilot-scale plasma activated water (PAW) on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and indigenous mesophilic aerobic bacteria on romaine lettuce and steamed rice cake (SRC). PAW treatment was conducted by stirring 25 g of romaine lettuce and 80 g of SRC for 20–40 min at 195 rpm in 1 L of PAW, prepared by treating sterile distilled water with surface dielectric barrier discharge for 40 or 60 min. The microbial inactivation rates of foodborne pathogens and indigenous mesophilic aerobic bacteria ranged from 1.3 to 2.5 log on romaine lettuce and SRC, along with PAW generation time (P < 0.05). Inactivation rates of PAW generation time or treatment time against romaine lettuce and SRC were significantly different to the inactivation of distilled water treatments, respectively (P < 0.05). The pH, electrical conductivity, and hydrogen ion concentration correlated with nitrite and nitrate concentrations of PAW prepared at various PAW generation time. In situ pilot-scale PAW treatment also extended the shelf life of the romaine lettuce. The study demonstrates the feasibility of the pilot-scale PAW treatment to improve microbiological safety and its suitability of applying PAW to manufacture romaine lettuce and SRC products.

Maze-solving in a plasma system based on functional analogies to reinforcement-learning model.

Maze-solving is a classical mathematical task, and is recently analogously achieved using various eccentric media and devices, such as living tissues, chemotaxis, and memristors. Plasma generated in a labyrinth of narrow channels can also play a role as a route finder to the exit. In this study, we experimentally observe the function of maze-route findings in a plasma system based on a mixed discharge scheme of direct-current (DC) volume mode and alternative-current (AC) surface dielectric-barrier discharge, and computationally generalize this function in a reinforcement-learning model. In our plasma system, we install two electrodes at the entry and the exit in a square lattice configuration of narrow channels whose cross section is 1×1 mm2 with the total length around ten centimeters. Visible emissions in low-pressure Ar gas are observed after plasma ignition, and the plasma starting from a given entry location reaches the exit as the discharge voltage increases, whose route converging level is quantified by Shannon entropy. A similar short-path route is reproduced in a reinforcement-learning model in which electric potentials through the discharge voltage is replaced by rewards with positive and negative sign or polarity. The model is not rigorous numerical representation of plasma simulation, but it shares common points with the experiments along with a rough sketch of underlying processes (charges in experiments and rewards in modelling). This finding indicates that a plasma-channel network works in an analog computing function similar to a reinforcement-learning algorithm slightly modified in this study.

Three-electrode surface dielectric barrier discharge driven by repetitive pulses: streamer dynamic evolution and discharge mode transition

The streamer dynamic evolution and discharge mode transition of a three-electrode surface dielectric barrier discharge (SDBD) driven by repetitive pulses are studied experimentally and numerically for better plasma-mode control and optimized application. Spatial-temporal plasma morphologic features together with electro-optical behavior are utilized to analyze the streamer dynamic evolution and streamer-to-spark transition. To gain a deep insight into the physical mechanism of the discharge mode transition in repetitive pulses, a 2D fluid model combined with a 0D kinetic model is built and studied. A good agreement between the experimental measurements and numerical simulation in the propagation dynamics and voltage–current characteristics is achieved. The results show that the surface-streamer discharge in the form of primary and transitional streamers can transform into a surface-spark discharge characterized by the primary streamer, transitional streamer and spark phase in repetitive pulses under the high applied electric field. A high gas temperature will result in a large reduced electric field after the transitional streamer, which exceeds the ionization threshold and thus promotes the discharge mode transition. A high number of electrons can be released from the negative charges by oxygen atoms during the inter-pulse period, which is favorable for the re-ignition and ionization process of the subsequent pulse discharge.

Plasma characteristics and de-icing of three-electrode double-sided pulsed surface dielectric barrier discharge

Ice accumulation on aircraft can lead to aerodynamic performance degradation and even trigger security incidents. However, traditional surface dielectric barrier discharge (SDBD) reactors cannot work while covered by glaze ice. In the present work, a novel three-electrode double-sided SDBD is proposed and employed for glaze ice deicing. Compared with traditional SDBD reactor, three-electrode double-sided SDBD introduces an additional discharge area and grounding electrode. On one hand, the heat generated in the additional discharge area can melt the glaze ice covered on the high-voltage electrode, providing a discharge gap for the subsequent discharge. On the other hand, the introduction of the additional grounding electrode can also dramatically enhance the upper discharge and thermal effect. As a result, compared with the three-electrode single-sided SDBD and two-electrode double-sided SDBD, the three-electrode double-sided SDBD has the highest deposited energy, maximal temperature, and deicing rate. To further optimize the structural design, the effect of air gap length below the dielectric on three-electrode double-sided SDBD is investigated. And it is found that the best deicing performance can be obtained at the air gap length of 1 mm.

