Pressure Plasma Processing Research Articles

Interactions of Non-Thermal Atmospheric Pressure Plasma with Solid and Liquid Food Systems: A Review

Non-equilibrium atmospheric pressure plasma processes combine several advantages such as non-thermal operation and high antimicrobial activity and are thus proposed to be a prospective alternative to traditional food preservation methods, which suffer from undesired alterations of food quality and a lack of acceptance by the consumer. This review summarizes the latest research work in the field of food science and technology dealing with the application of plasma processes on solid and liquid foodstuff. Starting with the historical background of plasma, the basic principles of plasma generation and of the complex plasma chemistry are highlighted and insights into plasma–surface and plasma–liquid interactions are given. Important research results in terms of plasma application on foods are presented with emphasis on the impact of the food matrix on microbial inactivation. Furthermore, the results of recent studies about the behavior of food quality-related components and attributes during plasma exposure are presented.

Engineering of Composite Organosilicon Thin Films with Embedded Silver Nanoparticles via Atmospheric Pressure Plasma Process for Antibacterial Activity

An innovative antibacterial thin film with imbedded silver nanoparticles (AgNPs) is investigated through atmospheric pressure plasma deposition. The process is based on a single-step fabrication of nanocomposite films where AgNPs are fed directly into the discharge zone. The morphology and stoichiometry of the thin films, characterized with SEM/EDX, GD-OES, and XPS, can be tailored by the plasma parameters and the quantity of introduced AgNPs. An exceptional 32 at% of AgNPs is reached in the work. The antibacterial assays using Escherichia coli and Staphylococcus aureus strains show effective antibacterial activity of the films and indicate that the fabrication of nanocomposite films using atmospheric pressure plasma represents a feasible way to overcome the issue of device related infection.

A Methacrylic Anhydride Difunctional Precursor to Produce a Hydrolysis-Sensitive Coating by Aerosol-Assisted Atmospheric Plasma Process

In this paper, we focused our attention on the elaboration of a hydrolyzable plasma-polymer produced by aerosol-assisted atmospheric pressure plasma process. A dielectric barrier discharge (DBD) was hence fed with a commercial methacrylic anhydride precursor – bearing an anhydride hydrolyzable function and two methacrylates groups aiming at producing a highly cross-linked deposit – to produce thin coatings of plasma-polymerized (pp) methacrylic anhydride. IR and NMR were performed to highlight the retention of the hydrolyzable group. After immersion in water, mass spectrometry analysis was conducted on the aqueous medium to characterize the end-products and consequently confirm the occurrence of a hydrolytic degradation. A huge 80% thickness decrease was finally pointed out by nanoscratch measurements after 10 days.

The morphology and chemistry evolution of fused silica surface after Ar/CF4 atmospheric pressure plasma processing

In order to reveal the plasma etching processes on fused silica, the surface characterizations of fused silica after Ar/CF4 atmospheric pressure plasma processing were investigated. The morphology and chemistry evolution of fused silica surface were analyzed by AFM and XPS respectively. The AFM micrographs exhibited the three-dimensional surface topography and the RMS roughness changed with the increase of the material removal depth. The surfaces appeared to become smoother when the plasma etching occurred on the surface top layer. However, after the chemically modified layer was removed, etching resulted in the formation of a series of pits. During extended etching, the individual pits coalesced with one another, and the coalescence provided a means of reducing the depth of subsurface damage and the RMS roughness. The XPS results illustrated that small amount of radicals including C-CFn and CF-CFn could be introduced onto the fused silica surface during the Ar/CF4 plasma process, the fluorocarbon radicals were generated during CF4 plasma ionization. And the changes in relative concentration of the fluorocarbon radicals C-CFn with the removal depth were also studied.

