Non-thermal Atmospheric Plasma Research Articles

Plasma treatment of dentin surfaces for improving self-etching adhesive/dentin interface bonding

This study is to evaluate plasma treatment effects on dentin surfaces for improving self-etching adhesive and dentin interface bonding. Extracted unerupted human third molars were used after crown removal to expose dentin. One half of each dentin surface was treated with atmospheric non-thermal argon plasmas, while another half was untreated and used as the same tooth control. Self-etching adhesive and universal resin composite was applied to the dentin surfaces as directed. After restoration, the adhesive–dentin bonding strength was evaluated by micro-tensile bonding strength (μTBS) test. Bonding strength data was analyzed using histograms and Welch׳s t-test based on unequal variances. μTBS test results showed that, with plasma treatment, the average μTBS value increased to 69.7±11.5MPa as compared with the 57.1±17.5MPa obtained from the untreated controls. After 2 months immersion of the restored teeth in 37°C phosphate buffered saline (PBS), the adhesive–dentin bonding strengths of the plasma-treated specimens slightly decreased from 69.7±11.5MPa to 63.9±14.4MPa, while the strengths of the untreated specimens reduced from 57.1±17.5MPa to 48.9±14.6MPa. Water contact angle measurement and scanning electron microscopy (SEM) examination verified that plasma treatment followed by water rewetting could partially open dentin tubules, which could enhance adhesive penetration to form thicker hybrid layer and longer resin tags and consequently improve the adhesive/dentin interface quality.

Hydrophobicity attainment and wear resistance enhancement on glass substrates by atmospheric plasma-polymerization of mixtures of an aminosilane and a fluorocarbon

Mixtures of different proportions of two liquid precursors were subjected to plasma-polymerization by a non-thermal atmospheric jet plasma system in a search for a coating that achieves a hydrophobic character on a glass substrate and enhances its wear resistance. 1-Perfluorohexene (PFH) was chosen as a low-surface-energy precursor to promote a hydrophobic character. Aminopropyltriethoxysilane (APTES) was chosen for its contribution to the improvement of wear resistance by the formation of siloxane bonds. The objective of this work was to determine which of the precursors’ mixtures that were tested provides the coating with the most balanced enhancement of both hydrophobicity and wear resistance, given that coatings deposited with fluorocarbon-based precursors such as PFH are usually low in resistance to wear and coatings deposited with APTES are generally hydrophilic. The coatings obtained were analyzed by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infra-Red (FTIR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), static Water Contact Angle (WCA) measurements, tribological ball-on-disc tests and contact profilometry. A relationship between the achievement of a hydrophobic character and the modifications to roughness and surface morphology and the incorporation of fluorocarbon groups in the surface chemistry was observed. Also, it was seen that the wear resistance was influenced by the SiOSi content of the coatings. In turn, the SiOSi content appears to be directly related to the percentage of APTES used in the mixture of precursors. The best conjunction of hydrophobicity and wear resistance in this work was found in the sample that was coated using a mixture of APTES and PFH in proportions of 75 and 25%, respectively. Its WCA (100.2±7.5°) was the highest of all samples that were measured and more than three times that of the uncoated glass (31±0.7°). This sample underwent a change from a hydrophilic to a hydrophobic character. It also had the lowest wear rate of the hydrophobic samples obtained in this work, with a reduction of 28.8% in the wear rate of the uncoated glass.

Effects of non-thermal atmospheric pressure air plasma on gene expression at SLAtreated titanium surfaces

Dental implants manufacturers have developed high hydrophilic and rough implant surfaces which in turn exhibited better osseointegration than conventional ones. Based on in vitro studies, sand blast, large grit, acid etching(SLA)-treated surfaces with microstructural characteristics may promote the process of osseointegration. But when the SLA surface is kept dry in the air, it becomes hydrophobic. Appropriate non-thermal atmospheric pressure air plasma jet(air-NTAPPJ) processes render surfaces hydrophilic. The purpose of this research is to air-NTAPPJ on SLA surface treatment to improve the osteogenic functionality. The experiment was carried out through the a cytotoxicity assay and real-time reverse transcriptase-polymerase chain reaction(RT-PCR). The results were that the cell viability and gene expression of ALP, OCN, OPN, and Runx-2 of rMSC enhanced by air-NTAPPJ treated. Thus, air-NTAPPJ application can lead to an improved osseointegration.

