Plasma Jet Treatment Research Articles

Air atmospheric-pressure plasma-jet treatment enhances the attachment of human gingival fibroblasts for early peri-implant soft tissue seals on titanium dental implant abutments

Objective. Although dental implants are commonly used for tooth restoration, there is a lack of studies of treatment regimens for preventing extra-oral infection and decreasing osseointegration failures by establishing early peri-implant soft tissue seals on titanium dental implant abutments. In this study, air atmospheric-pressure plasma-jet (AAPPJ) treatment was applied to titanium disks to assay the potential for early peri-implant soft tissue seals on titanium dental implant abutment. Materials and methods. After titanium disks were treated with AAPPJ for 10 s at 250, 500, 1000 and 1500 sccm, surface analysis was performed; the control group received air only or no treatment. Human gingival fibroblasts (HGF) were seeded onto the specimens for evaluating cell attachment and proliferation and adherent-cell morphology was visualized via confocal microscopy. Results. In AAPPJ-treated specimens, the water contact angle decreased according to increased flow rate. Oxygen composition increased in XPS, but no topographical changes were detected. The effect of AAPPJ treatment at 1000 sccm was apparent 2 mm from the treated spot, with a 20% increase in early cell attachment and proliferation. Adherent HGF on AAPPJ-treated specimens displayed a stretched phenotype with more vinculin formation than the control group. Conclusions. Within the limitations of this study, the results indicate that AAPPJ treatment may enhance the early attachment and proliferation of HGF for establishing early peri-implant soft tissue seals on titanium dental implant abutments with possible favorable effects of osseointegration of dental implant.

Effects of atmospheric pressure plasma JET treatment on aluminium alloys

In this paper, the effect of surface treatments carried out with an atmospheric pressure plasma jet, generated by air, on the passive film of AA1071 and AA2024 was investigated. The samples of the aluminium alloys, before and after the surface plasma treatments, were analysed by secondary ions mass spectrometry depth profiling and by X-ray photoelectron spectroscopy. Potentiodynamic anodic polarisation tests and electrochemical impedance spectroscopy measurements were carried out to study the influence of the surface plasma treatments on the corrosion resistance properties of the Al alloys. The plasma treatments induced the oxidation of the surface and the formation of a thicker and denser passive layer, which exhibited higher corrosion resistance than the native film.

Rapid atmospheric pressure plasma jet processed reduced graphene oxide counter electrodes for dye-sensitized solar cells.

In this work, we present the use of reduced graphene oxide (rGO) as the counter electrode materials in dye-sensitized solar cells (DSSCs). rGO was first deposited on a fluorine-doped tin oxide glass substrate by screen-printing, followed by post-treatment to remove excessive organic additives. We investigated the effect of atmospheric pressure plasma jet (APPJ) treatment on the DSSC performance. A power conversion efficiency of 5.19% was reached when DSSCs with an rGO counter electrode were treated by APPJs in the ambient air for a few seconds. For comparison, it requires a conventional calcination process at 400 °C for 15 min to obtain comparable efficiency. Scanning electron micrographs show that the APPJ treatment modifies the rGO structure, which may reduce its conductivity in part but simultaneously greatly enhances its catalytic activity. Combined with the rapid removal of organic additives by the highly reactive APPJ, DSSCs with APPJ-treated rGO counter electrode show comparable efficiencies to furnace-calcined rGO counter electrodes with greatly reduced process time. This ultrashort process time renders an estimated energy consumption per unit area of 1.1 kJ/cm(2), which is only one-third of that consumed in a conventional furnace calcination process. This new methodology thus saves energy, cost, and time, which is greatly beneficial to future mass production.

Amorphization and Polymorphism Modification of Polyamide-6 Films via Open-Air Non-Equilibrium Atmospheric Pressure Plasma Jet Treatment

Surface activation of polymers by atmospheric pressure plasma is an economically important process for bonding technologies. Although most of the studies are focused on the modification of the surface chemistry, this study investigates the modification of the topmost surface and the deeper layers of a polyamide-6 sheet treated by an open-air atmospheric plasma jet system. The plasma jet used in this study is a unique combination of highly reactive species (e.g. O°, °OH …) and a high temperature gas estimated (from 600–1 000 K) which leads to surface functionalization, amorphization and polymorphism modification. The results have shown that an amorphization of the polyamide occurs on the top surface. Moreover, a crystallization of the amorphous phase in the α form was also highlighted in the depth of the material.

