Low-temperature Atmospheric Plasma Research Articles

Generation of low-temperature plasma by pulse-width modulated signals and monitoring of the interaction thereof with the surface of objects

Abstract The article discusses the use of pulse-width modulation signals to generate low-temperature at-mospheric plasma in an inert gas environment. The results of studies of the energy consumption of a low-temperature plasma generation system depending on the duty rate, as well as the pulse repetition rate, are presented. The operating modes of the system have been established, in which a minimum of energy consumption is achieved. The issues of evaluating the interaction of plasma with objects based on the analysis of changes in signal parameters in the high-voltage circuit of the generator are also considered.

Multimodal intelligent approach to low-temperature atmospheric plasma processing of apple slices before drying.

This study presents a comprehensive analysis of the impact of plasma treatment on the browning inhibition. A 30 min plasma treatment resulted in a pronounced decrease in the concentration of flavan-3-ols, which play a pivotal role in antioxidant defense and browning prevention. This significant reduction is likely due to plasma-induced oxidative stress, which can lead to the breakdown of these compounds or their conversion into other phenolic structures. Simultaneously, a slight increase in dihydrochalcones and flavonols was observed, suggesting a selective effect of plasma on different phenolic classes. The increase in these compounds could be attributed to the plasma's ability to induce specific reactions that generate these phenolics from other precursors present in the apples. The reduction in flavan-3-ols may affect the antioxidant capacity and health benefits associated with the apples, while the increase in dihydrochalcones and flavonols could have a positive impact on the flavor profile and potential health-promoting properties. Moreover, these modifications could contribute to the extension of shelf-life and maintenance of sensory qualities, making plasma treatment a valuable tool in the food industry for enhancing product stability and consumer appeal.

Deposition of a polymer thin film on a silver surface for surface plasmon sensing

We report a deposition method of a polymer thin film on the silver surface of a surface plasmon sensor for preventing sensitivity degradation in refractive index measurements due to the poor chemical stability of the silver. The deposition of a poly(methyl methacrylate) thin film with a ∼15 nm thickness was conducted by employing a spin coating technique along with a hydrophilicity enhancement of the silver surface using an atmospheric low-temperature plasma treatment. We experimentally verified the thickness by measuring the propagation constant of the surface plasmon. The measured propagation constants that showed the standard deviation at the order of 10−4 indicated microscopical uniformity. Furthermore, the reproducibility of thickness was experimentally verified.

Effects of the application of low-temperature atmospheric plasma on titanium implants on wound healing in peri-implant connective tissue in rats

PurposeThis study aimed to clarify the effects of surface modification of titanium (Ti) implants by low-temperature atmospheric pressure plasma treatment on wound healing and cell attachment for biological sealing in peri-implant soft tissue.MethodsHydrophilization to a Ti disk using a handheld low-temperature atmospheric pressure plasma device was evaluated by a contact angle test and compared with an untreated group. In in vivo experiments, plasma-treated pure Ti implants using a handheld plasma device (experimental group: PL) and untreated implants (control group: Cont) were placed into the rat upper molar socket, and samples were harvested at 3, 7 and 14 days after surgery. Histological evaluation was performed to assess biological sealing, collagen- and cell adhesion-related gene expression by reverse transcription quantitative polymerase chain reaction, collagen fiber detection by Picrosirius Red staining, and immunohistochemistry for integrins.ResultsIn in vivo experiments, increased width of the peri-implant connective tissue (PICT) and suppression of epithelial down growth was observed in PL compared with Cont. In addition, high gene expression of types I and XII collagen at 7 days and acceleration of collagen maturation was recognized in PL. Strong immunoreaction of integrin α2, α5, and β1 was observed at the implant contact area of PICT in PL.ConclusionsThe handheld low-temperature atmospheric pressure plasma device provided hydrophilicity on the Ti surface and maintained the width of the contact area of PICT to the implant surface as a result of accelerated collagen maturation and fibroblast adhesion, compared to no plasma application.

