DNA Strand Breaks and Denaturation as Probes of Chemical Reactivity versus Thermal Effects of Atmospheric Pressure Plasma Jets
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Results for “atmospheric pressure plasma jet”
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Tomographic Optical Imaging of a Pulsed Atmospheric Pressure Plasma Jet.
Abstract not provided.
Bentz, Brian↗
Tomographic Optical Imaging of a Pulsed Atmospheric Pressure Plasma Jet
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Bentz, Brian Zahler↗
Estimation of mean electron energy in helium surface ionization waves on dielectric substrates
Abstract The determination of basic plasma parameters in atmospheric pressure discharges is critical to advancing their use in applications. Atmospheric pressure plasma jets have found use in the fields of medicine, agriculture, material modification and others. Atmospheric pressure plasma jets often generate plasma surface ionization waves (SIW) which interact with and propagate over surfaces. Electrical diagnostics are challenging in SIW due to high collision frequencies and small scale of the plasma discharge. This work employs a passive optical emission line ratio technique to estimate the mean electron energy in SIW over planar dielectric substrates. The method uses an intensity ratio of two helium triplet lines: He( 3 3 S ) at 706.5 nm and He( 3 3 D ) at 587.56 nm. A collisional-radiative model is used to correlate line ratio to mean electron energy and determine dependencies on electron density and He/air gas mixture. Mean electron energies ranging from 3–8 eV are determined in He/air mixtures and are found to remain constant as the surface wave propagates radially. This work provides a 2D, time-resolved, mean electron energy diagnostic for surface ionization wave propagation and validation of numerical modeling in atmospheric pressure systems with spatially varying He/air gas mixtures. The model in question is designed for use with any He line ratio in the n = 3 excitation level.
Morsell, Joshua (ORCID:0000000331073002)↗
Electric field dynamics in an atmospheric pressure helium plasma jet impinging on a substrate
Time and spatially resolved electric field measurements by Stark polarization spectroscopy in a nanosecond pulsed atmospheric pressure helium jet operating in ambient air and impinging on a conductive indium tin oxide (ITO) coated glass slide are reported. An automatic fitting procedure of the Stark shifted spectra taking into consideration constraints regarding Stark components positions and intensities as well as molecular nitrogen emission subtraction was implemented. This allowed electric field vector components measurements both in the gas phase and at the interface when the jet impinges on the substrate and during the development of a surface ionization wave. The obtained results show an increase of the axial electric field in the jet effluent in the gas phase with a peak magnitude from 12 to 18 kVcm -1 before the ionization wave impinges on the substrate. A steep electric field enhancement to a peak value of about 24 kVcm -1 was observed when the ionization wave impinges on the surface. A peak radial electric field of about 27 kVcm -1 was measured off-axis in the surface ionization wave. These results are consistent with previously reported modelling predictions. While Stark polarization spectroscopy is limited to electric field measurement from regions with emission, we illustrate that the capability to measure near surface electric fields in helium makes it a valuable complementary technique for the electric field-induced second harmonic (E-FISH) technique.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Method of generation of planar plasma jets
Applications of dielectric barrier discharge (DBD) based atmospheric pressure plasma jets are often limited by the relatively small area of treatment due to their 1D configuration. This system generates 2D plasma jets permitting fast treatment of larger targets. DBD evolution starts with formation of transient anode glow, and continues with development of cathode-directed streamers. The anode glow can propagate as an ionization wave along the dielectric surface through and outside of the discharge gap. Plasma propagation is not limited to 1D geometry such as tubes, and can be organized in a form of a rectangular plasma jet, or other 2D or 3D shapes. Also described are a method for generating 2D plasma jets and use of the 2D plasma jets for cancer therapy.