Qualitative gas temperature distribution in positive DC glow corona using spectral image processing in atmospheric air

An experimental method of determining a qualitative two-dimensional image of the gas temperature in stationary atmospheric nonthermal plasma by spectral image processing was presented. In the experiment, a steady-state glow corona discharge was generated by applying a positive DC voltage to a rod-plane electrode in synthetic air. The changes in the gas temperature distribution due to the amplitude of applied voltage and the ambient gas pressure were investigated. Spectral images of a positive DC glow corona were taken using a gated ICCD camera with ultranarrow band-pass filters, corresponding to the head and tail of a N2 second positive system band (0–2). The qualitative gas temperature was obtained from the emission intensity ratio between the head and tail of the N2 second positive system band (0–2). From the results, we confirmed that the gas temperature and its distribution of a positive DC glow corona increased with increasing applied voltage. In particular, just before the sparkover voltage, a distinctly high temperature region was formed in the positive DC glow at the tip of the rod electrode. In addition, the gas temperature decreased and its distribution spread diffusely with decreasing ambient gas pressure.

Effects of the electrical excitation signal parameters on the geometry of an argon-based non-thermal atmospheric pressure plasma jet.

A non-thermal atmospheric pressure argon plasma jet for medical applications has been generated using a high-voltage pulse generator and a homemade dielectric barrier discharge (DBD) reactor with a cylindrical configuration. A plasma jet of about 6 cm of length has been created in argon gas at atmospheric pressure with an applied peak to peak voltage and a frequency of 10 kV and 50 kHz, respectively. The length and the shape of the created plasma jet were found to be strongly dependent on the electrode setup and the applied voltage and the signal frequency values. The length of the plasma jet increases when the applied voltage and/or its frequency increase, while the diameter at its end is significantly reduced when the applied signal frequency increases. For an applied voltage of 10 kV, the plasma jet diameter decreases from near 5 mm for a frequency of 10 kHz to less than 1 mm at a frequency of 50 kHz. This obtained size of the plasma jet diameter is very useful when the medical treatment must be processed in a reduced space.PACS 200852.50.Dg; 52.70.-m; 52.80.-s

Comparison of $\mu $ s- and ns-Pulse Gliding Discharges in Air Flow

Pulsed power can provide instantaneously high power density to generate atmospheric nonthermal plasma in open air. In this paper, using two power supplies including a μs-pulse generator with a rise time of 300 ns and a pulsewidth of 5 μs and a ns-pulse generator of a rise time of 70 ns and a pulsewidth of 100 ns, pulsed gliding discharges are created with point-to-point electrodes in open air. Discharge images with these two generators under different flow rates are presented for a brief comparison of μsand ns-pulse gliding discharges in air flow.

Dental applications of non-thermal atmospheric pressure plasma: a review

等离子体(plasma)是继气体、液体和固体之后的第四种物质形态.1879年由William Crookes发现,1928年Irving Langmuir将其正式命名为等离子体.宇宙中99.9％的物质都是等离子体,如火焰、极光、雷电、恒星等[1].以往人工获得等离子体的技术难度较大,需要真空系统,设备体积巨大,应用范围受限.随着等离子体技术研究的发展,大气压等离子体源不再需要昂贵的真空系统,设备体积缩小,越来越多的学者开始尝试在生物医学领域应用等离子体技术,并取得一定研究成果.现简述低温常压等离子体技术的原理及其在口腔医疗领域的应用进展.一、等离子体概述1.等离子体形成的原理:将气体加热或置于高频高压电场中,束缚在原子核外的电子被加速获得较大动能,挣脱原子核引力并与分子碰撞而发生电离作用,产生新的自由电子、离子、自由基等,其中的带电粒子被继续加速,再碰撞电离其他分子,该过程循环往复得到的呈电中性并具备高电离度的气体团即为等离子体[2].等离子体按照产生方式可分为自然和实验等离子体,根据气压可分为常压和低压等离子体,根据温度可分为高温和低温等离子体.近年低温常压等离子体(non-thermal atmospheric pressure plasma,NAPP)的发生装置研制成功,这种等离子体在能量转换时对周围环境的加热作用较弱,因此可保持低温(＜40℃),使得等离子体技术可以应用于生物医学领域,为等离子体技术开辟了新的研究方向[3-5]。

Oxidative Stress and Cell Death Induced in U-937 Human Monocytic Cancer Cell Line by Non-Thermal Atmospheric Air Plasma Soft Jet

