Browsing by Author "Reuter, Stephan"

Now showing 1 - 8 of 8
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    Detection of HO2 in an atmospheric pressure plasma jet using optical feedback cavity-enhanced absorption spectroscopy
    (London : IOP, 2016) Gianella, Michele; Reuter, Stephan; Aguila, Ana Lawry; Ritchie, Grant A. D.; Helden, Jean-Pierre H. van
    Cold non-equilibrium atmospheric pressure plasma jets are increasingly applied in material processing and plasma medicine. However, their small dimensions make diagnosing the fluxes of generated species a challenge. Here we report on the detection of the hydroperoxyl radical,HO2, in the effluent of a plasma jet by the use of optical feedback cavity-enhanced absorption spectroscopy. The spectrometer has aminimumdetectable absorption coefficient amin of 2.25 ´10-10 cm−1 with a 100 second acquisition, equivalent to 5.5 ´ 1012 cm-3 ofHO2 (under ideal conditions). Concentrations in the range of (3.1–7.8) ×1013 cm−3 were inferred in the 4mmwide effluent of the plasma jet.
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    The kINPen—a review on physics and chemistry of the atmospheric pressure plasma jet and its applications
    (Bristol : IOP Publ., 2018-5-16) Reuter, Stephan; von Woedtke, Thomas; Weltmann, Klaus-Dieter
    The kINPen® plasma jet was developed from laboratory prototype to commercially available non-equilibrium cold plasma jet for various applications in materials research, surface treatment and medicine. It has proven to be a valuable plasma source for industry as well as research and commercial use in plasma medicine, leading to very successful therapeutic results and its certification as a medical device. This topical review presents the different kINPen plasma sources available. Diagnostic techniques applied to the kINPen are introduced. The review summarizes the extensive studies of the physics and plasma chemistry of the kINPen performed by research groups across the world, and closes with a brief overview of the main application fields.
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    Non-thermal plasma treatment induces MAPK signaling in human monocytes
    (Berlin : de Gruyter, 2014) Bundscherer, Lena; Nagel, Stefanie; Hasse, Sybille; Tresp, Helena; Wende, Kristian; Walther, Reinhard; Reuter, Stephan; Weltmann, Klaus-Dieter; Masur, Kai; Lindequist, Ulrike
    The application of non-thermal atmospheric pressure plasma raises a hope for the new wound healing strategies. Next to its antibacterial effect it is known to stimulate skin cells. However, monocytes are also needed for the complex process of a wound healing. This study investigates the impact of plasma on the intracellular signaling events in the primary human monocytes. The proliferative MEK-ERK (MAPK/ERK kinase-extracellular signal-regulated kinase) pathway was activated by short plasma treatment times. In contrast, an induction of the apoptotic JNK (c-Jun N-terminal kinase) cascade as well as activation of caspase 3 were observed after long plasma exposure. These findings indicate that monocytes can be differentially stimulated by plasma treatment and may contribute to the proper wound recovery.
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    On the plasma chemistry of a cold atmospheric argon plasma jet with shielding gas device
    (Bristol : IOP Publ., 2016) Schmidt-Bleker, Ansgar; Winter, Jörn; Bösel, André; Reuter, Stephan; Weltmann, Klaus-Dieter
    A novel approach combining experimental and numerical methods for the study of reaction mechanisms in a cold atmospheric Ar plasma jet is introduced. The jet is operated with a shielding gas device that produces a gas curtain of defined composition around the plasma plume. The shielding gas composition is varied from pure N2 to pure O2. The density of metastable argon Ar(4s,3 P ) 2 in the plasma plume was quantified using laser atom absorption spectroscopy. The density of long-living reactive oxygen and nitrogen species (RONS), namely O3, NO2, NO, N O2 , N2O5 and H2O2, was quantified in the downstream region of the jet in a multipass cell using Fourier-transform infrared spectroscopy (FTIR). The jet produces a turbulent flow field and features guided streamers propagating at several km s-1 that follow the chaotic argon flow pattern, yielding a plasma plume with steep spatial gradients and a time dependence on the ns scale while the downstream chemistry unfolds within several seconds. The fast and highly localized electron impact reactions in the guided streamer head and the slower gas phase reactions of neutrals occurring in the plasma plume and experimental apparatus are therefore represented in two separate kinetic models. The first electron impact reaction kinetics model is correlated to the LAAS measurements and shows that in the guided streamer head primary reactive oxygen and nitrogen species are dominantly generated from Ar(4s,3 P2). The second neutral species plug-flow model hence uses an Ar(4s,3 P2) source term as sole energy input and yields good agreement with the RONS measured by FTIR spectroscopy.
