Atmospheric Pressure Plasma Jet Treatment Research Articles

Mass Spectrometry Analysis of the Real-Time Transport of Plasma-Generated Ionic Species Through an Agarose Tissue Model Target

With ambient mass spectrometry, we followed the transport of neutral gas species and ionic species through a 3.2 mm thick agarose tissue model target during He non-thermal atmospheric pressure plasma (NT-APP) jet treatment. We found that the neutral gas species are unable to efficiently penetrate the agarose target. But both positively and negatively charged ionic species readily penetrate through the agarose target, following an initial time-lag period of several minutes. Interestingly, we also found that the ionic species are easily hydrated. The trends in the He NT-APP jet transport of ionic species observed in this study correlate well with the He NT-APP jet transport of reactive oxygen and nitrogen species (RONS) through agarose tissue model targets that was investigated in previous studies. Therefore, mass spectrometry might prove to be a useful tool in the future for analyzing the dosages of NT-APP-generated RONS in real biological tissues.

Generation of biocompatible TiO2 layer using atmospheric pressure plasma-assisted fine particle peening

The effect of atmospheric-pressure plasma jet treatment in conjunction with fine particle peening (FPP) on the generation of a TiO2 layer on pure titanium was investigated. Compared with the TiO2 layer generated using conventional FPP, the layer generated using plasma-assisted FPP was observed to have a uniform and thick surface. Scratch and friction wear evaluation test results revealed that the layer generated with plasma assistance exhibited superior abrasion resistance. These advantages are attributed to the promotion of adhesion of each particle during the plasma treatment. In addition, the layer generated with plasma assistance exhibited superior biocompatibility.

Surface Treatment of Human Hard Dental Tissues with Atmospheric Pressure Plasma Jet

Surface of human hard dental tissues (enamel and dentine) was treated using a helium single-electrode atmospheric pressure plasma jet (APPJ) with the aim of enhancing surface properties of treated material. Modification of the enamel and dentine surface was observed using contact angle measurements and X-ray photoelectron spectroscopy. Even a short treatment time (≈1 s) lead to a significant reduction in the contact angle: 45% for the dentine and 32% for the enamel. After the treatment, the water contact angle tends to return to original (untreated) value and it is shown that stability of wetting strongly depends on the duration of treatment. The surface of the untreated teeth samples consisted mostly of the elements C, O, N, Ca and P. Their relative concentrations changed during 9-min He APPJ treatment. Significant decrease of C and N relative concentrations suggested the removal of adsorbed carbon and nitrogen species and disclosure of underlying inorganic hydroxyapatite structure. The Ca/P ratio has increased from 1.26 to 1.72, which is very close to an ideal ratio for the highest volume of remineralisation of the human dental enamel. Oxidation of the transparent organic matrix in the enamel, one of the major processes in tooth bleaching, was confirmed with the increase of O concentration, from about 31 to 46 at.%. Helium APPJ treatment therefore proved to be a potential tool for chemical surface modification of hard human dental tissues.

In vitro bactericidal efficacy of atmospheric-pressure plasma jet on titanium-based implant infected with Staphylococcus aureus

Staphylococcus aureus is a representative of gram-positive bacteria that causes skin infection, respiratory diseases, and burned tissue infections. The aim of this study was to evaluate the sterilizing efficiency of an atmospheric-pressure plasma jet (APPJ) on S. aureus adhered on a titanium surface. During the APPJ sterilization, the plasma gases used were Ar, Ar+N2, and Ar+O2. With increasing APPJ treatment time, the viability of S. aureus decreased. The addition of O2 gas to Ar gas resulted in a higher sterilizing efficiency than the addition of other groups. Plasma exposure induced bacterial oxidative stress, and it was confirmed that the cell membrane was seriously damaged by the production of reactive oxygen species. Our finding suggests that the APPJ is an effective tool for clinical antimicrobial therapy.