Deicing and status characteristics of dual-side pulsed surface dielectric barrier discharge

The deicing process and its status characteristics of dual-side pulsed surface dielectric barrier discharge (SDBD) are studied via electro-optical diagnostics, thermal properties, and numerical simulation. Experimental results show that the dual-side pulsed SDBD can remove the glaze ice compared to the traditional pulsed SDBD under the applied pulse voltage of 8 kV and a pulse frequency of 1 kHz. The maximal temperature of dual-side pulsed SDBD reaches 39.5 °C under the discharge time of 800 s, while the maximal temperature of traditional pulsed SDBD is still below ice point about −7.8 °C. Surface temperatures of dual-side pulsed SDBD demonstrate that the SDBD with a gap of 1 mm possesses prospects in deicing. The maximal surface temperature reaches 37.1 °C under the pulse of 8 kV after the discharge time of 90 s. Focusing on the thermal effect, a two-dimensional plasma fluid model is implemented, and the results also indicate that the dual-side pulsed SDBD with a gap of 1 mm produces a highest heat density among the three different configurations. Comparing the spatial-temporal evolutions of plasma on both dielectric sides, primary positive streamer has a longer propagation length of 8.6 mm than the secondary negative streamer, the primary negative streamer, and the secondary positive streamer, which induces a long heat covered area. Four stages of deicing process are analyzed through a series of electrical parameters under different covered ice conditions.

Numerical simulation of streamer, pressure wave, and vortex induced by nanosecond pulsed surface dielectric barrier discharges

In this study, a two-dimensional fluid model is employed to simulate the streamer, pressure wave, and vortex in surface dielectric barrier discharge driven by nanosecond pulse voltage (ns-SDBD). It comprises a numerical model with two interconnected modules: discharge dynamics and gas flow dynamics. These modules are coupled through the physical variables including ‘EHD force’, ‘thermal source’, ‘velocity field’, ‘gas temperature’, and ‘gas pressure’. Our research primarily focuses on the underlying physical mechanisms of pressure waves and vortices for plasma-based flow control. The generation of pressure waves is attributed to the rapid gas heating by pulsed discharge, whereas the formation and development of the vortex are related to the ionic wind (EHD effect) provided by the plasma. To thoroughly understand and optimize flow control performance, an investigation into the effects of various discharge parameters, such as voltage amplitude and polarity, is conducted. Additionally, several SDBD modules are arranged in series, each featuring a dual three-electrode configuration. Subsequently, the dynamic behaviors of multiple streamers, pressure waves, and vortices, along with their interactions, are explored.

Implementing water recirculation in a novel portable plasma-activated water reactor enhances antimicrobial effect against Escherichia coli

The need for sustainable and reliable decontamination methods is driven by concerns regarding antibiotic resistance, as well as environmental and cost-efficiency challenges associated with traditional methods. Plasma-activated water (PAW) holds significant promise as an innovative and eco-friendly decontamination method. Nevertheless, prior to industrial implementation of PAW-based decontamination devices, a deep understanding of the bacterial inactivation mechanisms and its interplay with PAW chemical composition is required. Advancing in this field requires interdisciplinary and collaborative research using standardized practices with cost-effective and shareable PAW reactors that are still missing today. Here, to this end, a portable PAW reactor, featuring a surface dielectric barrier discharge (SDBD) that operates in air, is presented. The gaseous and aqueous phases were chemically characterized by Fourier transform infrared (FTIR) absorption spectroscopy and vis-spectrophotometry, respectively. To assess PAW antimicrobial efficacy Escherichia coli was employed as a model organism on six different PAW samples for three different treatment times. The significance of water recirculation in controlling the chemical composition of PAW, altering the nitrogen species balance in favor of NO2−, is demonstrated. This chemical modification consequently enhanced the antimicrobial effectiveness of PAW, reaching a log reduction of ∼6. Exposing E. coli to equivalent concentrations of RONS to those found in PAW attained similar log-reductions, indicating that acidified nitrites are key to PAW antimicrobial activity. Through an innovative and portable design, this study illustrates the crucial role of water recirculation in tailoring PAW composition, leading to improved decontamination capabilities and establishing a key parameter for further optimization of PAW production.