Low-Temperature Atmospheric Pressure Plasma Jets and their Applications in the Surface Activation of some Polymeric Substrates for Advanced Electronic Packaging

The present study applied low-temperature atmospheric plasma (LTAPP) jets to modify polymer substrates used in chip packaging. These substrates include bismaleimide triazine (BT), polyimide (PI) and PTFE materials. All these materials play important roles in modern semiconductor packaging. During the study, focuses were aimed the effects of reactive species (mainly OH and atomic oxygen) generated by atmospheric plasma jets on surface energy, water contact angle (WCA) and surface composition of these three substrates. In order to better understand and apply LTAPP jets, another focus will be on the understanding of the relationship among (1) the generation and distribution of various reactive species, (2) parameters for generating LTAPP jet, and (3) plasma characteristics. The plasma activation mechanism of these substrates was also discussed. In addition to plasma generation using AC high-voltage supplies, plasma characterization using optical emission spectroscopy (i.e., analysis of electron density, electron temperature, plasma temperature, and reactive species), XPS and water WCA analysis were used to understand surface activation mechanisms. In sum, Ar and Ar-O2 plasma jets can be used to modify the surfaces of these three substrates, although the latter relies on the generation of O radicals, while the former relies on OH radicals more. According to the results obtained by XPS analysis, the formation of C-O and C=O bond after plasma treatment is the main reason for surface activation in this study.

Inhibition of TNBC Breast Cancer Cell Proliferation and Mechanistic Study by Atmospheric Low Temperature Plasma

Inhibition of TNBC Breast Cancer Cell Proliferation and Mechanistic Study by Atmospheric Low Temperature Plasma

Investigation of the Effects of Atmospheric Low Temperature Plasma on Lung Adenocarcinoma Cells and Optimization of Treatment Conditions

Investigation of the Effects of Atmospheric Low Temperature Plasma on Lung Adenocarcinoma Cells and Optimization of Treatment Conditions

Effects of Atmospheric Low Temperature Plasma on Healing Mechanisms of Skin damage

Effects of Atmospheric Low Temperature Plasma on Healing Mechanisms of Skin damage

Bactericidal effect of low-temperature atmospheric plasma against the Shigella flexneri

BackgroundShigella flexneri (S. flexneri) is a common intestinal pathogenic bacteria that mainly causes bacillary dysentery, especially in low socioeconomic countries. This study aimed to apply cold atmospheric plasma (CAP) on S. flexneri directly to achieve rapid, efficient and environmentally friendly sterilization.MethodsThe operating parameters of the equipment were determined by plasma diagnostics. The plate count and transmission electron microscope were employed to calculate bacterial mortality rates and observe the morphological damage of bacterial cells. Measurement of intracellular reactive oxygen species (ROS) and superoxide anions were detected by 2,7-dichlorodihydrofluorescein (DCFH) and Dihydroethidium fluorescence probes, respectively. The fluorescence intensity (a. u.) reflects the relative contents. Additionally, the experiment about the single effect of temperature, ultraviolet (UV), and ROS on bacteria was conducted.ResultsThe peak discharge voltage and current during plasma operation were 3.92kV and 66mA. After discharge, the bacterial mortality rate of 10, 20, 30 and 40 s of plasma treatment was 60.71%, 74.02%, 88.11% and 98.76%, respectively. It was shown that the intracellular ROS content was proportional to the plasma treatment time and ROS was the major contributor to bacterial death.ConclusionIn summary, our results illustrated that the plasma treatment could inactivate S. flexneri efficiently, and the ROS produced by plasma is the leading cause of bacterial mortality. This highly efficient sterilization method renders plasma a highly promising solution for hospitals, clinics, and daily life.

