Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session FT1: Biological and Biomedical Applications of Plasmas I |
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Chair: Gerrit Kroesen, Eindhoven University of Technology Room: Amphitheatre 204 |
Tuesday, October 23, 2012 3:30PM - 3:45PM |
FT1.00001: Plasma Filaments in Dielectric Barrier Discharges Penetrating into High Aspect Ratio Cracks for Sterilization Natalia Yu. Babaeva, Mark J. Kushner The ability of surface-hugging-plasmas, as produced in dielectric barrier discharges (DBDs), to penetrate into crevices, turn corners and navigate geometrical obstructions, is important in plasma-wound healing and sterilization. In this talk, we discuss results from a computational investigation of the plasma filaments produced in an air DBD and impinging on and penetrating into deep, high aspect ratio cracks in the bottom dielectric. The model used in this work, \textit{nonPDPSIM}, is a plasma hydrodynamics model in which continuity, momentum and energy equations are solved for charged and neutral species with solution of Poisson's equation for the electric potential, concurrent with radiation transport. A Monte Carlo simulation is used to obtain ion energy distributions (IEDs) to surfaces. Cracks are 1 mm deep and 3 $\mu $m to 250 $\mu $m wide (aspect ratios of 333 to 4). We found that when impinging onto the cracked dielectric, the plasma filament conformally spreads over the surface. The conductive plasma transfers the applied potential to the opening of the crack. The width of the crack, $w$, then determines the penetration of the plasma. If $w$ is large compared to the filament, the penetration is surface hugging. If $w$ is commensurate with the filament, the plasma fills the crack. If the Debye length is about $w$ or larger, there is not significant penetration. For the conditions investigated, penetration occurred for $w >$ 5-6 $\mu $m. IEDs onto the surfaces of the trenches produce transient pulses of ions with energies $>$150 eV. [Preview Abstract] |
Tuesday, October 23, 2012 3:45PM - 4:00PM |
FT1.00002: Calculation of Ion Energy Distribution Functions at the Inner Surface of a Pet Bottle During Sterilization Processes Daniel Szeremley, Simon Steves, Ralf Peter Brinkmann, Peter Awakowicz, Mark J. Kushner, Thomas Mussenbrock Due to a growing demand for bottles made of polyethylene terephthalate (PET) fast and efficient sterilization processes as well as barrier coating to decrease gas permeation are required. Plasma sterilization is an alternative way of sterilizing PET without using toxic ingredients (e.g. hydrogen peroxide or peracetic acid). To allow investigations in the field of plasma sterilization of PET bottles, a microwave plasma reactor has been developed. A coaxial waveguide combined with a gas-inlet, a modified plasmaline, is used for both coupling the microwave power and injecting the gas mixture into the bottle. One key parameter in the context of plasma treatment of bottles is the ion energy distribution function (IEDF) at the inner surface of the bottle. Additional it is possible to apply a DC bias potential to a metal cage which is placed around the bottle. Numerical results for IEDFs performed by means of the Hybrid Plasma Equipment Model (HPEM) are presented. Plasmas with relevant gas mixtures (Ar and ArO$_2$) at different pressures and input powers are examined. The numerical results are compared with experimentally obtained data and show very good agreement. [Preview Abstract] |
Tuesday, October 23, 2012 4:00PM - 4:15PM |
FT1.00003: Optimizing Pulse Waveforms in Plasma Jets for Reactive Oxygen Species (ROS) Production Seth Norberg, Natalia Yu. Babaeva, Mark J. Kushner Reactive oxygen species (ROS) are desired in numerous applications from the destruction of harmful proteins and bacteria for sterilization in the medical field to taking advantage of the metastable characteristics of O$_{2}(^{1}\Delta )$ to transfer energy to other species. Advances in atmospheric pressure plasma jets in recent years show the possibility of using this application as a source of reactive oxygen species. In this paper, we report on results from a computational investigation of atmospheric pressure plasma jets in a dielectric barrier discharge (DBD) configuration. The computer model used in this study, \textit{nonPDPSIM}, solves transport equations for charged and