Oxidative Stress and Cell Death Induced in U-937 Human Monocytic Cancer Cell Line by Non-Thermal Atmospheric Air Plasma Soft Jet

The eco-friendly surface modification of textiles for deep digital textile printing by in-line atmospheric non-thermal plasma treatment

This study evaluated the potential application of an atmospheric plasma (AP) treatment as a pre-treatment for digital textile printing (DTP) of polyester (PET) fabrics and cotton, in order to determine its viability as an alternative to the usual chemical treatment. The surface properties of the AP-treated fabrics were examined through scanning electron microscopy (SEM) and contact angle, and the physical properties, such as electrostatic voltage and water absorbance, were tested. The properties of cotton and PET with the AP treatment were found to be dependent on number of repetitions and electric voltage. Although no remarkable surface differences were observed by SEM in the fabrics before and after treatment, the static contact angle of the PET after AP treatment was decreased from 85 ° to 24 ° at wave. In addition, the charge decay time decreased as the voltage and number of treatments increased. The absorption height of PET changed after exposure to 7 mm with increasing measurement time. The K/S with and without the AP pre-treated and DTP finished cotton was better than that with the usual chemical modification. In PET, the 0.5 kW and 1 time AP-treated specimen showed the highest K/S values.

Acetaldehyde removal using an atmospheric non-thermal plasma combined with a packed bed: Role of the adsorption process

This work is an attempt in order to help towards understanding the influence of the adsorption process on the removal of a VOC (acetaldehyde, CH3CHO) using cyclic non thermal plasma (NTP) combined with a packed-bed of a catalyst support, α-Al2O3. In the first part, the results obtained by placing the saturated alumina pellets inside the plasma discharge zone are discussed, in terms of acetaldehyde removal, CO and CO2 production. In the second part, adsorption of CH3CHO, CO, CO2 and O3 was carried out, from single and multicomponent mixtures of the different compounds. The results showed that (i) the adsorption capacities followed the order CH3CHO ≫ CO2 > CO; (ii) O3 was decomposed on the alumina surface; (iii) CO oxidation occurred on the surface when O3 was present. In the third part, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to follow the alumina surface during acetaldehyde adsorption. DRIFTS measurements demonstrated that besides the bands of molecularly adsorbed acetaldehyde, several absorptions appeared on the spectra showing the intermediate surface transformation of acetaldehyde already at 300K. Finally, the relationship between the adsorption results and the NTP combined with a packed-bed process is discussed.

Antimicrobial effects of non-thermal atmospheric plasma as a novel root canal disinfectant

This study aimed to investigate effects of non-thermal atmospheric plasma on an Enterococcus faecalis biofilm within the canals of extracted human teeth. A significant decrease in the number of CFU׳s was observed after 2min cold plasma treatment with an average kill rate of 99.999%. MTT assay showed a significant reduction in the viability of bacteria with a reduction rate of 98.939%. XTT assay showed a reduction of bacterial metabolic activity by 99.7%. Both 2min cold plasma and 6% NaOCl greatly reduced the viability and metabolic activity of E. faecalis bacteria, but there is no significant difference between them.

Design, Construction and Characterization of AC Atmospheric Pressure Air Non-thermal Plasma Jet

This paper presents the design and construction of non-thermal plasma jet device which was built in plasma phys. Dept., NRC, AEA, Egypt with a plasma application group. This design will be useful to initiate research in different fields such as low temperature plasma, polymer and biomedical applications. The experimental operation of this device is conducted with power supply of (10 kV, 30 mA, and 20 kHz). The discharge process takes place by using Air as input gas with different flow rates. The experimental results showed that the maximum plasma jet length of 7 mm is detected at air flow rate of 12 L/min. The electrical characteristics of discharge at different flow rates of Air such as discharge voltage, current, mean power, power efficiency, and energy have been studied by using potential dividers and Lissajous figure techniques. The results of plasma jet temperature along the jet length showed that the jet plasma has approximately a room temperature at the end of jet column.

