Gook-Hee Han

Plasma Apparatuses for Biomedical Applications

Plasma-jet systems and plasma devices of dielectric barrier discharge (DBD) are introduced for biomedical applications. To achieve the purpose of being safe and user friendly, these devices have been developed to avoid electric shock and thermal damage. These types of plasma equipment operate with a sinusoidal voltage of kilovolts at a low frequency of several tens of kilohertz. The plasma jets have been developed with the specific ground-electrode structures according to the various gases in use, such as inert gases, molecular gases, or mixture gases, and air. The Ar-plasma jet with the external ground electrode is operated in a low current of 1-2 mA with the voltage of 1-2 kV. The stable air-jet plasma/plume exiting from a small hole at the cold metal-cap nozzle of the ground electrode can be obtained in a low current of 0.5-1 mA for safety with the voltage of 5-10 kV. Both types of ground electrode, the external electrode and the metal-cap electrode, are applicable to the plasma jets of molecular or mixture gases. The devices for DBD plasmas are shown to be the new advents of plasma stamp, plasma stick, plasma comb, and plasma roller, which operate with the voltage of 2-3 kV.

Effects of reactive oxygen species on the biological, structural, and optical properties of Cordyceps pruinosa spores

Effects of reactive oxygen species (ROS) on the optical, structural, and biological properties of Cordyceps pruinosa spores were studied. Both the atmospheric pressure plasma jet (APPJ) and chemically induced ROS significantly reduced the viability of C. pruinosa spores. Changes in the peak intensity of fluorescence and the depth of the dip in the circular dichroism (CD) spectrum suggested that both the APPJ and chemical induction of ROS can cause structural alteration of the spore cell wall. Fluorescence spectra of propidium iodide-stained spores indicated that alteration of cell wall (and/or membrane) permeability is involved in the change of spore viability after plasma treatment. High-performance liquid chromatography analysis of C. pruinosa ethanol extracts showed that the APPJ and chemical induction of ROS decreased the amount of ergosterol in the spores, indicating that excessive oxidative stress destroys cellular antioxidant capacity. Absorption spectroscopy, CD spectroscopy and agarose gel electrophoresis of the DNA extracted from the plasma-treated spores showed that a decrease in the DNA content and DNA degradation can be caused by either of the two treatments. The nonthermal APPJ and chemical induction were used to generate ROS in an aqueous solution. Electron spin resonance spectra provided evidence that hydroxyl radicals and singlet oxygen exist in the plasma activated water (PAW). Overall, the decline in spore viability, in antioxidative capacity, and in DNA content can be attributed to structural alteration of the cell wall and cellular damage by reactive species originating from the APPJ and the PAW.

Plasma Propagation Speed and Electron Temperature in Slow Electron Energy Non-thermal Atmospheric Pressure Indirect-Plasma Jet

Space- and time-resolved discharge-images from a nonthermal atmospheric-pressure indirect-plasma jet have been observed using a high-speed single-frame camera to investigate the electron temperature. The propagation velocity of the indirect Ar-plasma along the plasma column has been shown to be on the order of 104 m/s, and that corresponds to an ion acoustic velocity on the order of 102 m/s. Plasma has been generated by varying input discharge voltages from 2.0 to 4.0 kV at a driving frequency of 40 kHz. Particularly, the average electron temperature in slow electron energy nonthermal atmospheric-pressure indirect-plasma jet has been found to be about 0.3 eV.

Liquid Leakage Thin Film-Tape Sensor

A liquid leakage sensor on adhesive tape with alarming function has been developed. The film sensor tape consists of three layers: a base film layer, a substrate film layer, and a protective film layer. Three conductive lines and one resistive line are printed on the substrate film layer with a nano-sized silver conductive ink by the electronic gravure printing method. The location of liquid leakage has been found to be monitored accurately by applying the pulse voltage to the conductive and resistance lines in a periodic polarity switching mode. The leakage tests for various electrolyte liquids have been performed and the accuracy of leakage error position has been achieved to be about 0.25% on 200 meter long tape length.