Development of conductive coated Polyether ether ketone (PEEK) filament for structural health monitoring of composites

Taking full advantage of its high temperature resistance and high elongation properties, conductive coated Polyether ether ketone (PEEK) filament yarn can be used as a textile-based electro-conductive functional element, especially as a strain sensor. This paper describes the development of electric conductivity on an inert PEEK filament surface by applying silver (Ag) metallic layers using a wet chemical procedure. To ensure good adhesion properties of the Ag layer, the PEEK monofilament surface is treated with an atmospheric pressure plasma process and a subsequent coating of a polyamine based adhesion promoter. Measurements of electrical resistance of Ag coated PEEK filament yarns are performed before and after their integration into the textile reinforced thermoplastic composite . The electro-mechanical characterisations show the potential of Ag-coated PEEK for structural health monitoring in textile-reinforced composites. Furthermore, the electro-mechanical behaviour of Ag coated PEEK is analysed mathematically and compared with experimental values.

Study on Atmospheric Pressure Plasma Processing of Fused Silica

In order to get ultra-smooth surface without subsurface damage efficiently for fused silica, the atmospheric pressure plasma processing (APPP) is developed. It is based on chemical reaction between active radicals excited by plasma and workpiece surface atoms, so the subsurface damage caused by contact stress can be avoided and atomic-level precision machining can be achieved. In this paper, the influence on material removal function by the key factors of APPP including the flow rate of reaction gases, input power, and processing distance are discussed. In addition, by the regression model a quantitative mathematical model of the material removal function of the atmospheric pressure plasma processing on fused silica is established. And this model is verified by experimental data.

Atmospheric pressure plasma treated carbon fibre weave: A flexible approach to wound monitoring

Atmospheric pressure plasma processing has been investigated as a rapid means of activating carbon fibre thread for use in the manufacture of smart bandages. Ferrocyanide and ruthenium hexamine were used as redox probes to assess the influence of plasma exposure time on the electroanalytical performance of material to be incorporated within prototype wound dressings. Ion exchange of the ruthenium at the carbon interface was observed and was attributed to the plasma induced creation of surface carboxyl groups. These had the effect of improving electron transfer kinetics and surface wetting. The applicability of the modified material for wound monitoring was critically assessed through examining the direct response in whole blood.

Surface modification of cellulose via atmospheric pressure plasma processing in air and ammonia–nitrogen gas

Changes to the surface properties of cellulose induced by a dielectric barrier discharge (DBD) plasma operating at atmospheric pressure in both air and an ammonia/nitrogen gas mixture have been analysed using water contact angle, XPS and AFM. The water contact angle for cellulose processed in air decreased significantly after exposure to DBD. XPS indicated that changes in surface chemistry are not the main cause of this reduction in wettability. AFM studies clearly show that a significant increase in surface roughness results from the plasma treatment and that there is a correlation between the increased Ra/Rq values for higher applied power and processing cycle numbers and the associated changes observed in the water contact angles. When cellulose is plasma processed in a v/v 10%NH3/90%N2 gas mixture the surface undergoes functionalisation with nitrogen groups as indicated by XPS analysis. Specifically, the formation of both amine (NH2) and to a lesser extent amide (CONH2) moieties is evident. The contact angle results for these samples indicate an initial decrease in wettability followed by relaxation to slightly higher values consistent with a degree of surface relaxation post-processing. The corresponding AFM data indicate that whereas the slight increase in surface roughness contributes to the change in hydrophilicity, unlike processing in air, it is not the only factor involved. In this case, it is the modified surface chemistry that has the greatest influence for cellulose processed under these conditions. Hence, despite its inherently high oxygen content, cellulose can be modified using atmospheric plasma in air and 10%NH3/90%N2 to produce modified surface properties known to actively promote biological cell adhesion. This offers a route to enhance the role that this abundant biomaterial can play as a construct for tissue engineering and related applications.

