Barrier discharges (BDs) produce highly non-equilibrium plasmas in a controllable way at atmospheric pressure, and at moderate gas temperature. They provide the effective generation of atoms, radicals and excited species by energetic electrons. In the case of operation in noble gases (or noble gas/halogen gas mixtures), they are sources of an intensive UV and VUV excimer radiation. There are two different modes of BDs. Generally they are operated in the filamentary one. Under special conditions, a diffuse mode can be generated. Their physical properties are discussed, and the main electric parameters, necessary for the controlled BD operation, are listed. Recent results on spatially and temporally resolved spectroscopic investigations by cross-correlation technique are presented. BDs are applied for a long time in the wide field of plasma treatment and layer deposition. An overview on these applications is given. Selected representative examples are outlined in more detail. In particular, the surface treatment by filamentary and diffuse BDs, and the VUV catalyzed deposition of metallic layers are discussed. BDs have a great flexibility with respect to their geometrical shape, working gas mixture and operation parameters. Generally, the scaling-up to large dimensions is of no problem. The possibility to treat or coat surfaces at low gas temperature and pressures close to atmospheric once is an important advantage for their application.

Water disinfection by indirect plasma treatment was investigated using a surface dielectric barrier discharge (DBD). Liquid was neither part of the discharge electrode configuration nor stirred during plasma treatment. High concentrations (106–108 cfu·mL−1) of Escherichia coli and Staphylococcus aureus have been completely inactivated within 5–15 min, depending on liquid sample volume. Inactivation occurred in non‐buffered liquids, only, where pH decrease was found. Measurements of pH, nitrate, and nitrite concentrations after DBD plasma or NO gas treatment lead to the conclusion that nitric acid formation from plasma‐generated reactive nitrogen species are the main source of liquid acidification. Incubation of bacteria in nitric acid alone did not result in comparable inactivation effects. Increase of H2O2 concentration was found as a result of plasma treatment of liquids but not after treatment by NO gas. Therefore, synergistic action of both reactive oxygen and nitrogen species are discussed to be responsible for antimicrobial plasma effects.

Dielectric barrier discharges (DBDs) are plasmas generated in configurations with an insulating (dielectric) material between the electrodes which is responsible for a self-pulsing operation. DBDs are a typical example of nonthermal atmospheric or normal pressure gas discharges. Initially used for the generation of ozone, they have opened up many other fields of application. Therefore DBDs are a relevant tool in current plasma technology as well as an object for fundamental studies. Another motivation for further research is the fact that so-called partial discharges in insulated high voltage systems are special types of DBDs. The breakdown processes, the formation of structures, and the role of surface processes are currently under investigation. This review is intended to give an update to the already existing literature on DBDs considering the research and development within the last two decades. The main principles and different modes of discharge generation are summarized. A collection of known as well as special electrode configurations and reactor designs will be presented. This shall demonstrate the different and broad possibilities, but also the similarities and common aspects of devices for different fields of applications explored within the last years. The main part is devoted to the progress on the investigation of different aspects of breakdown and plasma formation with the focus on single filaments or microdischarges. This includes a summary of the current knowledge on the electrical characterization of filamentary DBDs. In particular, the recent new insights on the elementary volume and surface memory mechanisms in these discharges will be discussed. An outlook for the forthcoming challenges on research and development will be given.

To cite this version:J EhlbeckAbstract. The aim of this article is to provide a survey of plasma sources at atmospheric pressure used for microbicidal treatment. In order to consider the interdisciplinary character of this topic an introduction and definition of basic terms and procedures is given for plasma as well as for microbicidal issues. The list of plasma sources makes no claim to be complete, but to represent the main principles of plasma generation at atmospheric pressure and to give an example of their microbicidal efficiency. The interpretation of the microbicidal results remain difficult due to the non standardized methods uses by different authors and due to the fact that small variations in the set up can change the results dramatically.

The technique of spatially resolved cross-correlation spectroscopy (CCS) is used to carry out diagnostic measurements of the barrier discharge (BD) in air at atmospheric pressure. Quantitative estimates for electric field strength E(x, t) and for relative electron density n e (x, t)/n max e are derived from the experimentally determined spatio-temporal distributions of the luminosity for the spectral bands of the 0-0 transitions of the second positive system of N 2 (λ = 337.1 nm) and the first negative system of N + 2 (λ = 391.5 nm). These results are used to test the validity of some physical models of electrical breakdown in a BD. The influence of the spatio-temporal structure of the discharge on the chemical kinetics of ozone synthesis is studied by means of a semi-empirical method based on the results of spatially resolved CCS measurements.

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Atmospheric pressure plasma jets have a long history of more than 50 years. During this time their design and plasma generation mechanism has been developed and adapted to various fields of applications. This review aims at giving an overview of jet devices by starting with a brief history of their development. This is followed by an overview of commonly used terms and definitions as well as a survey of different classification schemes (e.g. geometry, excition frequency or specific energy input) described in literature. A selective update of new designs and novel research achievments on atmospheric pressure plasma jets published in 2012 or later shows the impressive variety and rapid development of the field. Finally, a brief outlook on the future trends and directions is given.

Plasma-based treatment of chronic wounds or skin diseases as well as tissue engineering or tumor treatment is an extremely promising field. First practical studies are promising, and plasma medicine as an independent medical field is emerging worldwide. While during the last years the basics of sterilizing effects of plasmas were well studied, concepts of tailor-made plasma sources which meet the technical requirements of medical instrumentation are still less developed. Indeed, studies on the verification of selective antiseptic effects of plasmas are required, but the development of advanced plasma sources for biomedical applications and a profound knowledge of their physics, chemistry, and parameters must be contributed by physical research. Considering atmospheric-pressure plasma sources, the determination of discharge development and plasma parameters is a great challenge, due to the high complexity and limited diagnostic approaches. This contribution gives an overview on plasma sources for therapeutic applications in plasma medicine. Selected specific plasma sources that are used for the investigation of various biological effects are presented and discussed. Furthermore, the needs, prospects, and approaches for its characterization from the fundamental plasma physical point of view will be discussed.