Effect of low current cold atmospheric plasma on grains surface structure and water absorption capacity

The use of preparatory electrophysical methods of influencing food raw materials is one of the main trends in the development of innovative processes and technologies in the food and processing industry. Based on the physical effect of electron emission from a thermal emission source, a cold atmospheric plasma (CAP) was obtained, which was successfully applied to the grain material. Physical characteristics and evolution of low-temperature atmospheric plasma were considered as the main methods of analysis of electrophysical effects. To assess the effect of low-temperature plasma on grain material, measurements of water absorption capacity and analysis of surface modification by electron scanning microscopy were carried out. It has been experimentally established that CAP treatment contributes to a more intensive process of water absorption due to changes in the surface structure of the grain material. The total duration of the process of water absorption of grain material after processing of CAP decreased by more than three times until the equilibrium moisture content was reached. Scanning electron microscopy has shown that the processing of CAP leads to the appearance of a fine-mesh structure of the surface of the grain material. The effect of CAP treatment leads to modification of the seed surface, which consists in the manifestation of a fine-meshed structure on the surface of the seeds. Taking into account the advantages of CAP technology, namely the absence of the need for vacuuming and short processing time, the technology has a high practical potential.

Diagnostics of Atmospheric Plasma Jets of Helium and Argon Barrier Discharge in a Cylindrical Microwave Cavity Resonator

Introduction. Technologies related to the use of low-temperature atmospheric plasmas are developing at a rapid pace. Creation of new low-temperature plasma sources for specific applications requires monitoring of dynamic processes in such discharges with a high time resolution. Electron concentration is one the most important plasma characteristics, which can be very low for a low-temperature atmospheric pressure plasma. However, the methods currently available for diagnostics of gas-discharge plasmas are either characterized by insufficient sensitivity or unable to monitor dynamic processes in non-stationary discharges. In this regard, the development of new diagnostic approaches to low-temperature atmospheric plasma seems to be a relevant research direction.Aim. To develop a diagnostic method for an atmospheric plasma with a low gas temperature and a low electron concentration in a cylindrical microwave resonator.Materials and methods. The proposed diagnostic method is based on the well-known principle of measuring the frequency shift and the Q-factor of the eigenmodes of the microwave resonator, inside which the plasma under study is located.Results. Measurements of the atmospheric barrier discharge plasma jets in a helium and argon stream in a cylindrical microwave resonator were performed. The proposed geometry made it possible to significantly increase the sensitivity of measurements. It became possible to exclude the effect of polarization degeneracy in a round cylindrical resonator. The developed system was also tested on test objects with a known value of permittivity.Conclusion. A method for microwave diagnostics of stationary and non-stationary cold atmospheric plasma jets in a cylindrical resonator, inside which transmitting and receiving antennas are installed, as well as an orthogonal thin conductor preventing the excitation of undesirable modes, was developed.

Сушка яблочных чипсов с применением интеллектуальной обработки низкотемпературной атмосферной плазмой

The food industry needs more effective drying procedures that would maintain the quality of the original fruit or vegetable. Infrared drying combined with advanced electrophysical technologies may be a perfect solution. The present research objective was to study the effect of low-temperature atmospheric gas plasma treatment on the drying efficiency of apple slices.
 The research featured apples of the Idared variety (Russia) sliced into pieces of 5, 7, and 10 mm. The experiment involved the parameters of drying kinetics and moisture diffusion. The quality of the apple slices was assessed by the total content of phenols and flavonoids, generalized antiradical activity, color characteristics, and the Fourier transform infrared (FT-IR) spectrum.
 The electropores induced by the cold atmospheric gas plasma processing had a tree-like structure. The pre-treatment reduced the drying time by 18.0, 13.0 and 10.5% for the samples with a thickness of 5, 7, and 10 mm, respectively. The specific energy consumption decreased by 15–18%, depending on the slice thickness. The pre-treatment also increased the total content of phenols, flavonoids, and antiradical activity by 2.5–14.3, 19.1–25.9, and 8.3–35.4%, respectively.
 Therefore, the pre-treatment with cold atmospheric gas plasma reduced the drying time and preserved the original biologically active compounds in dried apple slices.

The quality by design approach for optimization of slayer exciter based low power portable atmospheric plasma jet on bactericidal efficacy of Pseudomonas aeruginosa.