Development of local ambient gas control technologies for atmospheric MEMS process

We report on a local ambient gas control technologies for atmospheric pressure plasma process using our new curtain gas structure. First, local ambient gas control with the curtain gas structure was investigated by computational fluid dynamic code. After confirmation of the feasible cleanness level with this structure, which is comparable to impurity level in semiconductor grade material gas (below 1 ppm), we fabricated a prototype apparatus. Measuring gas distribution by a gas analyzer, local ambient gas control was confirmed experimentally. Next, we attempted H 2 /He plasma generation in open air with H 2 concentration even above explosive limit in air (4.1 %) and achieved stable glow discharge with H 2 concentration of 0–40 %. In addition, reduction of copper oxides was demonstrated by H2 plasma exposure. These results show high potential of our method for atmospheric MEMS processes.

Designing Atmospheric-Pressure Plasma Sources for Surface Engineering of Nanomaterials

Atmospheric-pressure plasma processing techniques emerge as efficient and convenient tools to engineer a variety of nanomaterials for advanced applications in nanoscience and nanotechnology. This work presents different methods, including using a quasi-sinusoidal high-voltage generator, a radio-frequency power supply, and a uni-polar pulse generator, to generate atmospheric-pressure plasmas in the jet or dielectric barrier discharge configurations. The applicability of the atmospheric-pressure plasma is exemplified by the surface modification of nanoparticles for polymeric nanocomposites. Dielectric measurements reveal that representative nanocomposites with plasma modified nanoparticles exhibit notably higher dielectric breakdown strength and a significantly extended lifetime.

微结构光学零件的大气等离子体数控加工

To process micro-structured surface optical elements without surface damage and subsurface damage in higher efficiency,a numerical control system for Atmospheric Pressure Plasma Processing(APPP) was established.The design of a system platform,APPP process characteristics and numerical control process were investigated.First,according to the principle and requirements of the APPP,the numerical control system composition was presented.Then,by taking the processing of fused silica by He/SF6/O2 as an example,the controllability of the process as well as multi-parameter process characteristics were explored using the plasma torch with a needle electrode,and the removal function under this condition was fitted.Finally,the entire realization process of the numerical control machining for the APPP was proposed.Experimental results indicate that the sine structure with an amplitude of 150 nm and wavelength of 6 mm can be processed on a flat fused silica surface by this system,which verifies the feasibility of the numerical control system and achieves the deterministic processing of complex optical surfaces.

Development of the Local Ambient Gas Control Technology and its Application to Atmospheric Pressure Plasma Processes

Local ambient gas control technologies for atmospheric pressure plasma processes using a new curtain gas structure have been developed. The local ambient gas control was studied theoretically and experimentally. Safe and clean process conditions (reactive gas leakage below 0.1 vol.% and air contamination below 10ppm) were achieved in open air. H2 plasma was generated with H2 concentrations above the explosive limit (4.1% in air) successfully. As an application, Cu reduction and SiO2 etching were demonstrated. These results indicate that our local ambient gas control technologies have adequate potential for atmospheric pressure plasma processes.

Polymer films with surfaces unmodified and modified by non-thermal plasma as new substrates for cell adhesion

The surface properties of biomaterials, such as wettability, polar group distribution, and topography, play important roles in the behavior of cell adhesion and proliferation. Gaseous plasma discharges are among the most common means to modify the surface of a polymer without affecting its properties. Herein, we describe the surface modification of poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) films using atmospheric pressure plasma processing through exposure to a dielectric barrier discharge (DBD). After treatment the film surface showed significant changes from hydrophobic to hydrophilic as the water contact angle decreasing from 95° to 37°. All plasma-treated films developed more hydrophilic surfaces compared to untreated films, although the reasons for the change in the surface properties of PS and PMMA differed, that is, the PS showed chemical changes and in the case of PMMA they were topographical. Excellent adhesion and cell proliferation were observed in all films. In vitro studies employing flow cytometry showed that the proliferation of L929 cells was higher in the film formed by a 1:1 mixture of PS/PMMA, which is consistent with the results of a previous study. These findings suggest better adhesion of L929 onto the 1:1 PS/PMMA modified film, indicating that this system is a new candidate biomaterial for tissue engineering.