Dobrynin, Danil V.↗
Mitigating the allergenicity of peanut allergen Ara h 1 by cold atmospheric pressure argon plasma jet
Abstract BACKGROUND Peanut allergy is recognized as a major food allergy that triggers severe and even fatal symptoms. Avoidance of peanuts in the diet is the main option for current safety management. Processing techniques reducing peanut allergenicity are required to develop other options. Cold plasma is currently considered as a novel non‐thermal approach to alter protein structure and has the potential to alleviate immunoreactivity of protein allergen. RESULTS The application of a cold argon plasma jet to peanut protein extract could reduce the amount of a 64 kDa protein band corresponding to a major peanut allergen Ara h 1 using sodium dodecyl sulfate–polyacrylamide gel electrophoresis, but the overall protein size distribution did not change significantly. A decrease in peanut protein solubility was a possible cause that led to the loss of protein content in the soluble fraction. Immunoblotting and enzyme‐linked immunosorbent assay elucidated that the immunoreactivity of Ara h 1 was significantly decreased with the time treated with plasma. Ara h 1 antigenicity reduced by 38% after five scans (approximately 3 min) of cold argon plasma jet treatment, and the reduction was up to 66% after approximately 15 min of treatment. CONCLUSION The results indicate that cold argon plasma jet treatment could be a suitable platform for alleviating the immunoreactivity of peanut protein. This work demonstrates an efficient, compact, and rapid platform for mitigating the allergenicity of peanuts, and shows great potential for the plasma platform as a non‐thermal technique in the food industry. © 2023 Society of Chemical Industry.
Hsu, Fu‐Chiun↗
Autonomous Aerosol and Plasma Co‐Jet Printing of Metallic Devices at Ambient Temperature
Abstract Additive manufacturing of metallic materials holds the potential to revolutionize the fabrication of functional devices unattainable via traditional methods. Despite recent advancements, printing metallic materials typically requires thermal processing at elevated temperatures to form dense structures with desired properties, which presents a major challenge for direct printing and integration with temperature‐sensitive materials. Herein, a unique co‐jet printing (CJP) method is reported integrating an aerosol jet and a non‐thermal, atmospheric pressure plasma jet to enable concurrent aerosol deposition of metal nanoparticle inks and in situ sintering at ambient temperature. A machine learning algorithm is integrated with the CJP to perform real‐time defect detection and autonomous correction, enhancing the yield of printed films with high electrical conductivity from 44% to 94%. Concurrent printing and sintering eliminate the need for post‐printing processing, reducing the overall manufacturing time by multiple folds depending on product size. CJP enables direct printing of functional devices on a variety of temperature‐sensitive materials including biological materials. Direct printing of hydration sensors on living plant leaves is demonstrated for long‐duration monitoring of hydration level in the plant. The versatile CJP method opens tremendous opportunities to harmoniously integrate abiotic and biotic materials for emerging applications in wearable/implantable devices and biohybrid systems.
Du, Yipu [Department of Aerospace and Mechanical E↗
Guided plasma jets directed onto wet surfaces: angular dependence and control
The optimal use of atmospheric pressure plasma jets (APPJs) for treatment of surfaces—inorganic, organic and liquid—depends on being able to control the flow of plasma-generated reactive species onto the surface. The typical APPJ is a rare gas mixture (RGM) flowed through a tube to which voltage is applied, producing an RGM plasma plume that extends into the ambient air. The RGM plasma plume is guided by a surrounding shroud of air due to the higher electric field required for an ionization wave (IW) to propagate into the air. Additionally, the mixing of the ambient air with the RGM plasma plume then determines the production of reactive oxygen and nitrogen species (RONS). The APPJ is usually oriented perpendicular to the surface being treated. However, the angle of the APPJ with respect to the surface may be a method to control the production of reactive species to the surface due to the change in APPJ propagation properties and the resulting gas dynamics. In this paper, we discuss results from computational and experimental investigations addressing two points—propagation of IWs in APPJs with and without a guiding gas shroud as a function of angle of the APPJ with respect to the surface; and the use of this angle to control plasma activation of thin water layers. We found that APPJs propagating out of the plasma tube into a same-gas environment lack any of the directional properties of shroud-guided jets, and largely follow electric field lines as the angle of the plasma tube is changed. Guided APPJs propagate coaxially with the tube as the angle is changed, and turn perpendicularly towards the surface only a few mm above the surface. The angle of the APPJ produces different gas dynamic distributions, which enable some degree of control over the content of RONS transferred to thin water layers.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Spatially and temporally resolved H and OH densities in a nanosecond pulsed plasma jet: an analysis of the radical generation, transport, recombination and memory effects
Not Available