neutral species, Poisson's equation for the electric potential, the electron energy conservation equation for the electron temperature, and Navier-Stokes equations for the neutral gas flow. A Monte Carlo simulation is used to track sheath accelerated secondary electrons emitted from surfaces and the energy of ions incident onto surfaces. Rate coefficients and transport coefficients for the bulk plasma are obtained from local solutions of Boltzmann's equation for the electron energy distribution. Radiation transport is addressed using a Green's function approach. Various waveforms for the voltage source were examined in analogy to spiker-sustainer systems used at lower gas pressures. [Preview Abstract] |
Tuesday, October 23, 2012 4:15PM - 4:30PM |
FT1.00004: Plasma-generated reactive oxygen species for biomedical applications J.S. Sousa, M.U. Hammer, J. Winter, H. Tresp, M. Duennbier, S. Iseni, V. Martin, V. Puech, K.D. Weltmann, S. Reuter To get a better insight into the effects of reactive oxygen species (ROS) on cellular components, fundamental studies are essential to determine the nature and concentration of plasma-generated ROS, and the chemistry induced in biological liquids by those ROS. In this context, we have measured the absolute density of the main ROS created in three different atmospheric pressure plasma sources: two geometrically distinct RF-driven microplasma jets ($\mu $-APPJ [1] and kinpen [2]), and an array of microcathode sustained discharges [3]. Optical diagnostics of the plasma volumes and effluent regions have been performed: UV absorption for O$_{3}$ and IR emission for O$_{2}$(a$^{1}\Delta )$ [4]. High concentrations of both ROS have been obtained (10$^{14}$--10$^{17}$cm$^{-3})$. The effect of different parameters, such as gas flows and mixtures and power coupled to the plasmas, has been studied. For plasma biomedicine, the determination of the reactive species present in plasma-treated liquids is of great importance. In this work, we focused on the measurement of the concentration of H$_{2}$O$_{2}$ and NO$_{X}$ radicals, generated in physiological solutions like NaCl and PBS.\\[4pt] [1] N. Knake et al., J. Phys. D: App. Phys. \textbf{41}, 194006 (2008)\\[0pt] [2] K.D. Weltmann et al., Pure Appl. Chem. \textbf{82}, 1223 (2010)\\[0pt] [3] J.S. Sousa et al., Appl. Phys. Lett. \textbf{97}, 141502 (2010)\\[0pt] [4] J.S. Sousa et al., Appl. Phys. Lett. \textbf{93}, 011502 (2008) [Preview Abstract] |
Tuesday, October 23, 2012 4:30PM - 4:45PM |
FT1.00005: Atomic nitrogen measurements in a radio-frequency atmospheric-pressure plasma jet Erik Wagenaars, Timo Gans, Deborah O'Connell, Kari Niemi Atmospheric-pressure plasma jets (APPJs) driven with radio-frequency voltages have the potential to be used in a range of new healthcare applications. To guarantee the safety and effectiveness of these new devices, a thorough understanding of the physics and chemistry of these plasmas is needed. The exact mechanisms through which APPJs affect biological materials like cells, bacteria and DNA are largely unknown, however, recent studies suggest the importance of reactive oxygen and nitrogen species (RONS). The starting point for the creation of many of the different RONS is the production of atomic oxygen and nitrogen in APPJs by breaking up oxygen and nitrogen gas molecules. In order to fully understand and control the production and effects of different RONS it is therforte important to measure atomic oxygen and nitrogen species in APPJs. This contribution presents the first direct measurements of atomic nitrogen species in APPJs. The measurements were performed with a two-photon absorption laser-induced fluorescence diagnostic, using 206.65 nm laser photons for the excitation of ground-state N atoms and observing fluorescence light around 744 nm. The APPJ was run with a helium gas flow of 1 slm and varying small admixtures of molecular nitrogen of 0 -- 0.7 vol{\%}. A maximum in the measured N concentration was observed for an admixture of 0.25 vol{\%} nitrogen gas. [Preview Abstract] |
Tuesday, October 23, 2012 4:45PM - 5:00PM |