Feasibility study of surface-modified carbon cloth electrodes using atmospheric pressure plasma jets for microbial fuel cells

Abstract This study investigated the surface and electrochemical properties of carbon cloth electrodes surface-modified by using atmospheric pressure plasma jets (APPJs) for applications involving microbial fuel cells (MFCs). APPJ treatment made the carbon cloth highly hydrophilic and did not introduce any observable cracks or flaws. MFCs configured with APPJ-treated carbon cloth electrodes exhibited electrochemical performance (maximum power density of 7.56 mW m −2 ) superior to that of MFCs configured with untreated carbon cloth electrodes (maximum power density of 2.38 mW m −2 ). This boost in performance can be attributed to the formation of abundant carboxyl and ammonium functional groups on the surface of APPJ-treated carbon cloth, which promoted the formation of anodic biofilms and the adhesion of bacteria, while facilitating the transfer of electrons from the bacteria to the electrodes. APPJ surface modification is non-toxic and environmentally friendly (no exogenous chemicals are required), which is particularly beneficial as the introduction of toxins might otherwise inhibit bacterial growth and metabolism. The APPJ surface modification process is rapid, cost-effective, and applicable to substrates covering a large area, making it ideal for the fabrication of large-scale MFCs and bioelectrochemical bioenergy devices.

Atmospheric pressure plasma treatment study for 2-((4-Hydroxyphenyl)Diazenil)Benzene-1,3,5-Triol molecule

In this study, the structural and computational spectroscopic investigations of 2-((4-Hydroxyphenyl)Diazenil)Benzene-1,3,5-Triol molecule (abbreviated as to be 2ABT) were realized. This is AZO dye molecule. The optimized geometric parameters, conformational equilibria, normal mode frequency and corresponding vibrational assignments of 2ABT molecule were examined by means of B3LYP hybrid density function theory (DFT) method together with 6-31G(d) basis set. Computed wavenumbers and intensities were compared with FT-IR spectra of 2ABT molecule in the range of 4000–400cm−1 in solid phase. The thermodynamic parameters have also been computed. The computed frequencies were carried out for different conformations of 2ABT molecule in gas phase. In compliance with the computed results, the vibrational wavenumbers and excitation energies demonstrated a very good agreement with the experimental data. FT-IR spectra of 2ABT molecule decomposing in ethanol and methanol solvents under atmospheric pressure plasma treatment (APPT) with dielectric electrode in liquid phase were also obtained. The atmospheric pressure non-equilibrium plasma jet of argon (Ar) has been formed by ac-power supply. The characterizations of 2ABT molecule in liquid phase have been analysed after (duration: 3min) the atmospheric pressure plasma jet treatment (APPT). We present a new decomposing, decoration and elimination method for chemical of molecules. The different and novel chemical molecules for drug, industry and environmental process can be produced with APPT. APPT was specially designed for the decomposing of the 2ABT molecule for the first time. After the APPT treatment, chemical bonds types were changed. Especially, the molecular bridge of the 2ABT was seriously affected. Few two-photo products were obtained after the APPT. Finally, the new photoproducts can be defined as 9C8N7N6C at 1455.9cm−1 and 3C15O at 1624.84cm−1 stretching peaks.

The effects of humidity on the surface modification of wool fabric through atmospheric pressure plasma jet

Current research was carried out on hydrophilic wool fibers at three different humidity conditions through atmospheric pressure plasma jet (APPJ). Samples were taken to evaluate surface microscopic morphology, surface roughness, directional friction effect (DFE), and surface chemical composition. The scanning electron microscope (SEM) and fiber friction coefficient test (FFT) results show that wetting pretreatment has significant effect on surface etching and DFE, but very limited effect on surface roughness. Allworden reaction and X-ray photoelectron spectroscopy (XPS) results reveal that extra moisture changes C, O, N, S contents and their related characteristic functional groups, therefore increases etching degree on wool fiber surface scales. It was concluded that APPJ treatment is effective in processing wool fiber with high moisture contents.

