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Pohang, South Korea

Kim H.Y.,Pohang University of Science and Technology | Lee H.W.,MediPL Corporation | Kang S.K.,Pohang University of Science and Technology | Lee H.W.,Pohang University of Science and Technology | And 4 more authors.
Physics of Plasmas | Year: 2012

Low temperature atmospheric pressure plasmas have been known to be effective for living cell inactivation in a liquid solution but it is not clear yet which species are key factors for the cell treatment. Using a global model, we elucidate the processes through which pH level in the solution is changed from neutral to acidic after plasma exposure and key components with pH and air variation. First, pH level in a liquid solution is changed by He+and He(21S) radicals. Second, O3density decreases as pH level in the solution decreases and air concentration decreases. It can be a method of removing O3that causes chest pain and damages lung tissue when the density is very high. H2O2, HO2, and NO radicals are found to be key factors for cell inactivation in the solution with pH and air variation. © 2012 American Institute of Physics.


Kang S.K.,Pohang University of Science and Technology | Seo Y.S.,MediPL Corporation | Lee H.W.,Pohang University of Science and Technology | Aman-Ur-Rehman,Pohang University of Science and Technology | And 4 more authors.
Journal of Physics D: Applied Physics | Year: 2011

A new type of microwave-excited atmospheric pressure plasma source, based on the principle of parallel plate transmission line resonator, is developed for the treatment of large areas in biomedical applications such as skin treatment and wound healing. A stable plasma of 20 mm width is sustained by a small microwave power source operated at a frequency of 700 MHz and a gas flow rate of 0.9 slm. Plasma impedance and plasma density of this plasma source are estimated by fitting the calculated reflection coefficient to the measured one. The estimated plasma impedance shows a decreasing trend while estimated plasma density shows an increasing trend with the increase in the input power. Plasma uniformity is confirmed by temperature and optical emission distribution measurements. Plasma temperature is sustained at less than 40 °C and abundant amounts of reactive species, which are important agents for bacteria inactivation, are detected over the entire plasma region. Large area treatment ability of this newly developed device is verified through bacteria inactivation experiment using E. coli. Sterilization experiment shows a large bacterial killing mark of 25 mm for a plasma treatment time of 10 s. © 2011 IOP Publishing Ltd.


Kang S.K.,MediPL Corporation | Kim H.Y.,Pohang University of Science and Technology | Yun G.S.,Pohang University of Science and Technology | Lee J.K.,MediPL Corporation | Lee J.K.,Pohang University of Science and Technology
Plasma Sources Science and Technology | Year: 2015

A portable microwave air plasma has been developed for safe and effective wound healing. The device is operated by a fixed microwave power and two different air gas flows (main and cooling air flow). It was found that the speeds of the two air flows determine the stability of the plasma jet and gas temperature and thereby regulate the concentrations of the individual reactive species. Two different regimes, i.e. the NO abundant (0.1 slm main air flow) and ozone abundant regimes (4 slm main air flow), were identified as suitable for wound healing without thermal damage and toxicity. These regimes show similar plasma characteristics (e.g. less than 40°C at the treatment point, less than 4 ppm of NO2) except for different NO and ozone amounts. Both regimes show more than twice as fast wound healing speed compared with the untreated case without any histological damages. Faster healing speed with intrinsic ozone safety make the NO abundant regime the best operation regime for wound healing. Finally, the stability of the developed device was demonstrated by a one-hour continuous operation test with a 24 V battery. © 2015 IOP Publishing Ltd.


Lee H.W.,Pohang University of Science and Technology | Kang S.K.,Pohang University of Science and Technology | Kwon S.K.,Pohang University of Science and Technology | Won I.H.,Pohang University of Science and Technology | And 4 more authors.
Digest of Technical Papers-IEEE International Pulsed Power Conference | Year: 2013

Pulse modulation technique was applied for microwave excited atmospheric pressure air and Ar plasmas with fixed average power. Breakdown and sustain powers were measured and UV-Vis emission spectra were observed. As the duty ratio decreased, pulse modulated plasmas showed enhanced results as compared to continuous signal excited plasmas. Breakdown powers of both of air and Ar plasmas were reduced as duty ratio decreased. Reactive species including hydroxyl radicals, atomic oxygen and nitric oxide were increased with the decrease of duty ratio. The change of breakdown power and increase of reactive species give advantages for biomedical applications. Gas temperature was reduced also in both of air and Ar plasmas with the decrease of duty ratio. The results related to the high energy electrons which were generated during on-time of the microwave signal. Blood coagulation experiment of the air plasma was conducted and it showed ∼7 times faster coagulation than natural coagulation. © 2013 IEEE.


Lee M.U.,Pohang University of Science and Technology | Jeong S.Y.,Pohang University of Science and Technology | Won I.H.,Pohang University of Science and Technology | Sung S.K.,MediPL Corporation | And 3 more authors.
Physics of Plasmas | Year: 2016

Particle-in-cell/Monte Carlo simulations and numerical analysis of a single particle motion are performed for atmospheric He microplasmas at microwave frequencies to determine the characteristics of non-Maxwellian to Maxwellian transition. The left and the right regimes of Paschen curve, divided by this transition, reveal that the transition frequencies depend on the gap of electrodes and the neutral gas pressure to follow scaling laws for a new extended Paschen law. The fluid models are reasonable at the right-side regime of Paschen breakdown areas, but not on the left side, which is highly kinetic for electrons. The plasmas driven by weaker electric fields of high enough frequencies at the right-side Paschen regime breed more energetic electrons. © 2016 Author(s).

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