Junggil Kim

Endodontic plasma-jets for root-canal disinfection

Summary form only given. A plasma treatment for root-canal disinfection is expected to be substituted for the traditional methods for which some toxic antibacterial compounds such as sodium hypochlorite (NaOCl), chlor-hexidine (CHX), and others have been used with a tool of endodontic file (NiTi). Sometimes the toxic compound brings about the serious side-effects as a dropsical swelling around the root of a tooth, a massive swelling of the check, and an ecchymosis and a bruise on the side of face. A high attention should be paid to the perform irrigation as well as to apply a medicament for such a narrow, deep, and irregular-shaped root canals. Atmospheric pressure plasma jet possibly generates lots of reactive species comparable to conventional chemicals. Furthermore the treatment area can be focused narrowly and deeply without making sever toxic residues. For the last decade, a lot of jet-devices have been introduced and there have been some preliminary attempts to use a plasma-jet in endodontic practice but the completely sterilized results have not been reported yet.The purpose of this research is to develop an efficient device of a plasma jet system for dental surgery. We introduce a new concept of the jet-system combined with a dielectric barrier discharge, whose properties are as follows: (i) An Ar-jet device is operated by a remarkably low voltage with a sinusoidal frequency of several tens of kHz. Even in an air-jet device, the same electrode structure has been involved as that of an Ar-jet. (ii) To overcome the difficulty of approaching the deep and narrow irregular-cavity of rootcanal, a reliable and user-friendly plasma-jet device is needed. Our system is equipped with a proper structure of a hooked nozzle through which the plasma can be generated inside the canal. To prevent the infection during the operation, a disposable single-usage of the nozzle system is developed. (iii) Optical spectrum is analyzed to compare this jet-system to the conventional jets and to verify the effective radicals in killing bacteria. And finally, a bactericidal effect of this plasma jet on the Streptococcus mutants and Enterococcus faecalis as main pathogens in a root-canal is investigated in variously-designed 3-dimensional tooth model made by 3D printer or in extracted tooth.

Propagation of plasma diffusion waves in various plasma discharge columns

Summary form only given. The plasma bullet has been explained with the model of streamer propagation in many reports. The streamer theory of ionization wave for plasma plume/bullet might not be enough for proper explanation. The streamer discharge is represented in general to be the random channeling behavior in a wide open space where the discharge path is not restricted. For instances, the discharge of transient state or quasi-steady state must be a streamer discharge in the atmospheric discharge with a sharp needle electrode or with a plane electrode like a dielectric barrier discharge (DBD). However, the plasma jet seems to be a steady state when the discharge path is defined by the glass tube through which the discharge gas is blowing. Therefore, the discharge of plasma jet accompanied with the glass tube seems not to be explained only with the streamer discharge but it must be a normal glow, since the discharge of plasma jet is guided by the flow of inert gas as well as by the discharge route of glass tube or other structures. In this study the electrostatic plasma diffusion waves driven by a plasma density gradient are described to verify the propagation of light signals observed in the discharge experiments such as long discharge tubes, plasma jets, and plasma display panels. Plasma diffusion waves, electron waves and ion waves, propagate together with the group velocity of the wave-packet as ug≈cs2/un, with the acoustic velocity cs and the plasma diffusion velocity un. The propagation phenomena are explained in terms of the plasma density gradient associated with discharge parameters such as the plasma scale, the plasma current, and the electric field strength. The evidence of plasma diffusion wave is shown in the observation results of optical signals providing the information of plasma behavior in the atmospheric plasma jet. In a plasma column between a high-voltage electrode and the virtual ground of infinite open air, the velocity is varied at each area as it is about 104 m/s inside the glass tube, it becomes fast as 105 m/s at the plasma plume exiting the glass tube, and it is slow down to the open air. If the variation of optical intensity corresponds to the plasma density, the propagation velocity could be understood with the density gradient of the plasma. In the optical signals observed in the plasma jets, two types of waves are analyzed. One is a traveling wave along the forward direction of plasma density gradient from high voltage side to the ground electrode. The other is a backward wave from the backward direction of plasma density gradient and a reflecting wave from the ground electrode.

Electric potential measurement of the plasma plume in atmospheric-plasma jet

Summary form only given. The electric potential along a long plasma column formulated inside the fine tube of glass or Teflon is measured by a high voltage probe.1 An atmospheric plasma is generated into the fine tubes by a syringe electrode through which the gas is blown. The plasma jet is operated by the DC-AC inverter with a several tens of kHz. At the position of plasma column extended from the electrode applied by high-voltage, the plasma potential is measured to be high near the high voltage side while the potential decreases as the location becomes farther away from the high voltage electrode. If it is grounded at the end of glass tube, the plasma column voltage is measured to be about 0 V near the ground.

Doping of crystalline silicon solar cell by making use of atmospheric and sub-atmospheric plasma jet

Summary form only given. The doping process in the manufacturing of solar cell is to form a p-n junction by the injection of impurity materials into a silicon wafer. The elements of III or V group are used in the doping process during which the dopant materials are diffused thermally into the doping layer. In the conventional process of doping, the furnace or the laser is used with the control of temperature in the doping equipment.

Dielectric barrier atmospheric discharge combined with petri-dish

A plasma generating apparatus of a low-frequency dielectric barrier discharge (DBD) is designed and applied to treating microorganisms.

Spatiotemporal behavior of excited Xe atom density in the 1 s5 metastable state according to the Xe mole fractions in He-Ne-Xe ternary gas mixtures at alternating current plasma display panel(AC-PDP)

Summary form only given. We have measured the excited Xe atom density in the ls5 metastable state in accordance with Xe mole fraction to He and Ne in alternating current plasma display panels by laser absorption spectroscopy. The various test panels with Xe mole fractions of 4, 7, 10 and 15 % to He-Ne have been used in this experiment. The 4 inch test panels with discharge cell of T-typed indium-tin-oxide electrode with closed barrier rib have been used and driven by the same driving conditions in this experiment. It is noted that the correlation between the excited Xe atom density in the ls5 metastable state and the VUV luminous efficiency is in good agreement at xenon mole fraction from 1% to 15% with each other.