Wearable plasma-pads for healthcare applications: Plasma patch, plasma bandage, plasma socks, and plasma cap

Summary form only given. Wearable plasma-devices involving a dielectric barrier discharge (DBD) are introduced. The conventional devices of the atmospheric pressure plasmas, a DBD and a plasma jet developed last decades, have an inconvenient for some cases requiring a frequent treatment, a long period therapy, and a significantly large area to be exposed with the plasma. The wearable plasma-pads are provided to cover such purposes of an users description. The flexible plasma-pads are comprised by three-layers: a gauzy cloth at the base, a DBD-plasma texture-layer at the middle, and an antiseptic gauze at the top. The DBD-plasma is generated at the space between the bottom cloth and the top gauze. Many kinds of reactive species including UV penetrate through the gauzy-nets into a skin for therapy. We have two ways of texturing the plasma layer: One is to lay the insulated high voltage-wires which are widely used in the electricity. The other is to use the thin polymer-films of a polyimide film (capton film) or a poly-glass film on which the electrodes are made by pasting or printing the conducting materials. In both cases of a plasma layering a high voltage electrode and a ground electrode are formed by many ways of shapes and structures to generate the uniform plasma on the texture surface. The electric power system is also made to be wearable and portable by a rechargeable battery used in a mobile cellular phone. The high voltage is applied with a frequency of several tens of kHz, a sinusoidal voltage of a few kV in rms value through a DC-AC inverter. The plasma pads provide a various forms of products for the users purpose: such as plasma patch, plasma bandage, plasma socks, and plasma cap, etc. We have made a various size of a plasma patch of which an adhesive tape is attached around the margin. The plasma patch can stick on the face or the skin of a body like a sticking plaster for dermatology. The plasma laced-bandage is applied to a wound and a skin burn with an accident at the scene for stop bleeding and a blood coagulation to prevent the infection. The socks are worn in the night time for the treatment of a tenea-pedis. The cap is for the hair depilation and hair rejuvenation. We introduce the plasma devices relating the basic structures, the electrical properties, and the spectroscopic analysis.

Aerial ozone concentration in the pencil-type atmospheric plasma jets with the various working gases

Ozone concentration in the air is about 0.01~0.03 ppm. A perceivable concentration of ozone odor for the human nose is higher than 0.03~0.05 ppm. Therefore ozone can be easily noticeable at a low concentration so that there will not be reported the ozone poisoning accident by a long exposure to human. However, ozone has disadvantages over a toxicity to induce a chronic addiction to ozone at the level of 1~2 ppm for 2 hrs. Ozone level of 5~10 ppm could cause acute addictions such as respiratory distress, heart beat increase, and whole body paralysis.

Introduction to the proto-type plasma jets of AC, RF, and MW-discharges in Korea Plasma-Bio Research Center

The various types of atmospheric pressure plasma jets (APPJs) have been developed as the proto-type of user friend in Plasma-Bio Research Center (PBRC), Korea. According to the power sources the discharge-types are DC & a low frequency AC, RF, and micro-wave. (i) The plasma jet devices of DC-type and DBD-types have been made as the portable hand-carriers using DC-battery installed. (ii) AC-type jets with the frequency of a few tens of kHz have been developed with respect to the miniature and user-friend with the electric-safety using for the applications of human body and biology. In the proto-type device for the biomedicine applications the current is adjustable in the range from the low current of 0.1 mA to the high current of a few mAs. The inert gases or mixed gases are used. Especially, for the applications of semiconductor doping process, the single channel and the multi-channel of jet-doping systems are developed in the current range of a few or several tens of mA. (iii) RF-plasma jet is introduced with the power of 13.56 MHz. The RF power is adjustable in the range less than 100 W. The single channel of the proto-type device is shown with the discharge of inert gas for the biomedicine applications. (iv) Two-types of MW-plasma jets are developed. One is the proto-type MW-jet equipped with the miniature power source of semiconductor circuit which has been developed in this study. The frequency range is several hundreds of MHz and the power is adjustable in the range of several tens of Watt. The harmonic-tuned power amplifier of the oscillator was designed for improving drain efficiency with a single Laterally Diffused Metal Oxide Semiconductor (LDMOS) transistor using a non-linear harmonic balance simulation code. The other is the high power MW-jet system with the commercial MW-power sources. This Microwave plasma was excited at 2.45 GHz frequency and 0.8 W average power with a pulse generating width of 20μs and pulse generating period 2500μs. For the various applications this system is adjustable with respect to the peak power, the duration of pulse generation, and the pulse width of microwave.

