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In this paper, a low-cost and portable plasma device is developed to generate atmospheric pressure nonthermal air plasma jet for safe and effective biomedical applications. The device mainly consists of a pen electrode, a high-frequency ac power supply, an ac/dc module, and a dc air pump, and it totally costs only U.S. $63 and has a small size of 280 mm $\times190$ mm $\times180$ mm. The appearance of two-mode discharge of half-wave and full-wave breakdown with the changing of applied voltage is identified, and the length of the plasma jet is optimized through studying on the influences of distance between two electrodes, gas flow rates, and hole diameters of the gas outflow in ground electrode. Stronger plasma with a longer jet length of 12 mm can be obtained in the full-wave breakdown discharge mode, while moderate plasma with a length of 8 mm can be obtained in the half-wave breakdown discharge mode. The discharge characteristics of the device such as the main generated active particle, voltage and current, discharge power, and operation temperature are obtained. It is shown that rich active species for biomedical application can be generated at low power of approximate 2 W and low operation temperature of approximate 40 °C. The developed device is tested for biomedical application, and the results of effective sterilization of C. albicans and blood coagulation are obtained. [ABSTRACT FROM AUTHOR]

Can low-temperature plasma technology play a role in medicine? This is a question that many investigators today are trying hard to give a positive answer to. It did not quite start out this way. Almost two decades ago, few "curious" electrical engineers and physicists with the help of few "brave" biologists! microbiologists asked themselves more basic questions: What happens to biological cells if they were exposed to low-temperature plasma? Will they die? Will they survive? If they survive, will they come out the same or somehow "injured"? If injured, will they be able to repair the damage and recover? What kind of damage? Which plasma agent causes the damage? etc. As will be shown in this paper, some of these fundamental questions have been partially or fully answered, but until today, a complete picture has yet to emerge. This is good and not so good. It is good because if we already knew all the answers, we would not be looking forward to a more exciting research. It is not so good because after all these years, we are still quite a ways from an implementable medical application. In this review paper, the present state of knowledge regarding the effects of cold plasma on bacteria cells (prokaryotes) and on eukaryotic cells (such as mammalian cells) will be presented. As medical applications where low-temperature plasma is showing signs of success, blood coagulation and wound healing will be described. [ABSTRACT FROM AUTHOR]

It remains a challenge to generate cold air plasma at atmospheric pressure. In this paper, a room-temperature atmospheric-pressure air plasma plume is generated by a dc power supply. Current–voltage measurements show that the discharge actually appears periodically with a frequency of about 25 kHz. The discharge current has a pulsewidth that is less than 100 ns while its peak value reaches about 17 mA. There is no risk of glow-arc transition. The plasma can be touched by a bare hand without any feeling of electrical shock or warmth. The maximum length of the plasma is about 2 cm. The whole device, including the power supply, is less than 1 kg. The preliminary inactivation experiment results show that the plasma can effectively kill Enterococcus faecalis, one of the main types of bacterium causing the failure of root canal treatment. [ABSTRACT FROM AUTHOR]

A nonequilibrium plasma flow produced uniformly in a tube was developed in this paper. The plasma was generated in polyvinyl chloride tube, 3 mm in inner diameter and 100 mm in length, between a wire electrode, 0.2 mm in diameter, and a grounded flat electrode located at the bottom of the tube. We investigated the spectrum, temperature, and ozone concentration of this plasma flow and its sterilization efficacy against Geobacillus stearothermophilus. The temperature in the tube showed uniformity along the wire electrode and increases as applied voltage was increased. With a wire electrode temperature of 337 K at a peak-to-peak applied voltage of 10 kVpp in the sine wave and a frequency of 6 kHz, sterilization of 105 cells was obtained. This result suggests the potential of the application of plasma flow rather than ethylene oxide for sterilization of the inner wall of tubes, such as catheters and artificial blood vessels. [ABSTRACT FROM AUTHOR]