FT1.00006: Diagnostic of the surface micro-discharge using spectroscopic methods Yang-Fang Li, Gregor Morfill A handheld and battery-driven CAP device is designed for clinical studies. The accomplished medical phase I study has shown high bactericidal efficacy \textit{in vitro}, \textit{ex vivo} as well as \textit{in vivo}. Although tests have been done concerning the biological safety and toxic gas emissions accordingly to the electrical safety, the chemical production of this device is not well addressed. In particular, the ozone production remains to be a big issue for safety reasons and reactive Nitrogen and Oxygen species (RNOS) are regarded to the key players for the biological and medical effects of CAPs. Given the application time for the clinical trial would be in the range of 30 seconds, we will present the temporal evolution of several RNOS within running time of a few minutes. The measurement is done mainly by the optical emission and absorption spectroscopies. Depending on the characteristic parameters of the applied voltage signal for discharge, the production of the RNOS may evolve in different profiles. Especially for high power operation, the discharge takes around 30 seconds to reach a steady state. Although the discharge power is found to be the most important factor, the characteristic frequency and even the gas temperature in ambient air, which in our case is the working gas, may alter the yields of several species, for example ozone and atomic Oxygen. The result will help for developing CAP devices for different applications and to design the protocol for the clinical test concerning the efficacy and safety. [Preview Abstract] |
Tuesday, October 23, 2012 5:00PM - 5:15PM |
FT1.00007: Transfer of Atmospheric Pressure Plasma Streams Across Dielectric Tubes and Channels Zhongmin Xiong, Eric Robert, Vanessa Sarron, Jean-Michel Pouvesle, Mark J. Kushner Transfer of atmospheric pressure plasma streams refers to the production of an ionization wave (IW) in a tube or channel by impingement of a separately produced IW onto its outer surface. In this paper, we report on a joint numerical and experimental investigation of this plasma transfer phenomenon. The two tubes, source and transfer, are perpendicular to each other in ambient air with a 4 mm separation. Both are flushed with Ne. The primary IW is generated in the source tube by ns to $\mu $s pulses of $\pm$25kV, while the transfer tube is electrodeless, not electrically connected to the first and is at a floating potential. The simulations are conducted with \textit{nonPDPSIM}, a 2-dimensional plasma hydrodynamics model with radiation transport. In this model, the 3-d tubes in the experiments are represented by 2-d capillary channels. The experimental diagnostics include ns resolution ICCD imaging. Simulations and experiments show that the primary IW propagates across the inter-tube gap and, upon impingement, induces two secondary IWs propagating in the opposite directions in the transfer tube. Depending on the polarity of the primary IW and the rate of rise (dV/dt) of the voltage pulse, the secondary IWs can have polarities either the same or opposite to that of the primary IW. [Preview Abstract] |
Tuesday, October 23, 2012 5:15PM - 5:30PM |
FT1.00008: Long and Highly Flexible Micro-Plasma Jet Device for Endoscopic Treatments Jae Young Kim, Daniel Cutshall, Thomas Hawkins, John Ballato, Sung-O Kim A long and highly flexible micro-plasma jet device made of hollow-core optical fiber has been proposed for use in endoscopic treatment. The fiber which is used has an inner diameter of 350 $\mu $m and an outer diameter of 700 $\mu $m. The plasma jet device was 165 cm in length and merely 2 millimeters wide at the widest point. The system was configured so that thin wire electrodes were isolated inside of the optical fibers, thereby not allowing contact with the environment at the end of the device where the jet is produced. Such an electrode arrangement allows for great safety while also producing a stable plasma column and jet during treatment inside the patient's body. Despite the small inner diameter and the low gas flow rate, the generated plasma jets are shown to be stable and sufficiently effective at treating cells or germs. The exceptional flexibility and length of the micro-plasma device will enable it to reach diverse areas inside the human body. Plasma devices analogous to the one created have enormous potential for the treatment of a myriad of internal human ailments due to the devices' great flexibility and favorable chemical, medical, and physical properties. [Preview Abstract] |
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