Comparison of Nonthermal Plasma Processes on the Surface Properties of Polystyrene and Their Impact on Cell Growth

The initial adhesion and spreading of cells are crucial factors for the successful performance of a synthetic biomaterial used for cell culture disposables or human medical devices (e.g., implants). Surface properties which allow the control of the attachment of cells are decisive for the acceptance of the provided material. Hence, different surface preparation techniques are used to equip surfaces with functional groups to improve initial surface interactions. In this paper, polystyrene (PS) surfaces were modified by using different nonthermal plasma processes. In particular, low-pressure plasma and atmospheric-pressure plasma were applied to modify surfaces or to deposit thin films on surfaces. Furthermore, the behaviors of human osteoblastic cells with respect to cell viability and cell growth on differently plasma treated PS surfaces are investigated. A comparison is made between plasma-grafted PS and commercially available PS-such as tissue-culture PS and Primaria. The cell studies were accompanied by surface analysis comprising atomic force microscopy, determination of surface energies, and X-ray photoelectron spectroscopy measurements. This work demonstrates that the functionalization of PS substrates by applying low-pressure and atmospheric-pressure plasma processes are equally effective in the improvement of cell attachment and proliferation. Furthermore, it is shown that the enhanced metabolic activity and spreading behavior of osteoblastic cells correlate well with an increase in surface wettability and the introduction of polar oxygen- and/or nitrogen-containing functional groups after plasma treatment.

Low Friction Property of Diamond-Like Carbon Coating Films and Oxygen Transmission Ratio of Amorphous Carbon Films Deposited by Advanced Coating Processes

The topics of the applied technology of amorphous carbon film to reduce friction using diamond-like carbon (DLC) coated by the vacuum arc ion plating process and to improve the gas barrier property using the amorphous carbon film by the atmospheric pressure plasma process are introduced with the basic experimental results. For reducing friction, the super low friction coefficient below 0.01 has been found when the tetrahedral amorphous carbon coating deposited by T-shape filtered arc deposition method [ta-C(T)] was evaluated the friction property under oleic acid lubrication at pure sliding condition. It was thought that the low share strength tribofilm composed of water and oleic acid mono-layer seemed to be formed on the sliding interface. For gas barrier performance, the amorphous carbon film deposited by the atmospheric pressure plasma chemical vapour deposition (CVD) technique on poly(ethylene terephthalate) (PET) substrate was improved the oxygen transmission ratio (OTR) around 30% compared with that of uncoated PET substrate. These advanced performance obtained by the optimum material combination of DLC with lubricant and the original atmospheric pressure plasma CVD technique are expected to be applied on the actual application for the different types of the industrial fields in near future.

Effect of atmospheric pressure plasma treatment on the desizing and subsequent colour fading process of cotton denim fabric

In this article, the performance of atmospheric pressure plasma treatment in the desizing of grey cotton denim fabric followed by an enzymatic colour fading process was studied. Four atmospheric pressure plasma processing parameters, namely, treatment time, ignition power, reactive gas (oxygen) concentration and jet distance were considered for desizing. In order to investigate the optimum conditions (based on weight change) for atmospheric pressure plasma treatment, an orthogonal array testing strategy was used. The optimum conditions for atmospheric pressure plasma treatment in this study were: treatment time, 5 s/mm; ignition power, 160 W; oxygen concentration, 1%; and jet distance, 3 mm. The level of importance of atmospheric pressure plasma processing parameters based on the orthogonal array testing strategy analysis was in the order: jet distance > ignition power > oxygen concentration > treatment time, and the effect of each processing factor is also discussed. In addition, the desizing effect induced by atmospheric pressure plasma treatment was compared with conventional enzyme desizing treatment. The resultant performance properties were also compared. After conducting desizing with atmospheric pressure plasma treatment, the cotton denim fabric was subjected to an enzymatic colour fading process. The colour fading effect was found to be more significant when compared with the conventional enzymatic colour fading process.