Surface memory effect enhanced by atmospheric pressure plasma jet treatment for liquid crystal alignment

In the present work we tried to study Polyimide (PI) film surface memory effect (SME) enhanced by atmospheric pressure plasma jet (APPJ) treatment for liquid crystal (LC) alignment. To evaluate and describe structural changes on the PI film surface, contact angle measurements and Fourier Transformed Infrared (FTIR) Spectroscopy methods were used. After each treatment cycle, the water drop contact angle to the treated surface decreases and FTIR spectra show an increase of CO bonds. When LCs in mesophase are injected into a cell flow alignment occurs, and SME imprints the LC flow alignment pattern onto the surface. Some materials like glass and PI films naturally have SME to some degree; however, in our work we show that treatment by APPJ leads to the enhancement of this effect. Kinetics of the alignment pattern imprinting process was investigated by varying the incubation duration, and at room temperature the minimum required time for the imprinting alignment pattern was found to be 20min. It was shown that the imprinted alignment of LCs on APPJ treated PI films has excellent heat resistance up to 150°C.

Cell immobilization on polymer by air atmospheric pressure plasma jet treatment

The study of cell immobilization on delicate polymer by an air atmospheric pressure plasma jet (AAPPJ) is required for its medical application. The aim of this study was to evaluate whether AAPPJ treatment induce cell immobilization effect on delicate polymers without significant change of surface roughness by AAPPJ treatment. After surface roughness, dynamic contact angle, and chemical characteristics were investigated, the immobilization effect was evaluated with the mouse fibroblast L929 cell line. Surface roughness change was not observed (P > 0.05) in either delicate dental wax or polystyrene plate (PSP) as advancing and receding contact angles significantly decreased (P < 0.05), thanks to decreased hydrocarbon and formation of oxygen-related functional groups in treated PSP. Adherent L929 cells with elongated morphology were found in treated PSP along with the formation of immobilization markers vinculin and actin cytoskeleton. Increased PTK2 gene expression upregulated these markers on treated PSP.

Electromechanical properties of MgZnO/ZnO heterostructures on flexible polyimide and stainless steel substrates under flexing

We investigate the electromechanical properties of radio frequency (rf)-sputtered MgZnO/ZnO heterostructures on flexible polyimide (PI) and stainless steel 304 (StSt304) substrates. By subjecting ZnO to ultra-short (30–40 s) atmospheric pressure plasma jet treatment and prolonged (>3 h) thermal annealing at 300 °C, highly conductive interfaces are induced in rf-sputtered MgZnO/ZnO heterostructures on flexible PI and StSt304 substrates. The electrical properties of on-StSt MgZnO/ZnO annealed at 400 °C for 30 min are evaluated under the inward and outward bending conditions. Furthermore, the electrical properties of on-PI MgZnO/ZnO heterostructures annealed at 300 °C for 3 h are examined under the bending and stretching conditions. Compared with ZnO, MgZnO/ZnO heterostructures show better electrical stability under mechanical flexing; deviations in the electrical properties of MgZnO/ZnO heterostructures occur under larger strain levels. Piezoelectric polarization is induced under flexing, resulting in an increase or decrease in the resistance of MgZnO/ZnO heterostructures.

A ‘tissue model’ to study the plasma delivery of reactive oxygen species

We demonstrate the utility of a ‘tissue model’ to monitor the delivery of plasma jet-generated reactive oxygen species (ROS). We report on helium plasma jet interactions both across the surface and into the subsurface (defined as 150 µm to 1.5 mm) of the tissue model. The model comprises a gelatin gel encapsulating a homogeneously dispersed chemical or biological reporter molecule. Jet–surface interactions result in (i) star shaped patterns that resemble those previously reported for surface-plasma streamers on insulators (as imaged by Pockels sensing) and (ii) ‘filled’ or hollow circular surface features, which resemble the ‘killing’ patterns seen in plasma jet treatments of bacterial lawns.The use of reporter molecules show that plasma can deliver ROS from 150 µm to 1.5 mm below the tissue surface. Subsurface delivery of ROS is consistent with the use of plasma to decontaminate wounds (covered by wound exudate and clotted blood), the deactivation of whole biofilms, plasma-enhanced drug delivery through skin and the destruction of solid tumours.From the data presented, we argue that in these four cases (and others) ROS may be capable of directly accessing a tissue's subsurface, as opposed to other proposed mechanisms, which involve stimulating surface reactions that trigger a cascade of biomolecular signalling events (into the tissue).