Rapid Synthesis of Noble Metal Colloids by Plasma-Liquid Interactions.

The interactions between plasma and liquids cause complex physical and chemical reactions at the gas-liquid contact surface, producing numerous chemically active particles that can rapidly reduce noble metal ions. This study uses atmospheric-pressure surface dielectric barrier discharge (DBD) plasma to treat ethanol aqueous solutions containing noble metal precursors, and stable gold, platinum, and palladium colloids are obtained within a few minutes. To evaluate the mechanism of the reduction of noble metal precursors by atmospheric-pressure surface DBD plasma, the corresponding metal colloids are prepared first by activating an ethanol aqueous solution with plasma and then adding noble metal precursors. It is found that the long-lived active species hydrogen peroxide (H2O2) plays a dominant role in the synthesis process, which has distinct effects on different metal ions. When HAuCl4 and H2PdCl4 are used as precursors, H2O2 acts as a reducing agent, and AuCl4- and PdCl42- ions can be reduced to metallic Au and Pd. However, when AgNO3 is the precursor, H2O2 acts as an oxidising agent, and Ag+ ions cannot be reduced to obtain metal colloids because metallic Ag can be dissolved in H2O2 under acidic conditions. A similar phenomenon was also observed for the preparation of Pd colloid-PA with a plasma-activated ethanol aqueous solution using Pd(NO3)2 as a Pd precursor.

Filament analysis based on mathematical morphology of surface dielectric barrier discharges in N2/O2 mixtures

AbstractIn this paper, we measured the electrical potential distribution of surface dielectric barrier discharges (SDBD) caused by alternating voltage in synthetic air and nitrogen using the Pockels effect. It was shown that different potential distributions of filament thickness and length are generated in synthetic air and nitrogen. A filament analysis based on mathematical morphology was performed to quantify the geometric characteristics of the filaments produced in each gas atmosphere. The results show that the discharge filament thickness and the entropy in the filament direction depend on the oxygen ratio and the magnitude of the applied voltage.

Characteristics of annular surface dielectric barrier discharge with microsecond pulse under water-covered condition.

Surface dielectric barrier discharge (SDBD) has wide applications in flow control, wastewater treatment, and biomedicine. The dielectric surface of an SDBD actuator is generally attached to the water droplets during applications. Thus far, only a few studies have been conducted on the effects of water covering the dielectric surface on the discharge characteristics of SDBD. Therefore, the effects of water droplets on the discharge of an SDBD actuator based on a repetitive microsecond pulse power supply were investigated in this study. The results show that a filament micro-discharge channel forms between the light and dark regions at the internal edge of the SDBD high-voltage electrode and develops toward the center of the dielectric surface in the region without water droplet coverage. SDBD in the water-covered region was divided into two stages. This paper compares the electrical characteristics of SDBD with and without water droplet, and explores the electric field distortion effect of water droplet endpoints through 3D simulation.Based on the theories of water droplet polarization and gas discharge, the effects of water droplets on plasma development and surface charge accumulation under water-covered condition were analyzed. The water droplet plays a similar role as a "secondary electrode" during the discharge process.

In-Situ FTIR and Laser Induced Fluorescence RONS Characterization of Atmospheric Pressure Nanosecond-Pulsed Surface DBD Plasma for Indirect Treatments of E. Coli

We study the bactericidal efficacy of surface dielectric barrier discharge low-temperature plasma treatments, powered by nanosecond high voltage pulses. We achieve ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim $$\\end{document}4-log reduction in Escherichia coli population, after 10 min treatments, at a distance of 1.5 cm from the plasma surface. To investigate the reactive oxygen and nitrogen species (RONS) responsible for the bactericidal effect, we employ in-situ fourier transform infrared (FTIR) spectroscopy to measure a selection of relevant species, such as O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}, NO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}, N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O and N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_5$$\\end{document}. The measurements are taken under various relative humidity conditions to replicate the bacteria treatment environment. While RONS originating from nitrogen chemistry are detected, nitric oxide (NO), a pivotal molecule in nitrate production, is absent due to the sensitivity limitations of FTIR detection. To overcome this limitation, we employ laser induced fluorescence utilizing a picosecond-pulsed laser to measure the kinetics of NO produced by the plasma. Our results show that the NO concentration is smaller than 1 ppm and primarily localized near the plasma surface, with concentrations increasing proportionally with relative humidity. Notably, at a distance of 1.5 cm from the plasma surface, at which the E. coli is treated, the concentration of NO falls below 50 ppb. Although NO is pivotal in generating secondary reactive species within the plasma, our results suggest that it does not directly contribute to the bacteria inactivation process. Instead, other molecules, such as O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}, NO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}, and N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O, which are found in higher concentrations, may be responsible for the bactericidal properties observed in indirect plasma treatments.

