Study of Atmospheric Microplasma for Plasma-Life Science

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Study of Atmospheric Microplasma for Plasma-Life Science Kazuo Shimizu, Shigeki Tatematsu, Hodaka Fukunaga and Marius Blajan Innovation and Joint Research Center, Shizuoka University, 3-5-1, Johoku, Hamamatsu, Japan ABSTRACT Atmospheric microplasma has been intensively studied for various application fields, since this technology has features shown here: generated around only 1 kV under atmospheric pressure, discharge gap of only 10 to 100 μm, dielectric barrier discharge. Low discharge voltage atmospheric plasma process is an economical and effective solution for various applications such as indoor air control including sterilization, odor removal, surface treatment, and would be suitable for plasma-life science field such as medical application. In this paper, the basic study for plasma-life science will be presented. One life science application of microplasma is “sterilization”. The sterilization process was carried out with active species generated between the microplasma electrodes. The active species were observed by emission spectrometry. The spectra showed the existence of active species, and the microplasma had typical characteristics of non-thermal plasma. Sterilization of E. coli was confirmed after microplasma treatment with Ar gas. The bacteria shape was changed after the microplasma process. The other application is “Surface treatment” by long life active species of materials which used for the medical field. The targets are glass, polymer film and others could be also possible. The process is known as remote microplasma sterilization method. Microplasma generated by both air and Ar are effective for sterilization. Observation by the SEM images shows the E. coli had a shrunked shape after the microplasma treatment. The contact angle of a water droplet on the polymer surface was measured to estimate its hydrophilicity. The relation between the contact angle and treatment time was investigated. Contact angle decreased from 75.6° to 45.6° after 10 s of treatment. INTRODUCTION Non-thermal plasma proved to be a more economical and ecological replacement of conventional technologies for various applications such as sterilization [1], cancer cell control [2] or wide range of biomedical applications [3]. Research on animal and human living tissue sterilization using floating-electrode dielectric barrier discharge [4] or treatment of human liver cancer cell by micro jet plasma [5] showed that non-thermal plasma could be applied for the treatment of living tissues. The effects are attributed to both production of beneficial radicals which intersect with biological reaction chains and to the surface and intracellular generation of electric fields [6]. Microplasma has advantages over other types of non-thermal plasma. Atmospheric microplasma can be generated at atmospheric pressure at only around 1.0 kV, since its discharge gap is in the order of micro-meters. It is not necessary a vacuum enclosure therefore it is small device. Our microplasma, which is generated between parallel plate electrodes, can treat a wid