
doi: 10.5772/13192
Plasmas are partially ionized gases and are described as the “fourth state” of matter. Irving Langmuir coined the word ‘plasma’, in 1928, for the ionized gas in which electrons, ions, and excited particles are suspended similar to the cells suspended in the blood plasma. Naturally-existing plasma includes the sun and the stars, lightening, polar lights, etc. Artificially-produced plasmas are fluorescent lamps, neon signs, plasma displays and monitors, etc. Much more applications of plasma have been made possible in the recent decades. There are several methods for plasma generation. One among them is by applying sufficient electric field in different gas mixtures confined in a low-pressure chamber. Such lowpressure plasmas are suitable for tailoring the surface properties of different materials, for film deposition, for sterilization of non-living matter, etc. However, treatment of pressuresensitive objects and materials is not possible using a low-pressure system. Treatment of living tissues, as in the case of medical treatment, is possible only with plasma devices which operate at atmospheric pressure. Because of high pressure, discharge ignition at atmospheric conditions requires high voltage and can arouse high current density. The gas temperature in active plasma volume increases up to several thousand degrees. By such treatment, the living object is over heated (hyperthermia) and partially evaporated. Such plasma sources are used in surgery as plasma scalpel and blood coagulator (Stoffels, 2007). For gentle treatment of living object at atmospheric pressure conditions, limitation of current flowing through the treated object is necessary. This can be achieved by placing the object slightly away from the active plasma volume as in the case of “indirect” plasma treatment. The other ways are short voltage pulsing (Ayan, 2008 & Walsh, 2008) and using a dielectric barrier (otherwise called ‘insulator’) that drastically reduces electric current through the treated object. Devices using the latter are so-called “dielectric barrier discharges (DBD)” which are useful for “direct” treatment of living object which comes in immediate contact with the plasma.
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