Non-thermal plasma (NTP) treatment of Trigonella foenum-graecum L. seeds stimulates the sprout growth and the production of nutraceutical compounds

The possibility to stimulate the production of some nutraceutical properties of fenugreek (Trigonella foenum-graecum L.) sprouts by non-thermal plasma (NTP) processing of the seeds in different conditions was studied. The non-thermal plasma used in this work was a surface dielectric barrier discharge. Two types of processing were performed: direct NTP treatment and NTP with a cover treatment, to simulate the processing of packaged seeds. For all treatments, the effect of pre-soaking of the seeds was studied as well. The analyses of the seeds after processing indicated an increase of the hydrophilicity of their surface for NTP direct treatment as resulted from the water contact angle measurements, which could be due to the strong etching evidenced by scanning electron microscopy imaging. A significant (p < 0.05) increase of the seedling growth, by up to 50%, was found especially for the pre-soaked seeds. These results were correlated with the increase of chlorophyll pigments concentrations, with higher concentrations in the case of NTP direct treatment than for the NTP with cover treatments. Direct NTP treatment for 30 s of dry seeds led to the highest increase of the flavonoid concentration of about three times compared to that obtained for untreated seeds. For the polyphenols and antioxidant activity, NTP with cover treatments proved to be better, with a significant increase, especially for 90 s treatment of the pre-soaked seeds. All the results indicate the possibility of tuning the nutraceutical properties of fenugreek sprouts by NTP treatment.

Efficiency of cold atmospheric plasma under ozone (O3) and nitrogen oxide (NOx) regimes on the degradation of aflatoxins and ochratoxin A in solid state and in spiked pistachio kernels

Mycotoxins are the primary contaminants in food that have a significant impact on global food safety and security. Cold atmospheric plasma (CAP) has demonstrated significant potential in reducing mycotoxins among innovative technologies. This study aimed to assess the effectiveness of a surface dielectric barrier discharge (SDBD) CAP system in reducing aflatoxins B1 (AFB1), B2 (AFB2), G1 (AFG1), G2 (AFG2), and ochratoxin A (OTA). The distinctive feature of the device here used was the ability to operate at two different powers, resulting in two different plasma reactive species ambients: ozone (O3) and nitrogen oxides (NOx) regimes. CAP treatments exhibited a significant reduction of all investigated pure mycotoxins, which was regime, molecule chemical structure, distance from the source and time-dependent. In particular, O3 regime was more effective (AFB1 and AFG1 99%, AFB2 and AFG2 60%, OTA 70% reduction, respectively, at 60 min, 4 cm distance from the plasma source). As low-moisture foods pistachio kernels (Pistacia vera L. seeds) were selected to evaluate the matrix effect. As expected, the mycotoxins were reduced to a much lesser extent than pure molecules. Worthy of note was the 23% reduction of OTA. To our best knowledge, this is the first investigation about OTA degradation in pistachio food matrix by cold plasma. It should also be noted that the pistachios have been artificially contaminated with spots of a mixture of mycotoxins, to best represent a probable real contamination.

A Numerical Investigation of Supersonic Combustion Flow Control by Nanosecond-Pulsed Actuations

The efficiency of supersonic combustion is largely dependent on inlet and injection parameters. Additional energy input is required in some off-design conditions, and nanosecond discharge actuation can be a solution. In the present study, a phenomenological model of a nanosecond-pulsed surface dielectric barrier discharge (NS-SDBD) actuator was developed to analyze the combustion enhancement effect for a supersonic combustor with transverse H2 injection. A seven-reaction H2–air combustion model was adopted for the numerical simulation. Dynamic mode decomposition (DMD) was employed to acquire temperature perturbation in spatial and temporal domains. The results show that the actuator provides additional temperature-increment and species transportation through compression waves. The combustion enhancement effect is mainly attributed to the flow perturbation in the shear layer, which promotes the turbulent diffusion of fuel. Given the same power input, the combustion efficiency at the shockwave reflection point is increased by 17.5%, and the flame height is increased by 15.4% at its maximum.