Metallization and APPJ treatment of bismaleimide

Bismaleimide (BMI) resins are a new breed of thermosetting resins used mainly for high-temperature applications and have major usage in aerospace. Fourier transform infrared (FTIR) studies have shown signatures of imide, C–N–C stretching, maleimide, and N–H stretching. These BMI polymer coatings were deposited on aluminum (Al) and mild steel substrates by sprinkling powers followed by baking. Thermogravimetric analysis and differential scanning calorimetric studies showed the degradation temperature of these polymers around 370°C. Al coatings were deposited on BMI that is previously deposited on Al and mild steel to make a metal–BMI–metal trilayer. These trilayers can solve the problem charging of the aircraft bodies at high altitudes. Atomic force microscopy was done to determine the morphology of the surface. Roughness and thickness measurements of the BMI coatings were carried out by a surface profilometer. Vickers microhardness tests showed an increase in the hardness of the metal–BMI–metal trilayer. FTIR spectrum showed signatures of imides, C–N–C stretching, maleimide, and N–H stretching in BMI. Peak broadening indicates the release of the stress during thermal treatment of the coating. The coating is subject to variable Atmospheric Pressure Plasma Jet (APPJ) conditions, which improves the properties at high temperature. X-ray diffraction studies showed a hint of crystallinity on APPJ treatment.

Atmospheric pressure plasma jet inactivation of Pseudomonas aeruginosa biofilms on stainless steel surfaces

Abstract This study established the efficacy of atmospheric pressure plasma jet on Pseudomonas aeruginosa on stainless steel types 316 and 304; with different finishes namely, mirror (MR), hairline (HL) and 2B surfaces. A cocktail of four strains of P. aeruginosa in the mid-stationary growth phase were allowed to attach on the test surfaces, and subjected to atmospheric pressure plasma jet treatment with an air injection rate of 5 l/min, output power of 360 W at 4.22 cm source-to-surface distance. Attachment rates were significantly affected by surface finish, rather than by stainless steel type. The D-values on the 316 stainless steel type ranged from 2.53 s (MR) to 3.16 s (2B); while those on the 304 type ranged from 1.95 s (HL) to 3.27 s (2B). Variations in D-values were observed between surface finishes within a specific stainless steel type. However, significant variations were not observed between the same surface finish of different steel types. The observed antimicrobial efficacy was attributed to the generation of reactive oxygen species, ultraviolet-C rays, and rapid temperature increase (final temperature of 143.42 °C to 174.05 °C) within 15 s of treatment. In the absence of heating, the D-value increased to 16.45 s, but a 5-log (99.999%) reduction in the population was observed in a relatively short treatment time of 90 s. Industrial relevance The results obtained in this work demonstrated the potential of using atmospheric pressure plasma jet technology as a non-chemical, non-thermal, and thermal stainless steel food contact surface decontamination against Pseudomonas aeruginosa, a common biofilm-producing bacterium. Such a technology shall help the industry address the challenge of cross contamination in the food manufacturing and food service settings.

Contamination control of polymer films by two atmospheric pressure plasma jet treatments

To control contamination resistance of polymer surfaces, the surface hydrophobization and hydrophilization were attempted by atmospheric pressure plasma jet (APPJ)-coating with hexamethyldisiloxane (HMDSO) and APPJ-oxidation, respectively. The APPJ-coating remarkably prevented the deposition of the particulate contaminants in air. The granular morphology was observed on the film surfaces after the APPJ-coating, which resulted in superior contamination resistance via the decrease in the contact area with the contaminant. On the other hand, the APPJ-oxidation promoted the contamination removal in the aqueous detergent system.