Yue, Yuanfu (ORCID:0000000247940708)↗
Atmospheric pressure plasmas interacting with wet and dry microchannels: reverse surface ionization waves
Atmospheric pressure plasma jets (APPJs) are increasingly being used to functionalize polymers and dielectric materials for biomedical and biotechnology applications. Once such application is microfluidic labs-on-a-chip consisting of dielectric slabs with microchannel grooves hundreds of microns in width and depth. The periodic channels, an example of a complex surface, present challenges in terms of directly and uniformly exposing the surface to the plasma. In this paper, we discuss results from computational and experimental investigations of negative APPJs sustained in Ar/N 2 mixtures flowing into ambient air and incident onto a series of microchannels. Results from two-dimensional plasma hydrodynamics modeling are compared to experimental measurements of electric field and fast-camera imaging. The propagation of the plasma across dry microchannels largely consists of a sequence of surface ionization waves (SIWs) on the top ridges of the channels and bulk ionization waves (IWs) crossing over the channels. The IWs are directed into electric field enhanced vertices of the next ridge. The charging of these ridges produce reverse IWs responsible for the majority of the ionization. The propagation of the plasma across water filled microchannels evolve into hopping SIWs between the leading edges of the water channels, regions of electric enhancement due to polarization of the water. Positive, reverse IWs follow the pre-ionized path of the initial negative waves.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
N 2 vibrational excitation in atmospheric pressure ns pulse and RF plasma jets
Time-resolved N 2 vibrational temperature and translational–rotational temperature in quasi-two-dimensional atmospheric pressure plasma jets sustained by ns pulse and RF discharges in nitrogen/noble gas mixtures are measured by the broadband vibrational Coherent Anti-Stokes Raman Scattering (CARS) . The results indicate a much stronger vibrational excitation in the RF plasma jet, due to the lower reduced electric field and higher discharge power. In a ns pulse discharge in N 2 /He, N 2 vibrational temperature is significantly lower compared to that in N 2 /Ar, due to the more rapid vibration–translation (V–T) relaxation of nitrogen by helium atoms. In the RF plasma jets in N 2 /Ne and N 2 /Ar, the vibrational excitation increases considerably as the nitrogen fraction in the mixture is reduced. The experimental data in the RF plasma jet in N 2 /Ar jet are compared with the kinetic modeling predictions. The results indicate that nitrogen vibrational excitation in N 2 /Ar plasma jets with a small N 2 fraction in the mixture (several percent) is controlled primarily by electron impact, anharmonic vibration–vibration (V–V) pumping, and V–T relaxation by N atoms. In comparison, V–V energy transfer from the vibrationally excited molecules in the first excited electronic state, N 2 (A 3 Σ u + , v), which are generated primarily by the energy transfer from the metastable Ar atoms, has a minor effect on the vibrational populations of the ground electronic state, N 2 (X 1 Σ g + , v). Although the discharge energy fraction going to electronic excitation is significant, the predicted quasi-steady-state N 2 (A 3 Σ u + ) number density, controlled by the energy pooling and quenching by N atoms, remains relatively low. Because of this, the net rate of N 2 (X 1 Σ g + ) vibrational excitation by the V–V energy transfer from N 2 (A 3 Σ u + ) is much lower compared to that by the direct electron impact. Furthermore, the results show that atmospheric pressure RF plasma jets can be used as sources of highly vibrationally excited N 2 molecules and N atoms.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Electrochemical Structure of the Plasma–Liquid Interface
Nonthermal atmospheric pressure plasma in contact with a liquid yields a variety of energetic photons, ions, and electrons, which can be transported into the plasma–liquid interface (PLI). Similar to the electrochemical interface formed between a solid electrode and electrolyte in conventional electrochemical systems, the charge-transfer process across the PLI is able to promote reduction–oxidation (redox) reactions. However, in the case of free plasma jets in contact with liquids, the absence of solid electrodes obscures the spatial locations of the electrochemical half-reactions. Herein, we present a spatial electrochemical measurement technique used to characterize an aqueous solution in contact with an atmospheric pressure plasma jet. The technique is based on measuring the potential difference between two identical Ag/AgCl electrochemical electrodes positioned at different locations within the solution. More specifically, electrochemical maps were made by measuring the potential of one electrochemical electrode positioned at different locations near the PLI with respect to the other electrochemical electrode positioned far away from the PLI in the bulk solution. Regions in the map with negative and positive potential differences between these electrochemical electrodes were used to identify the electrodeless cathode and anode, respectively. Here, visualization of the spatial distribution of molecular colorimetric redox indicators by multispectral imaging revealed that reduction was occurring near the plasma jet centerline while oxidation was occurring further away in solution, which constitutes an independent confirmation of the electrochemical maps.