RETRACTED: Safety evaluation of nonthermal atmospheric pressure plasma liquid treatment: Single DNA molecule-based method

We evaluated the beneficial effect of biological decontamination versus the DNA double strand breakage for a range of plasma jet treatment durations. We confirmed the effectiveness of the experimental procedure using a mixture of Escherichia coli and λDNA in buffered solutions. We simultaneously obtained the DNA cutting rate, k, and the decimal reduction value of the viability, D, for safety evaluation of plasma treatment. The results indicate that the toxicity of injected radicals could be quantitatively evaluated by measuring the DNA cutting rate k. In addition, the evaluation could be performed fast without cell cultivation.

Atmospheric pressure plasma jet treatment evokes transient oxidative stress in HaCaT keratinocytes and influences cell physiology

Modern non-thermal atmospheric pressure plasma sources enable controllable interaction with biological systems. Their future applications - e.g. wound management - are based on their unique mixture of reactive components sparking both stimulatory as well as inhibitory processes. To gain detailed understanding of plasma-cell interaction and with respect to risk awareness, key mechanisms need to be identified. This study focuses on the impact of an argon non-thermal atmospheric pressure plasma jet (kINPen 09) on human HaCaT keratinocytes. With increasing duration, cell viability decreased. In accordance, cells accumulated in G2/M phase within the following 24 h. DNA single-strand breaks were detected immediately after treatment and receded in the aftermath, returning to control levels after 24 h. No directly plasma-related DNA double-strand breaks were detected over the same time. Concurrently, DNA synthesis decreased. Coincident with treatment time, an increase in intracellular 2',7'-dichlorodihydrofluorescein diacetate (H(2)DCFDA) conversion increased reactive oxygen species (ROS) levels. The radical scavenging activity of culture medium crucially influenced these effects. Thus, ROS changed DNA integrity, and the effectiveness of cellular defence mechanisms characterises the interaction of non-thermal plasma and eukaryotic cells. Effects were time-dependent, indicating an active response of the eukaryotic cells. Hence, a stimulation of eukaryotic cells using short-term non-thermal plasma treatment seems possible, eg in the context of chronic wound care. Long-term plasma treatments stopped in cell proliferation and apoptosis, which might be relevant in controlling neoplastic conditions.

Cellular membrane collapse by atmospheric-pressure plasma jet

Cellular membrane dysfunction caused by air plasma in cancer cells has been studied to exploit atmospheric-pressure plasma jets for cancer therapy. Here, we report that plasma jet treatment of cervical cancer HeLa cells increased electrical conductivity across the cellular lipid membrane and caused simultaneous lipid oxidation and cellular membrane collapse. We made this finding by employing a self-manufactured microelectrode chip. Furthermore, increased roughness of the cellular lipid membrane and sequential collapse of the membrane were observed by atomic force microscopy following plasma jet treatment. These results suggest that the cellular membrane catastrophe occurs via coincident altered electrical conductivity, lipid oxidation, and membrane roughening caused by an atmospheric-pressure plasma jet, possibly resulting in cellular vulnerability to reactive species generated from the plasma as well as cytotoxicity to cancer cells.

Atmospheric Pressure Plasma Jet in Ar and O2/Ar Mixtures: Properties and High Performance for Surface Cleaning

An atmospheric pressure plasma jet generated in Ar and O2/Ar mixtures has been investigated by specially designed equipment with double power electrodes at 20∼32 kHz, and their effects on the cleaning of surfaces have been studied. Properties of the jet discharge are studied by electrical diagnostics, including the waveform of discharge voltage, discharge current and the Q-V Lissajous figures. The optical emission spectroscopy is used to measure the plasma parameters, such as the excitation temperature and the gas temperature. It is found that the consumed power and the excitation temperature increase with increase of the discharge frequency. On the other hand, at the same discharge frequency, these parameters in O2/Ar mixture plasma are found to be much larger. The effect on surface cleaning is studied from the changes in the contact angle. For Ar plasma jet, the contact angle decreases with increase of the discharge frequency. For O2/Ar mixture plasma jet, the contact angle decreases with increase of discharge frequency up to 26 kHz, however, further increase of discharge frequency does not show further decrease in the contact angle. At the same discharge frequency, the contact angle after O2/Ar mixture plasma cleaning is found to be much lower compared to the case of pure Ar. From the results of quadrupole mass-spectrum analysis, we can identify more fragment molecules of CO and H2O in the emitted gases after O2/Ar plasma jet treatment compared with Ar plasma jet treatment, which are produced by the decomposition of surface organic contaminants during the cleaning process.