Reference organism selection for microwave atmospheric pressure plasma jet treatment of young coconut liquid endosperm

This study identified a reference organism for the establishment of microwave atmospheric pressure plasma jet treatment of young coconut liquid endosperm. Three different, predominant spoilage bacteria were isolated from spoiled liquid endosperm and identified through 16S rDNA sequencing, prior to propagation and eventual challenge studies. Basic Local Alignment Search Tool comparisons revealed that the isolated spoilage bacteria were Klebsiella sp., Staphylococcus sp., and Kluyvera sp (%Identity 97.34–97.82%). The isolates were propagated to mid-stationary growth phase (17 h) and thereafter suspended in liquid endosperm. The inactivation rates of the spoilage isolates in liquid endosperm subjected to plasma jet at 450 and 650 W input power settings were determined and compared to those of pathogens Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes. Inactivation rates of all test organisms at 450 W (2.76–5.98 min) were significantly less (p < 0.05) than those at 650 W (1.86–3.11 min). In both power settings, S. enterica exhibited the significantly (p < 0.05) greatest resistance towards plasma treatment, while Staphylococcus sp. exhibited the least. Heat penetration studies in both power settings revealed that the temperature of the liquid endosperm did not significantly increase and did not reach bactericidal ranges (<30 °C) during plasma jet treatment, hence the observed inactivation were attributed to antimicrobial species generated by the plasma. Optical emission spectroscopy revealed that these antimicrobial species included atomic oxygen (777.41 and 844.67 nm) and ultraviolet radiation (200–280 nm). Thus, this study determined S. enterica as an appropriate target organism for the establishment of plasma jet process for coconut liquid endosperm, the inactivation rate of which shall be soon established in higher scale treatment process.

Functionalization of graphene by atmospheric pressure plasma jet in air or H2O2 environments

The functionalization of graphene, which deforms its band structure, can result in a metal-semiconductor transition. In this work, we report a facile strategy to oxidize single-layer graphene using an atmospheric pressure plasma jet (APPJ) that generates a variety of reactive plasma species at close to ambient temperature. We systematically characterized the oxygen content and chemical structure of the graphene films after plasma treatment under different oxidative conditions (ambient air atmosphere or hydrogen peroxide solution) by X-ray Photoelectron Spectroscopy (XPS). Plasma-treated graphene films containing more than 40% oxygen were obtained in both oxidative environments. Interestingly, prolonged irradiation led to the reduction of graphene oxides. N-doping of graphene also occurred during the APPJ treatment in H2O2 solution; the nitrogen content of the doped graphene was dependent on the duration of irradiation and reached up to 8.1% within 40min. Moreover, the H2O2 solution served as a buffer layer that prevented damage to the graphene during plasma irradiation. Four-point probe measurement revealed an increase in sheet resistance of the plasma-treated graphene, indicating the transition of the material property from semi-metallic to semiconducting.

Effect of non-thermal air atmospheric pressure plasma jet treatment on gingival wound healing

Non-thermal atmospheric pressure plasmas have been applied in the biomedical field for the improvement of various cellular activities. In dentistry, the healing of gingival soft tissue plays an important role in health and aesthetic outcomes. While the biomedical application of plasma has been thoroughly studied in dentistry, a detailed investigation of plasma-mediated human gingival fibroblast (HGF) migration for wound healing and its underlying biological mechanism is still pending. Therefore, the aim of this study is to apply a non-thermal air atmospheric pressure plasma jet (NTAAPPJ) to HGF to measure the migration and to reveal the underlying biological mechanisms involved in the migration. After the characterization of NTAAPPJ by optical emission spectroscopy, the adherent HGF was treated with NTAAPPJ or air with a different flow rate. Cell viability, lipid peroxidation, migration, intracellular reactive oxygen species (ROS), and the expression of migration-related genes (EGFR, PAK1, and MAPK3) were investigated. The level of statistical significance was set at 0.05. NTAAPPJ and air treatment with a flow rate of 250–1000 standard cubic centimetres per minute (sccm) for up to 30 s did not induce significant decreases in cell viability or membrane damage. A significant increase in the migration of mitomycin C-treated HGF was observed after 30 s of NTAAPPJ treatment compared to 30 s air-only treatment, which was induced by high levels of intracellular reactive oxygen species (ROS). An increase in migration-related gene expression and EGFR activation was observed following NTAAPPJ treatment in an air flow rate-dependent manner. This is the first report that NTAAPPJ treatment induces an increase in HGF migration without changing cell viability or causing membrane damage. HGF migration was related to an increase in intracellular ROS, changes in the expression of three of the migration-related genes (EGFR, PAK1, and MAPK1), and EGFR activation. Therefore, NTAAPPJ for gingival tissue healing is a promising method for health and aesthetic outcomes.