In this paper, we present some results of a plasma source developed at the Plasma Laboratory of the University of Brasilia for sterilization studies at atmospheric pressure. This source was primarily conceived to produce a corona-type discharge to be used on pollutant control experiments. We used ordinary air as the precursor gas. Our apparatus consists of two coaxial cylindrical tubes with different radii connected to a high-voltage power source. We used G. stearothermophilus spores as the biological indicators. We counted the viable spores after the exposure to the plasma with the pour plate technique. Finally, we studied the biocide mechanisms of the plasma and related the inactivation of the microorganisms to plasma-induced chemical and physical processes. [ABSTRACT FROM PUBLISHER]

This paper is an essay narrating the recent history of the introduction of the biomedical applications of nonthermal plasmas to the plasma science research community. [ABSTRACT FROM AUTHOR]

It remains a challenge to generate the uniform and large-area cold plasma at atmospheric pressure. In this paper, we report a method to generate a reliable and homogeneous brush-shaped plasma plume running at atmospheric pressure. The plasma brush (110 mm in length and 10 mm in width) is mainly composed of well-aligned and hollow optical fibers. Current–voltage measurements indicate that the brush-shaped plasma plume consists of glowlike pulsed discharge with their pulsewidths of several microseconds. The generation of the \He/O2 glowlike discharge is further proved by the uniform distribution of O atoms along the transverse location of the plasma brush. This brush-shaped plasma plume is used for the application in the plasma inactivation of Candida albicans cells. About 97% of Candida albicans cells with a population of 10^5 spores are killed when exposed to the \O2/\He (volume ratio: 5/95) brush-shaped plasma plume for 150 s. Analysis indicates that plasma-activated species, such as O radicals, may play a crucial role in killing the resistant Candida albicans cells. [ABSTRACT FROM AUTHOR]

We showed that nonthermal dielectric barrier discharge (DBD) plasma compromises the integrity of the cell membrane of Deinococcus radiodurans, an extremophile organism. In samples of D. radiodurans, which were dried in a laminar flow hood, we observe that DBD plasma exposure resulted in a six-log reduction in CFU (colony-forming unit) count after 30 mm of treatment. When the Deinococcus radiodurans cells were suspended in distilled water and treated, it took only 15s to achieve a four-log reduction of CFU count. [ABSTRACT FROM AUTHOR]

A coaxial cable for microwave transmission type of atmospheric low-temperature plasma source was developed. The plasma source has the advantages of portability, simple configuration, and ability to operate with a wide range of gases and mixtures of such gases. It mainly consists of a cavity, a quartz discharge tube, a coaxial cable, a microwave power source, and a gas supply system. Using this plasma source, the authors tried to clarify its sterilization efficacy against Geobacillus stearothermophilus. A log reduction number of G. stearothermophilus of at least 5 (10-5) was obtained under the following operating conditions: gas flow rate of argon of 14 SL/min, input power is 400 W, and substrate surface temperature of 353 K. Distributions of temperature and velocities of gas were also measured two-dimensionally by using an E-type thermocouple and a Pitot tube, respectively. The temperature distributions and the peak value of temperature were found to be influenced by the gas flow rate and the kinds of gas mixtures. [ABSTRACT FROM AUTHOR]

The research and development of plasma sources, which can be used for therapeutic applications in the new and emerging field of plasma medicine, has gained more and more interest during recent years. These applications require cold nonthermal plasmas operating at atmospheric pressure. Due to the fact that, in general, plasma on or in the human body is a challenge both for medicine and plasma physics, basic research combining experimental physical and biological investigation and modeling is necessary to provide the required knowledge for therapeutic applications. It turned out that each application needs a special tailor-made plasma source, passing a minimum set of physical and biological tests before it can be considered for medical use. In addition to atmospheric-pressure plasma jets, dielectric barrier discharges offer great potential for a variety of medical indications. A new 2-D and even 3-D acting plasma source is introduced, exemplified for a possible decontamination of human extremities or similar tasks. In contradiction to most of today's existing plasma sources with fixed electrodes and nozzles, the prototype uses flexible electrodes to automatically adapt the plasma under equal and stable conditions to nearly all surface structures. First, physical and biological investigations demonstrate the general potential for therapeutic applications on preferably intact skin surfaces. [ABSTRACT FROM PUBLISHER]