Determination of electron-plasma temperature by measuring the propagation velocity of plasma-diffusion waves with the mixture gases of Ar-N 2 in the atmospheric pressure plasma jets

Summary form only given. From the measuring data of plasma jet propagation with ICCD camera, the determination method of the electron temperature is introduced. The bullet propagation has been analyzed by the plasma diffusion waves propagating with the group velocity of wave-packet as ug ~ cs2/un where cs is the velocity of acoustic wave and un is the velocity of plasma diffusion. The plasma-jet device is made by the syringe-needle electrode combined with the glass tube as it was introduced in [Cho G.S. et al, (2013)]. A high-voltage AC-power is supplied to the electrode of syringe needle through the ballast capacitor with the inverter of DC to AC of 40 kHz of 3.0 kV. The mixture gases of Ar and N2 are investigated with the flow late about 400 sccm. Ar-N2 Plasma Jet is one of the important issues in the applications of bio-medicine. The gases with the mixture ratio are used as: Ar(100%), Ar(98%) + Ne(2%) and Ar(95%) + Ne(5%), respectively. According to the mixture-ratio with ICCD, the group velocity of plasma propagation is observed as: 267 km/s, 305 km/s, and 313 km/s, respectively. The velocity of ion-acoustic wave is calculated to be 1.16 km/s, 1.24 km/s, and 1.25 km/s, respectively. The electron temperature is obtained as: 0.55 eV, 0.63 eV, and 0.65 eV, respectively.

Exact solution of fluid momentum equations in the atmospheric plasma-jets

Summary form only given. An exact solution of the fluid momentum equation for the incompressible steady-state flow is obtained for the gas streams inside the jet-tube and outside the tube of open air-space. In the solutions the fluid channels of gases as well as the plasmas are described with respect to the reaching distance and the expansion of gases and plasmas with the effects of particle-diffusion and gravity. In the fluid dynamics, three pressure forces are considered. The pressure force of shear stress by the flow viscosity is balanced with the pressure force of gas stream to be ejected into the air space. The other force of pressure due to the radial expansion of fluid channel reduces the velocity of fluid to be zero so that we have the reaching distance of fluid after ejecting from the nozzle. The maximum distance of gas flow with the critical Reynolds number Rnc = 2000 is calculated to be less than a hundred of nozzle-diameter for Ar, Ne, and He, respectively. Since the radial expansion of plasma is ten-times larger than that of neutral gases, the length of plasma is shorter as a few tens of nozzle-diameter. In the experiments the plasma length is verified and it increases with the increase of gas flow rate until Rn ~ Rnc and then it shrinks as the flow becomes turbulent. The variations of plasma are observed inside the jet tube and outside the tube according to the operation voltage, the flow rate. The influence of gravitation is presented on the direction of plasma spouting according to the gases, Ar, Ne, and He, respectively.

Plasma propagation speed and electron temperature of ar in atmospheric pressure non-thermal indirect bioplasma jet

Space and time resolved discharge images from an atmospheric pressure non-thermal bioplasma jet have been observed by a high-speed single-frame camera to investigate the electron temperatures. The Ar plasma propagation speed with the group velocity in the plasma column of indirect plasma jet has been shown to beabout 120 km/s which corresponding with ion acoustic velocity of 0.8 km/s of plasma exposure atan input discharge voltage various from 1.99 - 4.09 kV and driving frequency of about 40 kHz. Particularly, the electron temperature in atmospheric pressure non-thermal indirect bioplasma jet were found to be about 0.55 eV of the early part of plasma exposure, respectively. Implications of the results and directions for further studies are discussed.