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

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

Surface Treatment of Polydimethylsiloxane (PDMS) with Atmospheric Pressure Rotating Plasma Jet. Modeling and Optimization of the Surface Treatment Conditions

Surface treatment of polydimethylsiloxane (PDMS) with a rotative nozzle atmospheric pressure plasma jet (APPJ) was reported. Operating conditions were optimized by statistical design of experiments, using water contact angle and XPS as response variables; OES (optical emission spectroscopy) was used for plasma diagnosis. The nozzle‐PDMS distance and the torch speed were the most influencing parameters and were optimum at 6.6 mm and 10.3 m s−1, respectively. The extent of hydrophobic recovery of treated PDMS, investigated by water contact angle measurements, was less than what reported in the literature for this amorphous polymer. However, the APPJ treatment proposed in this paper is meant to be inserted in line for a homogeneous surface treatment of PDMS for enhanced adhesion improvement to coatings or adhesives.

He/O2 Atmospheric Pressure Plasma Jet Treatments of PCL Scaffolds for Tissue Engineering and Regenerative Medicine

The goal of this work was to achieve proper chemical modification of poly‐ϵ‐caprolactone porous scaffolds by means of He/O2 Atmospheric Pressure Plasma‐Jet treatments with the aim of improving their affinity with cells. The surface chemical composition and wettability of plasma processed scaffolds was characterized, their cyto‐compatibility was tested with human Saos‐2 osteoblasts cells. Plasma‐grafted polar groups were found to improve the hydrophilicity of the scaffolds, which resulted in better clusterization and cytoskeleton morphology of cells cultured on them.

Inactivation of murine norovirus-1 and hepatitis A virus on fresh meats by atmospheric pressure plasma jets

In the current study, inactivation effect of atmospheric pressure plasma (APP) jets (10s–20min) was investigated against murine norovirus (MNV-1), as a norovirus (NoV) surrogate and hepatitis A virus (HAV) associated with three types of fresh meats (beef loin, pork shoulder and chicken breast). The quality characteristics of fresh meats, such as surface color, moisture content and thiobarbituric acid reactive substance (TBARS) were also examined. After 5–20min of treatment with APP jets, the reduction in MNV-1 titers (initial inoculums of 107 plaque-forming units (PFU)) were >2log10PFU/mL in the three types of meat. After 5–20min treatment with APP jets, the reduction in HAV titers (initial inoculums of 106PFU) were >1log10PFU/mL in the three types of meat. There was no significant difference (p>0.05) in the L*, a*, and b* values for APP jet treatment times below 5min. Furthermore, there was no significant difference (p>0.05) in the water content (%) value for treatment times under 5min. Although the TBARS values gradually increased with increase in APP jet treatment times, these TBA values were below 1.0mgMA/kg (an indicator of meat rancidity). The results of the current study indicate that 5min of APP jet treatment showed >99% reduction (2log10PFU/mL) of MNV-1 titer and >90% reduction (1log10PFU/mL) of HAV titer without concomitant changes in meat quality; thus, this procedure can be considered in fresh meat production, processing and distribution processes to enhance fresh meat safety.

Polystyrene as a model system to probe the impact of ambient gas chemistry on polymer surface modifications using remote atmospheric pressure plasma under well-controlled conditions.