A simple, portable, economical low-temperature atmospheric plasma (LTAP) for bactericidal efficacy of Gram-negative bacteria (Pseudomonas aeruginosa) with different carrier gases (argon, helium, and nitrogen) using the quality by design (QbD) approach, design of experiments (DoE), and response surface graphs (RSG) is presented. Box-Behnken design was used as the DoE to narrow down and further optimize the experimental factors of LTAP. Plasma exposure time, input DC voltage, and carrier gas flow rate were varied to examine the bactericidal efficacy using the zone of inhibition (ZOI). A higher bactericidal efficacy was achieved under the optimal bactericidal factors having ZOI of 50.837±2.418 mm2 with the plasma power density of 132 mW/cm3 for LTAP-Ar at 61.19 s, 14.8747 V, and 219.379 sccm than LTAP-He and LTAP-N2 . The LTAP-Ar was further evaluated at different frequencies and probe lengths to achieve a ZOI of 58.237±4.01 mm2 .

Hydroxyl‐initiated oxidation processes of phenylenediamines treated by the atmospheric plasma: A theoretical study in gas phase

AbstractThe low temperature atmospheric plasma are kinds of advanced oxidation processes (AOPs) reactors and have potential applications on gas cleaning and water treatment; however, the underlying reaction mechanisms of organic compounds degradation are not well understood. In this study, the gas phase multistep OH‐initiated dehydrogenations of p‐, m‐, and o‐phenylenediamine with C2h, C2, and C2 point groups were investigated using density functional theory. Intrinsic reaction calculations were performed for transition states at the M062X/Def2TZVPP level of theory. The distinct directed graphs of the predominant pathways are presented to elucidate the dehydrogenation processes of three isomers of phenylenediamines. The information reported in this paper reveals the AOPs of phenylenediamines.

Sublimation of Benign Conjunctival Nevi Using Plasma-Assisted Noninvasive Surgery: A Clinical Case Series.

Conjunctival nevi (CN) are common benign ocular tumors. Given their low risk of malignancy, surgical removal of nevi is primarily requested by patients. Herein, we introduce Atmospheric Low-temperature Plasma (ALTP) as a novel noninvasive method for the removal of CN. A clinical case series was conducted from 2020 to 2021 at the Vision Health Ophthalmic Center in Tehran, Iran. CN in one of the eyes of seven patients was treated. In all patients, the benignity of CN was confirmed by ocular oncologists. The white handpiece of the Plexr device, which generates plasma with the lowest output, was used to apply plasma spots on the nevi. In addition, the Ocular Surface Disease Index (OSDI) questionnaire was completed by all patients before and six months after the treatment. In all patients, the nevi outside the limbus area completely disappeared. The mean size of pre- and post-operative nevi was 3.89×11.7 and 0.54×1.69 mm, respectively. Results of the OSDI questionnaire showed significantly lower scores after the surgery in all patients. The ALTP method is a simple, cost-effective, and office-based surgery to remove CN safely and effectively.

Optimization of Atmospheric Low-Temperature Plasma to Reduce Side Effects in Colorectal Cancer

Optimization of Atmospheric Low-Temperature Plasma to Reduce Side Effects in Colorectal Cancer

Improving effects of low-temperature atmospheric plasma on abdominal surgical site infection induced by ESBL-E. coli in rats