Non-thermal atmospheric plasmas in dental restoration: Improved resin adhesive penetration

ObjectiveTo investigate the influence of non-thermal plasma treatment on the penetration of a model dental adhesive into the demineralized dentine. MethodsPrepared dentine surfaces were conditioned with Scotchbond Universal etchant for 15s and sectioned equally perpendicular to the etched surfaces. The separated halves were randomly selected for treatment with an argon plasma brush (input current 6mA, treatment time 30s) or gentle argon air blowing (treatment time 30s, as control). The plasma-treated specimens and control specimens were applied with a model adhesive containing 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]-propane (BisGMA) and 2-hydroxyethyl methacrylate (HEMA) (mass ratio of 30/70), gently air-dried for 5s, and light-cured for 20s. Cross-sectional specimens were characterized using micro-Raman spectral mapping across the dentine, adhesive/dentine interface, and adhesive layer at 1-μm spatial resolution. SEM was also employed to examine the adhesive/dentine interfacial morphology. ResultsThe micro-Raman result disclosed that plasma treatment significantly improved the penetration of the adhesive, evidenced by the apparently higher content of the adhesive at the adhesive/dentine interface as compared to the control. Specifically, the improvement of the adhesive penetration using plasma technique was achieved by dramatically enhancing the penetration of hydrophilic monomer (HEMA), while maintaining the penetration of hydrophobic monomer (BisGMA). Morphological observation at the adhesive/dentine interface using SEM also confirmed the improved adhesive penetration. The results further suggested that plasma treatment could benefit polymerization of the adhesive, especially in the interface region. ConclusionThe significant role of the non-thermal plasma brush in improving the adhesive penetration into demineralized dentine has been demonstrated. The results obtained may offer a better prospect of using plasma in dental restoration to optimize adhesion between tooth substrate and restorative materials.

Reformation of hydrocarbons using non-thermal plasma at atmospheric pressure: discharge characteristics and associated nonlinear dynamics

This paper studies the atmospheric non-thermal plasma generated in a hydrocarbon reforming system. Here, discharge is excited in a typically designed electrode configuration and has been carried out with four different combination pairs of electrodes. The plasma discharge is attained by applying high ac (pulsed) voltages between electrodes. The voltage–current characteristics have been studied in the system with respect to different electrode materials such as steel (SS304), copper and nickel. A Langmuir probe is used to measure fluctuations in the ion saturation region with all electrode configurations. The Hilbert transform technique and empirical mode decomposition have been used to understand the nonlinear dynamics of the fluctuation signals.

Electrical Parameters Investigation and Zero Flow Rate Effect of Nitrogen Atmospheric Nonthermal Plasma Jet

The construction and operation of atmospheric nonthermal plasma jet, ANPJ, are presented in this work as well as the experimental investigations of its electrical parameters, the configuration of plasma jet column and its temperature. The device is energized by a low-cost Neon power supply of (10 kV, 30 mA, and 20 kHz) and the discharge takes place by using N2 gas with different flow rates from 3 to 25 L/min and input voltage of 6 kV. Diagnostic techniques such as voltage divider, Lissajous figure, image processing and thermometer are used. The electrical characteristics of discharge at different flow rates of N2 gas such as discharge voltage, current, mean power, power efficiency, and mean energy have been studied. The experimental results show that the maximum plasma jet length of 14 mm is detected at flow rate of 12 L/min. The results of plasma jet (heavy particles) temperature along the jet length show that jet plasma has approximately a room temperature at the jet column end. The results of zero flow rate effect on the ANPJ operation show damage in the Teflon insulator and a corrosion in the Aluminum electrodes.

The Gas Nucleation Process Study of Anatase TiO2 in Atmospheric Non-Thermal Plasma Enhanced Chemical Vapor Deposition

The gas phase nucleation process of anatase TiO2 in atmospheric non-thermal plasma enhanced chemical vapor deposition is studied. The particles synthesized in the plasma gas phase at different power density were collected outside of the reactor. The structure of the collected particles has been investigated by field scanning electron microscope (FESEM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The analysis shows that uniform crystalline nuclei with average size of several nanometers have been formed in the scale of micro second through this reactive atmospheric plasma gas process. The crystallinity of the nanoparticles increases with power density. The high density of crystalline nanonuclei in the plasma gas phase and the low gas temperature are beneficial to the fast deposition of the 3D porous anatase TiO2 film.