Influence of Plasma Treatment on Size Adhesion Strength to Raw Cotton Yarns

This study systematically investigated how helium and oxygen (He/O2) atmospheric pressure plasma jet (APPJ) treatment influences the size adhesion strength (SAS) to the cotton yarn. Results show that the SAS increases with the treatment time from 0 to 18 s then decreases until 24s. The SAS has a decreasing trend when the jet to sample distance (JTSD) goes up from 1.5 to 6.0 mm and it increases with the rising of O2 flux from 0.1 to 0.3 L/min then decreases until 0.45 L/min. For samples with different moisture regains (MRs) of 0.5%, 9.3% and 26.3%, the SAS decreases as the MR rises up. SEM and XPS analyses show that APPJ treated samples have roughened surfaces and are introduced polar bonds such as COH, C=O and OC=O. Cotton fibers with lower MRs are more efficiently etched and more polar bonds are imparted by the APPJ treatment.

Aging of hydrophobized surfaces of ramie fibers induced by atmospheric pressure plasma treatment with ethanol pretreatment

In order to investigate hydrophilic recovery of hydrophobic treatment of cellulose fibers, ramie fibers are ethanol-pretreated followed by atmospheric pressure plasma jet (APPJ) treatment using helium as the treatment gas and age for up to 150 days in 20 °C and 65% relative humidity. Scanning electron microscopy shows the fiber surfaces of the ethanol-pretreated + APPJ-treated group of freshly prepared, aged for 30 days, and aged for 150 days are covered with polypropylene matrix after fiber pullout tests. X-ray photoelectron spectroscopy shows that the freshly prepared ethanol-pretreated + APPJ-treated group has a 31% reduction in atomic ratio of oxygen to carbon and maintains at a similar level even after 150 days of aging. Water contact angle measurement demonstrates that the wettability of fiber surface of the freshly prepared ethanol-pretreated + APPJ-treated group drastically decreases and remains at the same lever after aging. Interfacial shear strength test reveals that the interfacial adhesion between PP matrix and ramie fiber for the freshly prepared ethanol-pretreated + APPJ-treated group increases 26% and remains substantially higher than that of the control group over time. These results indicate that the ethanol pretreatment followed by APPJ treatment is a permanent surface treatment with negligible aging for at least five months.

Antibacterial plasma at safe levels for skin cells

Plasmas produce various reactive species, which are known to be very effective in killing bacteria. Plasma conditions, at which efficient bacterial inactivation is observed, are often not compatible with leaving human cells unharmed. The purpose of this study was to determine plasma settings for inactivation of Pseudomonas aeruginosa, without damaging skin cells in vitro under the same treatment conditions. An RF argon plasma jet excited with either continuous or time modulated (20 kHz, 20% duty cycle) voltages was used. To compare these two operation modes, only the input voltage was adjusted in order to obtain the same average power (1.7 W) for both modes. All other settings, i.e. gas flow, distance plasma tip to liquid surface, were kept constant. Bacteria or skin cells in physiological salt solution were exposed to direct non-contact plasma treatments. Short plasma treatments of up to 2 min resulted in a high reduction of bacterial numbers and did not affect dermal fibroblasts or keratinocytes. Bacterial inactivation has been previously ascribed to peroxynitrite, nitrite and H2O2 while eukaryotic cell viability is proposed to be reduced in the long term by the presence of H2O2 and is less affected by reactive nitrogen species. The remote RF plasma jet treatment was highly effective for bacterial inactivation while skin cell viability was preserved.

코로나방전플라즈마제트장치의 조업특성과 살균력

A corona discharge plasma jet (CDPJ) treatment system was fabricated and its operation characteristics were determined. Also the microbial inactivation efficacy of CDPJ was evaluated in order to explore its potentialities as a nonthermal sterilization technology. The system consisted of power supply, transformer, electrode assembly, air blower, and sample treatment plate. Plasma was generated by corona discharge between tungsten lid electrodes with air stream blowing at high speed resulting in downward plasma ejection as a jet. Higher currents and, consequently, greater power were required for the plasma generation as the frequencies increased. Plasmas were generated at a current greater than 1.0 A and frequencies over 32.5 kHz. Stable plasma jets were acquired when the current and the frequency exceeded 1.5 A and 40.0 kHz. Plasma jet length was extended with the current strength. The maximum temperature increased after a 2 min treatment was less than 25oC regardless of the current strength, indicating that the technology belonged to the non-thermal processing category. The CDPJ inactivation effect against Escherichia coli increased with the current strength. More than 4.5 log reduction was achieved by 1 min treatment at 1.5 A. The inactivation pattern fitted to a 2-stage 1st order reaction model.

