Perspective: The Physics, Diagnostics, and Applications of Atmospheric Pressure Low Temperature Plasma Sources Used in Plasma Medicine

Low temperature plasmas have been used in various plasma processing applications for several decades. But it is only in the last thirty years or so that sources generating such plasmas at atmospheric pressure in reliable and stable ways have become more prevalent. First, in the late 1980s, the dielectric barrier discharge was used to generate relatively large volume diffuse plasmas at atmospheric pressure. Then, in the early 2000s, plasma jets that can launch cold plasma plumes in ambient air were developed. Extensive experimental and modeling work was carried out on both methods and much of the physics governing such sources was elucidated. Starting in the mid-1990s, low temperature plasma discharges have been used as sources of chemically reactive species that can be transported to interact with biological media, cells, and tissues and induce impactful biological effects. However, many of the biochemical pathways whereby plasma affects cells remain not well understood. This situation is changing rather quickly because the field, known today as plasma medicine, has experienced exponential growth in the last few years thanks to a global research community that engaged in fundamental and applied research involving the use of cold plasma for the inactivation of bacteria, dental applications, wound healing, and the destruction of cancer cells/tumors. In this perspective, the authors first review the physics as well as the diagnostics of the principal plasma sources used in plasma medicine. Then, brief descriptions of their biomedical applications are presented. To conclude, the authors\u27 personal assessment of the present status and future outlook of the field is given. Published by AIP Publishing

Ultra-short pulsed non-equilibrium atmospheric pressure gas discharges

This thesis presents experimental studies of various non-thermal atmospheric pressure gas discharges generated using short pulsed excitation as an alternative to widely used sinusoidal excitation. Several pulse generators are detailed that provide high voltage pulses ranging from hundreds of microseconds to less than ten nanoseconds in duration. A key enabler to the generation of a stable discharge is a suitably high repetition rate; this prerequisite precludes many conventional pulsed power technologies. Fortunately, recent advances in semiconductor technology have made it possible to construct solid state switches capable of producing high voltage pulses with repetition rates of many kilohertz. Pulsed excitation introduces many opportunities to tailor the applied voltage and consequently enhance the discharge which are not possible with sinusoidal excitation sources. Through detailed electrical and optical analysis it is shown that pulsed excitation is not only more energy efficient than a comparable sinusoidal source but produces a higher flux of excited species that are essential in many applications. When pulse widths are reduced to a sub-microsecond timescale a novel barrier-free mode of operation is observed. It is shown that diffuse large area plasmas are easily produced at kilohertz repetition rates without the usually indispensable dielectric barriers. Experimental results show that a short pulse width prevents the onset of the undesirable glow-to-arc transition thus introducing an added degree of stability. A further benefit of pulsed excitation is the ability to produce gas discharges with a high instantaneous peak power yet low average power consumption, resulting in a high density plasma that exhibits roomtemperature characteristics. Finally, as an acid test to highlight the many benefits of pulsed excitation several real-world applications are considered. It is shown that in all cases pulsed gas discharges provide real benefits compared to their sinusoidal counterparts

Frontiers in Atmospheric Pressure Plasma Technology

Atmospheric pressure plasma discharges have grown rapidly in importance in recent decades, due to the ease in handling and operation, plus their eco-friendly applications, for agriculture, food, medicine, materials and even the automotive and aerospace industries. In this context, the need for a collection of results based on plasma technologies is justified. Moreover, at the international level, the increased number of projects that translated to publications and patents in the multidisciplinary field of plasma-based technology gives researchers the opportunity to challenge their knowledge and contribute to a new era of green services and products that society demands. Therefore, this book, based on the Special Issue of “Frontiers in Atmospheric Pressure Plasma Technology” in the “Applied Physics” section of the journal Applied Sciences, provides results on some plasma-based methods and technologies for novel and possible future applications of plasmas in life sciences, biomedicine, agriculture, and the automotive industry.This book, entitled “Frontiers in Atmospheric Pressure Plasma Technology”, consists of 8 research articles, 2 review articles and 1 editorial. We know that we are only managing to address a small part of what plasma discharge can be used for, but we hope that the readers will enjoy this book and, therefore, be inspired with new ideas for future research in the field of plasma

