AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuP

Paper PS-TuP12
Diagnostic Study of Microplasmas in Contact with Saline Solution

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Plasma Science and Technology Poster Session
Presenter: A.H. Hsieh, National Taiwan University, Taiwan
Authors: H.W. Chang, National Taiwan University, Taiwan
A.H. Hsieh, National Taiwan University, Taiwan
C.L. Chen, National Taiwan University, Taiwan
C.C. Hsu, National Taiwan University, Taiwan
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Microplasmas in contact with saline solution are studied. This microplasma is sustained using a DC power source with the output voltage up to 600 V and the current up to 1.5 A. The powered electrode is the electrode at which the plasma forms. It consists of a thin platinum wire ( 0.5 mm in diameter) covered by a glass tube except the 2-mm near-tip area. The grounding electrode is a 1 cm * 3 cm- and 0.5-mm-thick stainless steel sheet plate. Both electrodes are immersed in saline solution of various concentrations. The powered electrode serves either as the anode or the cathode, depending upon the operating condition chosen. Diagnostic tools used in this work include a voltage probe and a current probe to monitor the voltage and the current waveforms at the electrode, respectively; an optical emission spectrometer was used to monitor the time-averaged emission spectra. It is shown that the microplasma in 1 M saline solution can be ignited without difficulty for the voltages above 300 V. The forming and sustaining of the microplasma have been found to be a complicated phenomenon associated with the bubble formation and the plasma ignition in the bubbles. As the powered electrode is positively powered (i.e. the anode), two discharge modes, high and low current modes, have been identified. In the low current mode, the microplasma appears to be more stable, and the bubble stays and attaches at the tip of the powered electrode steadily for many seconds, while in the high current mode, the bubbles continuously forms and detaches from the electrode. The major optical emission lines in the high current mode are Na (589 nm) and H (656 nm) emissions. In this presentation, the potential use of this microplasma for materials processing will be discussed.