On the Use of Atmospheric Pressure Plasma for the Bio-Decontamination of Polymers and Its Impact on Their Chemical and Morphological Surface Properties

Low temperature atmospheric pressure plasma processes can be applied to inactivate micro-organisms on products and devices made from synthetic and natural polymers. This study shows that even a short-time exposure to Ar or Ar/O2 plasma of an atmospheric pressure plasma jet leads to an inactivation of Bacillus atrophaeus spores with a maximum reduction of 4 orders of magnitude. However, changes in the surface properties of the plasma exposed material have to be considered, too. Therefore, polyethylene and polystyrene are used as exemplary substrate materials to investigate the effect of plasma treatment in more detail. The influence of process parameters, such as type of operating gas or jet-nozzle to substrate distance, is examined. The results show that short-time plasma treatment with Ar and Ar/O2 affects the surface wettability due to the introduction of polar groups as proofed by X-ray photoelectron spectroscopy. Furthermore, atomic force microscopy images reveal changes in the surface topography. Thus, nanostructures of different heights are observed on the polymeric surface depending on the treatment time and type of process gas.

Improving the pilling property of knitted wool fabric with atmospheric pressure plasma treatment

Knitted wool fabrics are very easy to pill during wear and use. In this study, knitted wool fabrics were treated with atmospheric pressure plasma (APP), a completely dry treatment, using plasma jet with helium and oxygen as carrier and reactive gas, respectively, under various processing parameters: (i) jet-to-substrate distance; (ii) oxygen flow rate; and (iii) treatment time. This paper reports the study of how these APP processing parameters influence pilling property of knitted wool fabrics. After APP treatment, pilling property of knitted wool fabrics was evaluated by standard testing method for pilling (EN ISO 12945-1; ICI pilling box method). Also, a conventional wet anti-pilling treatment (with an anti-pilling agent) was carried out on knitted wool fabrics in order to compare anti-pilling effect of APP (dry treatment) and anti-pilling agent (wet treatment). Experimental results revealed that the APP treatment can greatly improve anti-pilling performance without adverse effect like yellowing. Scanning electron microscopy revealed that surface etching effect induced by APP treatment could be one of the reasons of improved anti-pilling property of knitted wool fabrics. Various processing parameters provide different degrees of etching on wool fibre surface. Meanwhile, no fabric shrinkage was noted in the APP treated knitted wool fabric but about 5% shrinkage in area was noted in fabric treated with anti-pilling agent.

Trends in surface engineering of biomaterials: atmospheric pressure plasma deposition of coatings for biomedical applications

Cold plasma processes for surface engineering of biomaterials and biomedical devices are traditionally performed at low pressure; more and more, though, surface modification plasma processes at atmospheric pressure are also gaining popularity. This short review is aimed to list briefly atmospheric pressure plasma processes reported, in the last decade, for adapting the surface of materials to the best interactions with cells, bacteria and biomolecules.

Deposition of Organosilicon Coatings by a Non‐Equilibrium Atmospheric Pressure Plasma Jet: Design, Analysis and Macroscopic Scaling Law of the Process

AbstractSilicon oxide based (SiOxCyHz, noted SiOx) coatings are often used in surface engineering for microelectronics, corrosion resistance, barrier to gas permeation through polymeric materials, etc… SiOx coatings can be efficiently deposited by non‐equilibrium atmospheric pressure plasma processes, such as DBD or plasma jets. In the present study, the design of experiment (DoE) methodology was used to investigate the influence of process parameters on the characteristics of organosilicon coatings deposited by a non‐equilibrium atmospheric pressure plasma jet (APPJ) from hexamethyldisiloxane (HMDSO) and air mixtures. The results obtained were used to create an empirical model to predict the chemical composition of coatings. Among 11 process parameters, the 3 parameters which exhibited the strongest effect on the coating composition were the torch speed, the substrate to nozzle distance and the number of scans. Auger spectroscopy revealed that the carbon content of the thin films was as low as 6 ± 1.7% and AFM analysis showed that smooth coatings (Ra ∼ 2 nm) were obtained even at high dynamic growth rates (∼1 000 nm · m · min−1). A tentative macroscopic scaling law was also formulated to correlate our results with the available literature data. magnified image