Surface Treatment of Polyethylene Terephthalate to Improving Hydrophilicity Using Atmospheric Pressure Plasma Jet

In this paper, the effects of atmospheric pressure argon (Ar) plasma jet treatments on the surface properties of polyethylene terephthalate films are studied. Different discharge power density, treatment distance, and treatment time are selected to study the effects of discharge operation parameters on the surface treatments, and the surface properties of the untreated and plasma-treated samples are characterized through water contact angle and surface energy measurement, Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy, with the modification mechanism being discussed. Results show that after the atmospheric pressure Ar plasma jet treatment, the water contact angle decreases with the increase of treatment time and surface energy increases with the increase of treatment time, and both of them reach saturated value at certain treatment time. It is found that, the shorter the treatment distance and the higher discharge power density are, the greater are the water contact angle decreasing and surface energy increasing, and the introduction of oxygen-containing polar groups is the main reason for the improvement of surface hydrophilicity. Therefore by shorting treatment distance and increasing the discharge power density, more oxygen-containing polar groups are generated in the jet, thus the treatment time to obtain the efficient treatment effect is reduced.

Steam Plasma Jet Treatment of Phenol in Aqueous Solution at Atmospheric Pressure

AbstractSteam plasma jet (SPJ) was generated by phenol aqueous solution introduced into water plasma torch as plasma forming gas, which injected into phenol aqueous solution to conduct oxidation degradation of organic pollutants in aqueous solutions. The experimental results indicated that the phenol was not only decomposed in SPJ, but also degraded in phenol aqueous solution due to high concentration hydroxyl radicals. Moreover, the energy efficiencies significantly increased from (1.6–1.8) × 10−10 to (4.8–8.0) × 10−8 mol · J−1 with the initial concentration of phenol increased from 0.5 to 50.0 g · L−1. The main intermediates of phenol decomposition were pyrocatechol, hydroquinone, maleic acid, butanedioic acid, and muconic acid in liquid. The major gaseous effluence products were H2, CO, and CO2. magnified image

The effects of non-thermal atmospheric pressure plasma jet on cellular activity at SLA-treated titanium surfaces

Titanium (Ti) is a primary material used for dental implants, and the sandblasted, large-grit, and acid-etched (SLA) surface treatment is commonly used on titanium to promote early osseointegration. Despite their benefits, SLA-treated Ti surfaces are disadvantaged by their hydrophobic property, and much research has been performed to address this problem. In current study, we hypothesized the effects of a nitrogen-based non-thermal atmospheric pressure plasma jet (NTAPPJ) treatment on SLA-treated Ti would increase hydrophilicity and cellular activity. Samples with and without the NTAPPJ treatment were analyzed using a field emission scanning electron microscope, 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 MTT and BrdU colorimetry assay. Cell immunofluorescent microscopic images were observed by a confocal laser scanning microscope for a morphological analysis. This study found that the nitrogen-based NTAPPJ treatment on SLA-treated Ti significantly increased the hydrophilicity and MC3T3-E1 cell attachments and proliferations. Hence, it was concluded that an additional procedure of nitrogen-based NTAPPJ treatment just prior to implantation of SLA-treated Ti into oral defect sites could improve the success of dental implant surgery.

Modification of Enamel and Dentin Surfaces by Non‐Thermal Atmospheric Plasma

AbstractTooth material surface chemical and micromechanical properties are important for success and sustainability in restorative dentistry. Modification by cold atmospheric plasma jet treatment may help to improve presently existing shortcomings as a part of future restorative therapies. The present study has been focused on changes of surface properties of tooth substances by this approach. Polished and etched enamel and dentin slices from the vestibular face of bovine incisors are used. A plasma jet modifies these surfaces at a distance of 2 mm and with a scan velocity of 5.5 mm · s−1. The treatment parameters are: helium process gas flow 3.525 slm, plasma excitation by 2.45 GHz with an average pulsed microwave power of 2 W, single pulse power of 250 W, pulse width 5 µs. The surface modifications are subjected to laser scanning microscope roughness‐measurement, contact angle measurements, X‐ray photoelectron spectroscopy (XPS) analysis and morphological visualization by scanning electron microscopy (SEM). Plasma treatment causes changes of surface roughness and morphological alterations on dentin, while no such changes are measureable on etched dentin and polished and etched enamel surfaces. Plasma causes contact angle reductions for both, water and ethylene glycol. XPS analyses show significant carbon reduction on enamel surfaces after plasma treatment. Admixture of 30% of hydrogen peroxide or deionized water, respectively, as precursors in the plasma jet processing gas flow generates measureable amounts of CO‐bindings at the surfaces assigned to hydrophilic groups. Surface modifications by plasma treatment might enable interesting new options for dental procedures in all areas of interaction between tooth substance and restorative materials. magnified image