a b s t r a c tCold atmospheric plasma treatment of microorganisms and living tissues has become a popular topic in modern plasma physics and in medical science. The plasma is capable of bacterial inactivation and noninflammatory tissue modification, which makes it an attractive tool for treatment of skin diseases, open injuries and dental caries. Because of their enhanced plasma chemistry, Dielectric Barrier Discharges (DBDs) have been widely investigated for some emerging applications such as biological and chemical decontamination of media at ambient conditions. Despite the high breakdown voltage in air at atmospheric pressure, the average current of DBD discharges is low. Therefore, a DBD can be applied in direct contact with biological objects without causing any damage. In this work a 60 Hz DBD reactor, which generates cold atmospheric plasma inside Petri dishes with bacterial culture, is investigated. Samples of Staphylococcus aureus, a Gram-positive bacterium and Escherichia coli a Gram-negative bacterium were selected for this study. The bacterial suspensions were evenly spread on agar media planted in Petri dishes. The reactor electrodes were placed outside the Petri dish, thus eliminating the risk of samples microbial contamination. The covered Petri dish with agar medium in it serves as dielectric barrier during the treatment. The plasma processing was conducted at same discharge power (∼ 1.0 W) with different exposure time. Sterilization of E. coli and S. aureus was achieved for less than 20 min. Plasma induced structural damages of bacteria were investigated by Scanning Electron Microscopy.

This work reports the development of atmospheric pressure plasma reactor with dielectric barrier discharge DBD for material treatment. The DBD discharge has been generated in planar geometry reactor powered by ac voltage provided by conventional high voltage transformer. The dielectric barrier consisted of two glass slabs, which cover both reactor electrodes. The air discharge gap between the dielectric layers was varied from 1.0 to 3.0mm. The power consumption of the DBD reactor was evaluated by the Lissajous figures method. The optimization of reactor geometry for material processing is discussed.

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In this study sulphur hexafluoride (SF 6 ) plasmas and argon plasma immersion ion implantation (ArPIII) techniques have been applied to improve the hydrophobicity of poly(tetrafluoroethylene) (PTFE), polyurethane and silicone surfaces. As evaluated by water contact angle measurements, all the treatments resulted in a significant enhancement in the hydrophobicity of the polymers. However, exposure of the treated samples to air induced a strong variation in their hydrophobicity as a consequence of post-plasma reactions between atmospheric species and remnant surface free radicals. X-ray photoelectron spectroscopy results strongly suggest that for polyurethane and silicone the surface fluorination by SF 6 plasmas and the creation of new carbon bonds and radicals are the main agents for hydrophobicity enhancement. The PTFE exposed to ArPIII revealed increases in the contact angles after exposure to air. A significant incorporation of oxygen and the formation of new carbon bonds were revealed by XPS measurements.