Absorption↗
Atmospheric pressure plasma treatment of skin: penetration into hair follicles
Sterilization of skin prior to surgery is challenged by the reservoir of bacteria that resides in hair follicles. Atmospheric pressure plasma jets (APPJs) have been proposed as a method to treat and deactivate these bacteria as atmospheric plasmas are able to penetrate into structures and crevices with dimensions similar to those found in hair follicles. In this paper, we discuss results from a computational investigation of an APPJ sustained in helium flowing into ambient air, and incident onto a layered dielectric similar to human skin in which there are idealized hair follicles. We found that, depending on the location of the follicle, the bulk ionization wave (IW) incident onto the skin, or the surface IW on the skin, are able to launch IWs into the follicle. The uniformity of treatment of the follicle depends on the location of the first entry of the plasma into the follicle on the top of the skin. Typically, only one side of the follicle is treated on for a given plasma pulse, with uniform treatment resulting from rastering the plasma jet across the follicle over many pulses. Plasma treatment of the follicle is sensitive to the angle of the follicle with respect to the skin, width of the follicle pocket, conductivity of the dermis and thickness of the underlying subcutaneous fat layer, the latter due to the change in capacitance of the tissue.
60 APPLIED LIFE SCIENCES↗
Molecular beam mass spectrometry measurements of vibrationally excited N 2 in the effluent of an atmospheric plasma jet: a comparison with a state-to-state kinetic model
Vibrationally excited N 2 molecules are suggested to be one of the possible key species responsible for the observed synergistic effects in plasma catalysis for NH 3 synthesis. To assess the impact of vibrationally excited species in plasma-catalysis, quantitative measurements near interfaces are required, which remains challenging. In this letter, we report spatially resolved measurements of vibrationally excited N 2 in the effluent of an atmospheric pressure plasma jet by molecular beam mass spectrometry (MBMS). The mass spectrometry signals as a function of electron energy of the ionizer were fitted with the effective electron-impact ionization cross section of N 2 (v) considering the vibrational distribution function as determined by a detailed vibrational level resolved plasma kinetic calculation. Here, the reported method presented in this letter shows the capability of MBMS to measure vibrationally excited species of N 2 near interfaces when the vibrational distribution function is known or assumed and shows excellent agreement with state-to-state kinetic models of N 2 (v).
42 ENGINEERING↗
Investigation of Ni catalyst activation during plasma-assisted methane oxidation
Atmospheric pressure plasma has shown promise in improving thermally activated catalytic reactions through a process termed plasma-catalysis synergy. In this work, we investigated atmospheric pressure plasma jet (APPJ)-assisted CH 4 oxidation over a Ni/SiO 2 .Al 2 O 3 catalyst. Downstream gas-phase products from CH 4 conversion were quantified by Fourier transform infrared spectroscopy. The catalyst near-surface region was characterized by in-situ diffuse reflectance infrared Fourier transform spectroscopy. The catalyst was observed to be activated at elevated temperature (500 °C) if it was exposed to the APPJ operated at large plasma power. 'Catalyst activation' signifies that the purely thermal conversion of CH 4 using catalysts which had been pre-exposed to plasma became more intense and produced consistently CO product, even if the plasma was extinguished. Without the application of the APPJ to the Ni catalyst surface this was not observed at 500 °C. The study of different exposure conditions of the activated catalyst indicates that the reduction of the catalyst by the APPJ is likely the cause of the catalyst activation. We also observed a systematic shift of the vibrational frequency of adsorbed CO on Ni catalyst when plasma operating conditions and catalyst temperatures were varied and discussed possible explanations for the observed changes. Furthermore, this work provides insights into the plasma-catalyst interaction, especially catalyst modification in the plasma catalysis process, and potentially demonstrates the possibility of utilizing the surface CO as a local probe to understand the plasma-catalyst interaction and shed light on the complexity of plasma catalysis.
methane oxidation↗