An atmospheric pressure plasma jet (APPJ) was used to treat polystyrene (PS) films under remote conditions where neither the plume nor visible afterglow interacts with the film surface. Carefully controlled conditions were achieved by mounting the APPJ inside a vacuum chamber interfaced to a UHV surface analysis system. PS was chosen as a model system as it contains neither oxygen nor nitrogen, has been extensively studied, and provides insight into how the aromatic structures widespread in biological systems are modified by atmospheric plasma. These remote treatments cause negligible etching and surface roughening, which is promising for treatment of sensitive materials. The surface chemistry was measured by X-ray photoelectron spectroscopy to evaluate how ambient chemistry, feed gas chemistry, and plasma-ambient interaction impact the formation of specific moieties. A variety of oxidized carbon species and low concentrations of NOx species were measured after APPJ treatment. In the remote conditions used in this work, modifications are not attributed to short-lived species, e.g., O atoms. It was found that O3 does not correlate with modifications, suggesting that other long-lived species such as singlet delta oxygen or NOx are important. Indeed, surface-bound NO3 was observed after treatment, which must originate from gas phase NOx as neither N nor O are found in the pristine film. By varying the ambient and feed gas chemistry to produce O-rich and O-poor conditions, a possible correlation between the oxygen and nitrogen composition was established. When oxygen is present in the feed gas or ambient, high levels of oxidation with low concentrations of NO3 on the surface were observed. For O-poor conditions, NO and NO2 were measured, suggesting that these species contribute to the oxidation process, but are easily oxidized when oxygen is present. That is, surface oxidation limits and competes with surface nitridation. Overall, surface oxidation takes place easily, but nitridation only occurs under specific conditions with the overall nitrogen content never exceeding 3%. Possible mechanisms for these processes are discussed. This work demonstrates the need to control plasma-ambient interactions and indicates a potential to take advantage of plasma-ambient interactions to fine-tune the reactive species output of APP sources, which is required for specialized applications, including polymer surface modifications and plasma medicine.

Atmospheric-pressure plasma treatment of polyamide 6 composites for bonding with polyurethane

An atmospheric-pressure plasma jet (APPJ)-based surface treatment process was investigated for the structural (τB > 15 MPa) adhesive bonding of polyamide 6 (PA6) composites. The treated surfaces were examined by contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM). Additionally, the shear strengths of single lap specimens were determined as a function of different plasma intensities and polyurethane adhesives. Our results show that APPJ leads to an increase of the surface free energy, oxygen concentration, and number of functional groups. Furthermore, the topography of the surface was significantly modified by exposure to APPJ. AFM measurements show that special attention has to be paid to the intensity of the plasma treatment to avoid melting and flattening of the PA6 surface on the nanometer scale. With optimized multiple APPJ treatments, lap shear strength of 20 MPa was achieved for the first time for this material system, allowing the material system to be employed in future automobile applications.

Investigating effects of atmospheric-pressure plasma on the process of wound healing.

Cold atmospheric-pressure plasma jets (APPJ) have excellent applications in biomedicine. Advantages of APPJ include lack of need for vacuum systems, capability of operation for a long time, and safe to be directly touched by living tissues such as a human body. In this study, an APPJ was generated by a dielectric barrier and applied for the treatment of chemical wounds. This APPJ worked with argon and was driven by high-voltage pulses. This paper compares the spontaneous healing of wounds and a stimulated healing using daily APPJ treatment. Biological data, such as hematological, biochemical, and histological parameters, were remarked. The mortality and morbidity of the untreated samples were reported after 20 days in comparison with the plasma-treated samples, which were alive after these days. Experimental results demonstrated that an increase in the oxidative stress could result in the decreased destruction of lesions by controlling the infection growth. These results were related to the presence of reactive oxygen species and reactive nitrogen species in the plasma volume, which were detected by optical emission spectroscopy.