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    One-Step Liquid Phase Polymerization of HEMA by Atmospheric-Pressure Plasma Discharges for Ti Dental Implants
    (Basel : MDPI, 2021) Buxadera-Palomero, Judit; Fricke, Katja; Reuter, Stephan; Gil, Francisco Javier; Rodriguez, Daniel; Canal, Cristina
    Dental implants can fail due to various factors, in which bad tissue integration is believed to have a significant role. Specific properties of the implant surface, such as its chemistry and roughness, are of paramount importance to address specific cell responses, such as the adsorption of proteins, as well as the adhesion and differentiation of cells, which are suitable for biomaterial and tissue engineering. In this study, an acrylate-containing coating was produced on titanium surfaces through the atmospheric pressure plasma treatment of a liquid precursor, 2-hydroxyethyl methacrylate. A hydrophilic coating was obtained, showing retention of the monomer chemistry as assessed by FTIR analysis and XPS. Enhanced fibroblast adhesion and decreased Staphylococcus aureus and Escherichia coli adhesion were recorded, showing that this is a suitable method to produce biocompatible coatings with a reduced bacterial adhesion.
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    Quantification of the ozone and singlet delta oxygen produced in gas and liquid phases by a non-thermal atmospheric plasma with relevance for medical treatment
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2018-8-15) Jablonowski, Helena; Santos Sousa, Joao; Weltmann, Klaus-Dieter; Wende, Kristian; Reuter, Stephan
    In the field of plasma medicine, the identification of relevant reactive species in the liquid phase is highly important. To design the plasma generated species composition for a targeted therapeutic application, the point of origin of those species needs to be known. The dominant reactive oxygen species generated by the plasma used in this study are atomic oxygen, ozone, and singlet delta oxygen. The species density changes with the distance to the active plasma zone, and, hence, the oxidizing potential of this species cocktail can be tuned by altering the treatment distance. In both phases (gas and liquid), independent techniques have been used to determine the species concentration as a function of the distance. The surrounding gas composition and ambient conditions were controlled between pure nitrogen and air-like by using a curtain gas device. In the gas phase, in contrast to the ozone density, the singlet delta oxygen density showed to be more sensitive to the distance. Additionally, by changing the surrounding gas, admixing or not molecular oxygen, the dynamics of ozone and singlet delta oxygen behave differently. Through an analysis of the reactive species development for the varied experimental parameters, the importance of several reaction pathways for the proceeding reactions was evaluated and some were eventually excluded.
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    Review on VUV to MIR absorption spectroscopy of atmospheric pressure plasma jets
    (Bristol : IOP Publ., 2015) Reuter, Stephan; Sousa, Joao Santos; Stancu, Gabi Daniel; Hubertus van Helden, Jean-Pierre
    Absorption spectroscopy (AS) represents a reliable method for the characterization of cold atmospheric pressure plasma jets. The method's simplicity stands out in comparison to competing diagnostic techniques. AS is an in situ, non-invasive technique giving absolute densities, free of calibration procedures, which other diagnostics, such as laser-induced fluorescence or optical emission spectroscopy, have to rely on. Ground state densities can be determined without the knowledge of the influence of collisional quenching. Therefore, absolute densities determined by absorption spectroscopy can be taken as calibration for other methods. In this paper, fundamentals of absorption spectroscopy are presented as an entrance to the topic. In the second part of the manuscript, a review of AS performed on cold atmospheric pressure plasma jets, as they are used e.g. in the field of plasma medicine, is presented. The focus is set on special techniques overcoming not only the drawback of spectrally overlapping absorbing species, but also the line-of-sight densities that AS usually provides or the necessity of sufficiently long absorption lengths. Where references are not available for measurements on cold atmospheric pressure plasma jets, other plasma sources including low-pressure plasmas are taken as an example to give suggestions for possible approaches. The final part is a table summarizing examples of absorption spectroscopic measurements on cold atmospheric pressure plasma jets. With this, the paper provides a 'best practice' guideline and gives a compendium of works by groups performing absorption spectroscopy on cold atmospheric pressure plasma jets.
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    Zentrum für Innovationskompetenz: Strategische Investitionen zur nachhaltigen Etablierung des ZIK plasmatis : Abschlussbericht zum Forschungsvorhaben mit dem FKZ: 03Z2DS1 ; Projektlaufzeit: 01.07.2013 - 31.01.2014
    (Hannover : Technische Informationsbibliothek (TIB), 2014) Weltmann, Klaus-Dieter; Reuter, Stephan; Masur, Kai
    [no abstract available]