Effects of non-thermal atmospheric pressure air plasma exposure on SLA-treated implant in relation to cellular activity

Surface properties of titanium implants are known as important factors for successful osseointegration. The purpose of this research is to apply recently highlighted non-thermal atmospheric pressure plasma jet (NTAPPJ) on sand blast, large grit, acid etching(SLA) treated Titaniumi surface to improve the hydrophilicity and cellular response. The change in the chemical binding state of SLA-treated Ti before and after the NTAPPJ treatment were determined using field emission scanning electron icroscope, optical surface roughness system, X-ray photoelectron spectroscope, and water contact angle measuring system. MC3T3-E1 cells (murine osteoblastic cell line) attachments and proliferations were examined by the PrestoBlue reagent. This study found that the compressed air-based NTAPPJ treatment on SLA-treated Ti surface significantly increased the hydrophilicity and MC3T3-E1 cell attachments and proliferations. These results suggested that compressed air-based NTAPPJ treatment on the SLA-treated Ti surface had an effect on increasing attachments and proliferations of MC3T3-E1 cell for better osseointegration in

Skeletal Cell Differentiation Is Enhanced by Atmospheric Dielectric Barrier Discharge Plasma Treatment

Enhancing chondrogenic and osteogenic differentiation is of paramount importance in providing effective regenerative therapies and improving the rate of fracture healing. This study investigated the potential of non-thermal atmospheric dielectric barrier discharge plasma (NT-plasma) to enhance chondrocyte and osteoblast proliferation and differentiation. Although the exact mechanism by which NT-plasma interacts with cells is undefined, it is known that during treatment the atmosphere is ionized generating extracellular reactive oxygen and nitrogen species (ROS and RNS) and an electric field. Appropriate NT-plasma conditions were determined using lactate-dehydrogenase release, flow cytometric live/dead assay, flow cytometric cell cycle analysis, and Western blots to evaluate DNA damage and mitochondrial integrity. We observed that specific NT-plasma conditions were required to prevent cell death, and that loss of pre-osteoblastic cell viability was dependent on intracellular ROS and RNS production. To further investigate the involvement of intracellular ROS, fluorescent intracellular dyes Mitosox (superoxide) and dihydrorhodamine (peroxide) were used to assess onset and duration after NT-plasma treatment. Both intracellular superoxide and peroxide were found to increase immediately post NT-plasma treatment. These increases were sustained for one hour but returned to control levels by 24 hr. Using the same treatment conditions, osteogenic differentiation by NT-plasma was assessed and compared to peroxide or osteogenic media containing β-glycerolphosphate. Although both NT-plasma and peroxide induced differentiation-specific gene expression, neither was as effective as the osteogenic media. However, treatment of cells with NT-plasma after 24 hr in osteogenic or chondrogenic media significantly enhanced differentiation as compared to differentiation media alone. The results of this study show that NT-plasma can selectively initiate and amplify ROS signaling to enhance differentiation, and suggest this technology could be used to enhance bone fusion and improve healing after skeletal injury.

NON-THERMAL PLASMA AT ATMOSPHERIC PRESSURE: SYSTEM DESIGN AND DEVELOPMENT

The low-current non-thermal atmospheric plasma source is a useful cost-effective tool for many applications. One of the major applications of this source is to reform hydrocarbons to produce hydrogen. Here, the focus is on the design and development of a system for this process. The system described uses much lower current compared to the other thermal plasma systems and operates at atmospheric pressure eliminating the need for an expensive vacuum system. The system consists of a plasmatron, a fuel injection system for both liquid and gaseous forms, a window for inserting diagnostics systems, and a system to collect output signals from plasma. The non-thermal plasma was produced at high pressure with an AC high-frequency power supply. A three electrode system (copper, stainless steel 314, and nickel) were used with four different configurations. Initial discharge characteristics have been measured for all electrode configurations. The breakdown properties of the system with the electrode configurations and corresponding ionization coefficient (α) have been estimated. A cylindrical Langmuir probe was used to measure and estimate relevant plasma parameters.

Nonthermal Atmospheric Argon Plasma Jet Effects on Escherichia coli Biomacromolecules

Nonthermal atmospheric plasma jet, a promising technology based on ionized gas at low temperatures, can be applied for disinfection of contaminated surfaces. In this study, Escherichia coli cells and their macromolecules were exposed to the nonthermal atmospheric argon plasma jet for different time durations. Total protein, genomic DNA, and malondialdehyde (MDA) levels of E. coli were assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining; agarose gel electrophoresis; and measurement of absorbance at 534 nm, respectively. After exposure, the spectroscopic results of liquid samples indicated that the survival reduction of E. coli can reach to 100 % in an exposure time of 600 s. Moreover, inactivation zones of E. coli, DNA degradation, and MDA levels were significantly increased. Additionally, banding patterns of total protein were changed and amino acid concentrations increased following ninhydrin test. The experimental results suggest that the nonthermal plasma could serve as an effective instrument for both sterilizing E. coli and degrading macromolecules from the surface of the objects being sterilized.