Surgical site infection (SSI) is one of the most common complications of emergency abdominal surgery. With the increase of drug-resistant bacteria, abdominal SSI cannot be effectively controlled by increasing the use of antibiotics. Nonchemical treatment as an alternative to antibiotics for abdominal SSI induced by drug-resistant bacteria is urgently needed. This study is aimed at exploring the effects of low-temperature atmospheric plasma (LTAP) exposure for 30 and 60 s on abdominal SSI in in vitro and in vivo experiments. In the in vitro experiment, the culture dishes with extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-E. coli) were exposed to LTAP and the changes in bacterial concentration and structure were observed by bacterial culture counting and transmission electron microscopy (TEM). In in vivo experiments, we established an abdominal SSI rat model induced by ESBL-E. coli and the infected surgical sites were exposed to LTAP. The infiltration of inflammatory cells, the proliferation of fibroblasts, and the regeneration of fibrous tissue were evaluated by histopathological examination. The in vitro bacterial experiment showed that the concentration of bacteria exposed to LTAP for 30 and 60 s was decreased, and the decline in bacterial concentration in the last 30 s was significantly higher than that in the first 30 s. TEM showed that the bactericidal effect of the LTAP exposure worked by damaging the morphology and intracellular structures of bacteria. In addition, our data suggested that reactive oxygen species are the key mediator of the bactericidal effect, and bacteria exposed to LTAP do not develop resistance to repeated exposure. The pathological results from in vivo experiments revealed that the inflammatory cells infiltrating into the infected site were inhibited. The proliferation of fibroblasts and the regeneration of fibers increased after exposure to LTAP for 30 and 60 s in abdominal SSI. In conclusion, our study indicated that LTAP was effective in wound sterilization, anti-inflammatory action, and healing promotion and holds promise as an alternative to antibiotics for treating abdominal SSIs.

Albumin aggregation using low-temperature atmospheric pressure helium plasma jet in argon and air atmosphere

A mechanism of albumin aggregation using a low-temperature atmospheric pressure helium plasma jet was investigated. This aggregation is one of the most dominant processes in the plasma-induced hemostasis. Using a chamber where air and argon can be used as surrounding gas, the role of reactive nitrogen species on the aggregation of albumin was tested. By changing the surrounding gas, it is possible to control the production of reactive species. The experimental results show that the stability of plasma discharge seems more important for the aggregation of albumin than the presence of reactive nitrogen species. Moreover, it was shown that long lifetime species in the solution and exposure to UV light do not play a major role in the aggregation.

Potential formation on floating metal plate treated by low-temperature atmospheric pressure plasma jet

In the biomedical applications using low-temperature atmospheric pressure plasmas, charging on surface of the targets could play an important role. In this study, we have investigated potential formed on an electrically floating copper plate treated by a low-temperature atmospheric pressure helium plasma jet. The potential of the copper plate was measured by an electrostatic sensor in a non-contact manner. It was found that the potential on the copper plate could be controlled from 200 to −600 V by changing the distance between the nozzle of plasma device and the surface of copper plate. We discussed the charging mechanism such as collection of charged particles and several processes of electron emission including thermionic, field emission, secondary electron emission, and photoelectric processes.

Characterization on the Copolymerization Resin between Bayberry (Myrica rubra) Tannin and Pre-Polymers of Conventional Urea–Formaldehyde Resin

By focusing on the disadvantages of weak water resistance and high formaldehyde emission of urea–formaldehyde resin (UF), this research provides a new method to overcome these shortages of UF resin by using tannin for partial substitution of urea. Furthermore, plasma pretreatment of wood was introduced to strengthen the bonding performance of plywood. The investigation of the chemical structure of UF resin and tannin–urea–formaldehyde resin (TUF) were performed with Fourier transform infrared spectroscopy (FT-IR) and solid-state 13C nuclear magnetic resonance (13C NMR). The results of investigations confirmed the joining of tannin into the resin structure, which may enhance structural rigidity of TUF adhesives and improve hydrolysis stability. Then, thermal performance of UF resin and TUF resins were tested by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The DSC results indicated that the curing temperature did not change significantly. However, the TG analysis showed that the thermal stability of TUF resin was considerably improved. In bonding performance test, tannin–urea–formaldehyde resin (TUF) revealed an excellent water resistance, comparable to UF resin and can fulfill the standard requirement for plywood (Type II according to the Norm GB/T 17657-2013). It is interesting that the shear strength of wood specimens, bonded with TUF6 resin, after low-pressure cold plasma equipment (CLP plasma) and jet type atmospheric low-temperature plasma (JTLP plasma) treatment, reached 0.80 MPa and 0.85 MPa, respectively, after being soaked in boiling water for 3 h. In addition, most of the bonded plywood samples with TUF resin exhibited a lower formaldehyde emission, especially those prepared at 70 °C and 1.5 h, in which the formaldehyde emission amount could be reduced by approximately 39%.