Microplasma has the advantage of reducing the discharge voltage compared with other atmospheric plasmas. It is generated at atmospheric pressure at only around 1.0 kV since its discharge gap is on the order of micrometers. The experiment was performed with air and argon as the process gases, to confirm the influence of different radical species in the microplasma, on the bacteria cultures. The process gas flows through the parallel plate electrodes with holes which were covered with dielectric material and energized at about 1.0 kV. The active species generated by the dielectric-barrier discharge microplasma flows toward the exposed Escherichia coli on the agar media at a distance of 2 mm from the electrodes. The process is known as remote microplasma sterilization method. Microplasma generated by both air and Ar is effective for sterilization. Observation by the scanning-electron-microscope images shows that the E. coli had a shrunk shape after the microplasma treatment. [ABSTRACT FROM AUTHOR]

A new plasma dental probe (PDP), powered with 4-6-kV ∼100-ns electric pulses at repetition rates of up to 2 kHz, generates a room-temperature > 2-cm-long ∼2-mm-diameter plasma plume at ambient atmospheric pressure. The shape of the plasma plume depends on the gas flow rate and the pulse voltage. Growth of Bacillus atrophaeus on nutrient agar plates is completely inhibited by exposure to both He and He/(1%)O2 plasmas for 60 s. A 300-s treatment with the He/(1%)O2 plasma disinfected a human tooth root canal colonized with saliva-derived bioflims, demonstrating the potential of the PDP as a simple, safe, and effective tool or adjunct for the disinfection of root canals during endodontic therapy. He/(1%)O2 plasma is more effective than He alone for B. atrophaeus growth inhibition, and the emission spectrum of the He-O2 plasma supports the identification of atomic oxygen as the likely primary reactive chemical species contributing to bacterial inactivation. [ABSTRACT FROM AUTHOR]

Radio-frequency-driven plasma jets in argon at atmospheric pressure have been shown to emit a significant amount of UV and VUV radiation. There is an increasing interest in the use of UV and VUV photons in many fields of research and in industry, in particular for life-science applications. In order to study the antimicrobial effect of plasma-emitted UV and VUV radiation, microbiological tests and plasma diagnostics are combined. In particular, quantitative values of irradiance are estimated. The VUV emission of the plasma jet is dominated by the emission of argon excimer (Ar2). The recorded spectra between 115 and 180 nm also include several atomic emission lines of nitrogen and oxygen. The UV emissions are due to molecular bands of NO, OH, and N2. The best antimicrobial effect is observed by means of direct plasma treatment. UV and VUV emissions have a lower effect, and there is no difference observed between these two components. [ABSTRACT FROM AUTHOR]

Non-equilibrium discharge plasmas have been utilized in a variety of fields and are indispensable to material processing, nanotechnologies and biotechnologies besides conventional applications such as light sources. In this review, neutral beam etching, advanced oxidation, protein removal, combustion control and volume, non-equilibrium discharge generation at atmospheric pressure are chosen and summarized as the recent, typical applications of the non-equilibrium discharge plasmas generated from low pressure to atmospheric pressure. A brief introduction of non-equilibrium discharge plasmas is also given, which serves comprehensive understanding of the physics and chemistry behind the technology. [ABSTRACT FROM AUTHOR]

An atmospheric low-temperature plasma flow generated by a microwave discharge utilizing a coaxial cable for microwave transmission was utilized for the inactivation of a bacteria. The employed device consists of a cavity, a quartz discharge tube, a coaxial cable, a microwave power source, and a gas supply system. Using this argon plasma source, we attempted to clarify the effects of exposure temperature, exposure time, exposure distance, input power, and gas flow rate on the number of surviving cells of Escherichia coil A log reduction number of E. coil of at least 2 (10-2) was obtained at an exposure temperature of 353 K when the exposure time was 600 s with a gas flow rate of 5 Sl/min and an input power of 400 W. The number of surviving cells decreased with an increase of exposure time under any sterilization condition. [ABSTRACT FROM AUTHOR]