Influence of Dielectric Material Thickness on the Formation of Atmospheric Plasma

This research examines the effects of dielectric material thickness and geometry on the formation of surface dielectric barrier discharge (DBD) in air. To initiate the discharge process, electrodes are connected to a high voltage source, ionizing the surrounding air and forming a thin layer of plasma near the dielectric material. The electrohydrodynamic (EHD) forces generated during this process are measured and analyzed to determine the influence of dielectric thickness and geometry on plasma formation. This study provides a more comprehensive understanding of the roles that dielectric material properties play in atmospheric plasma generation, contributing to potential optimization in the application of plasma-based technologies.

Ammonia synthesis using atmospheric pressure fluidized bed plasma

In recent years, extensive research has been conducted on ammonia synthesis using catalysts under mild conditions and by combining plasma with the catalysts. Increasing the contact area between the catalyst surface and atmospheric pressure dielectric barrier discharge (DBD) is crucial for improving the ammonia synthesis efficiency. In this study, we present a fluidized bed dielectric barrier discharge (FB-DBD) method that can be used to form FB-DBD plasma through the electrohydrodynamics of DBD discharge without a feed gas. We performed ammonia synthesis experiments using our FB-DBD reactor. The results indicate that the FB-DBD plasma can achieve an energy yield of 5.9 g-NH3/kWh, which is about twice higher than that of conventional DBD plasma. Consequently, it can be implemented in various applications as a new reaction field between solids and gases where surface reactions are predominant.

Comparison of Plasma-Polymerized Thin Films Deposited from 2-Methyl-2-oxazoline and 2-Ethyl-2-oxazoline: I Film Properties.

Poly(2-oxazoline) is a promising new class of polymeric materials due to their antibiofouling properties and good biocompatibility. Poly(2-oxazoline) coatings can be deposited on different substrates via plasma polymerization, which can be more advantageous than other coating methods. The aim of this study is to deposit poly(2-oxazoline) coatings using a surface dielectric barrier discharge burning in nitrogen at atmospheric pressure using 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline vapours as monomers and compare the film properties. For the comparison, the antibacterial and cytocompatibility tests were peformed according to ISO norms. The antibacterial tests showed that all the deposited films were highly active against Staphylococcus aureus and Escherichia coli bacteria. The chemical composition of the films was studied using FTIR and XPS, and the film surface's properties were studied using AFM and surface energy measurement. The cytocompatibility tests showed good cytocompatibility of all the deposited films. However, the films deposited from 2-methyl-2-oxazoline exhibit better cytocompatibility. This difference can be explained by the different chemical compositions and surface morphologies of the films deposited from different monomers.

Study on Aerodynamic Drag Reduction by Plasma Jets for 600 km/h Vacuum Tube Train Sets

In order to break through the speed bottleneck, researchers envision using tubes to cover high-speed maglev trains and extract some of the air inside the tubes, creating a low-density environment on the ground, greatly reducing the aerodynamic drag of the trains, and in a relatively economical and feasible way, making high subsonic (600 km/h and above) and even supersonic ground transportation possible. The faster the running speed of high-speed trains, the greater the impact of aerodynamic drag on their energy consumption. Studying the aerodynamic characteristics of trains with a speed of 600 km/h can help optimize the aerodynamic shape of the train, reduce aerodynamic drag, and reduce energy consumption. This has positive implications for improving train energy efficiency, reducing energy consumption, and environmental impact. This paper adopts the numerical simulation method to study the drag reduction effect of the plasma arrangement and different excitation speeds on the train set in four positions when the incoming wind speed is 600 km/h, to analyze the mechanism of drag reduction, and then to analyze the combination of working conditions in order to investigate the drag reduction effect of plasma on the vacuum tube train set with an ambient pressure of 10,000 Pa. The findings demonstrate that the plasma induces the directional flow of the gas close to the wall to move the flow separation point backward and delay the separation of the flow, thereby reducing the front and rear differential pressure drag of the train set and lowering the aerodynamic drag coefficient of the entire train. The plasma arrangement is located at the rear of the flow separation point and in close proximity to the flow separation point. The pneumatic drag reduction effect peaks when the excitation speed reaches 0.2 times the train speed and the pneumatic drag reduction ratio is around 0.88%; the pneumatic drag reduction ratio of the rear car peaks when the excitation speed reaches 0.25 times the train speed and the pneumatic drag reduction ratio is 1.62%. The SDBD (Surface Dielectric Barrier Discharge) device is installed at the flow separation point around the nose tip of the rear car.