The kINPen—a review on physics and chemistry of the atmospheric pressure plasma jet and its applications

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

Cold Plasma

Non-equilibrium plasma (or low-temperature plasma, LTP) offers a chemically rich medium without the need for high power and elevated temperatures. This unique characteristic has made LTP very useful for various industrial and biomedical applications where thermal effects are not desirable. In addition, the relative simplicity of the design of sources capable of generating non-equilibrium plasma at atmospheric pressure makes LTP a very attractive technology that can accomplish the same or better results than much more complex and expensive approaches. This book describes various low-temperature plasma sources and some of their environmental and biomedical applications. The plasma sources covered in this book include low-temperature plasma jets which are novel devices that can launch low-power, low-temperature plasma plumes in ambient air. These plasma plumes can accurately and reliably be aimed at a surface to be treated or at a biological target such as cells and tissues. The application of these plasma jets in medicine, including in cancer therapy, are thoroughly discussed in this book. The contents of this book will appeal to engineers, medical experts, academics, and students who work with plasma technology

Development and optimization of low power non-thermal plasma jet operational parameters for treating dyes and emerging contaminants

Emerging contaminants (ECs) have come out as the latest class of environmental contaminants, which are highly recalcitrant and toxic in nature. Currently, no suitable rectification methods are available against the ECs, resulting in a continuous increase in their concentration. Non-thermal plasma, as an advanced oxidation process, has been emerging as a promising technology against the ECs treatment. In the present work, a detailed experimental study is carried out to evaluate the efficacy of a non-thermal plasma jet with two dyes, Rhodamine B and Methylene Blue, as model contaminants. The plasma jet provided a complete dye decoloration in 30 min with an applied voltage of 6.5 kV. .OH, having the highest oxidation potential, acts as the main reactive species, which with direct action on contaminants also acts indirectly by getting converted into H2O2 and O3. Further, the effect of critical operational parameters viz., sample pH, applied voltage (4.5-6.5 kV), conductivity (5-20 mScm-1), and sample distance on plasma treatment efficacy was also examined. Out of all the assessed parameters, the applied voltage and sample conductivity was found to be the most significant operating parameter. A high voltage and low conductivity were found to favor the dye decoloration, while the pH effect was not that significant. To understand the influence of plasma discharge gas on treatment efficacy, all the experiments are conducted with Argon and Helium gases under the fixed geometrical configuration. Both the gases provided a similar dye decoloration efficiency. The DBD plasma system with complete dye removal also rendered maximum mineralization of 73 % for Rd. B, and 60 % for Met. Blue. Finally, the system's efficiency against the actual ECs (four pharmaceutical compounds, viz., metformin, atenolol, acetaminophen, and ranitidine) and microbial contaminant (Escherichia coli) was also tested.Comment: 23 pages, 7 figure

A solar powered handheld plasma source for microbial decontamination applications

A fully portable atmospheric pressure air plasma system is reported to be suitable for the microbial decontamination of both surfaces and liquids. The device operates in quiescent air, and includes an integrated battery which is charged from a solar cell and weighs less than 750 g, making it highly amenable for a wide variety of applications beyond the laboratory. Using particle imaging velocimetry to visualise air flows around the device, the geometric configuration of the plasma generating electrodes was enhanced to induce a gas flow on the order of 0.5 m s-1 directed towards a sample placed downstream, thus improving the transport of plasma generated reactive species to the sample. The microbial decontamination efficiency of the system was assessed using potable water samples inoculated with common waterborne organisms Escherichia coli and Pseudomonas fluorescens. The reduction in the number of microorganisms was found to be in the range of 2-8 log and was strongly dependent on the plasma generation conditions