« La médecine- plasma» est le domaine de recherche décrivant les applications médicales des plasmas, principalement à pression atmosphérique. Les plasmas froids sont un état de la matière caractérisé par la présence d'électrons libres ayant une énergie cinétique de plusieurs eV alors même que les ions et les neutres peuvent être à température ambiante. Cet état transitoire, hors équilibre thermique, produit des espèces chimiques très réactives. L’objectif de ce travail multidisciplinaire a été d’évaluer le potentiel anti-tumoral des plasmas-froids. Deux types de dispositifs ont été conçus et fabriqués par impression 3D: des Décharges à Barrière Diélectrique et des jets plasmas. Des études in-vitro et in-vivo ont été menées avec les lignées cellulaires TC1 et CT26. La production d’espèces réactives produites dans un liquide exposé à un plasma a été étudiée afin de comprendre les résultats in-vitro et de comparer les dispositifs plasma entre eux. Différents dispositifs à plasmas ont été réalisés afin d’étudier in-vivo, l’effet de l’énergie déposée lors du traitement sur la peau et les tumeurs. Afin de limiter l’échauffement cutané et les lésions induites un dispositif refroidi à l’azote liquide a été développé. Enfin, une simulation numérique modélisant les transferts thermiques des tumeurs et tissus sous exposition plasmas a permis de quantifier l’hyperthermie et les lésions associées en validant le modèle sur des résulats expérimentaux. Une revue critique d’études in-vivo de « médecine plasma » publiées dans la littérature est proposée afin d’évaluer le rôle de l’hyperthermie dans les effets thérapeutiques observés. / Plasma-medicine is the field of research describing the medical applications of plasmas, mainly at atmospheric pressure. Cold plasmas are a state of matter characterized by the presence of free electrons with a kinetic energy of several electron volts even though the ions and neutrals may be at room temperature. This transient state, apart from thermal equilibrium, produces highly reactive chemical species. The objective of this multidisciplinary work was to evaluate the anti-tumor potential of cold plasmas. Two types of devices have been designed and manufactured by 3D-printing: Dielectric Barrier Discharge and plasma-jets. In-vitro and in-vivo studies were conducted with TC1 and CT26 cell lines. The production of reactive species produced in a liquid exposed to plasma has been studied in order to understand the in-vitro results and to compare the plasma devices with those of other teams. Various plasma devices have been made to study the effect of the energy deposited during the in-vivo treatment of skin and subcutaneous tumors. A device cooled with liquid nitrogen has been developed to limit skin damage induced by heating. Finally, a numerical simulation modeling the heat transfers of tumors and tissues under plasmas exposure enables to quantify the hyperthermia and the associated lesions by validating the model on experimental results. A critical review of in-vivo plasma-medicine studies published in the literature is proposed to evaluate the role of hyperthermia in the therapeutic effects reported.

This dissertation proposed the idea of “plasma-enhanced chemical vapor deposition on living substrates (PECVD on living substrates)” to bridge the gap between the thin film deposition technology and the biological and living substrates. This study focuses on the establishment of the knowledge and techniques necessary to perform “PECVD on living substrates” and contains three main aspects: development, characterization, and biological applications. First, a PECVD tool which can operate in ambient air and at low temperature was developed using a helium dielectric barrier discharge jet (DBD jet). It was demonstrated that various materials, such as polymeric, metallic, and composite films, can be readily synthesized through this technique. Second, the PMMA and copper films deposited using DBD jets were characterized. High-rate (22 nm/s), low-temperature (39 ºC) PMMA deposition was achieved and the film surface morphology can be tailored by altering the discharge power. Conductive copper films with an electrical resistivity lower than 1×10-7 ohm-m were obtained through hydrogen reduction. Both PMMA and copper films can be grown on temperature-sensitive substrates, such as plastics, pork skin, and even fingernail. The electrical, optical, and imaging characterization of the DBD jets was also conducted and several new findings were reported. Multiple short-duration current pulses instead of only one broad pulse per half voltage cycle were observed when a dielectric substrate was employed. Each short-duration current pulse is induced by a leading ionization wave followed by the formation of a plasma channel. Precursor addition further changed the temporal sequence of the pulses. An increase in the power led to a mode change from a diffuse DBD jet to a concentrated one. This mode change showed significant dependence on the precursor type, tube size, and electrode configuration. These findings regarding the discharge characteristics can thus facilitate the development of DBD-jet operation strategies to improve the deposition efficacy. Finally, this technique was used to grow PMMA films onto agar to demonstrate one of its potential biological applications: sterile bandage deposition. The DBD jet with the film depositing ability enabled the surface to be not only efficiently sanitized but also protected by a coating from being reached by bacteria.

No presente estudo, um conjunto de três experimentos foram conduzidos com o objetivo de avaliar a ocorrência de Staphylococcus aureus e Listeria monocytogenes em três lacticínios (A, B e C) localizados na região sudeste do Brasil de dezembro 2013 a abril de 2015 (Experimento 1), a eficiência do tratamento com ácido peracético (APA) e jato de plasma a frio (PF) para inativar os isolados em diferentes tempos (Experimento 2) e a capacidade dos isolados produzir biofilmes na superfície de poliestireno e de aço inoxidável, juntamente com inativação e remoção de células aderidas pelo APA (Experimento 3). No Experimento 1, foram analisadas amostras de leite e queijo, superfícies com e sem contato com alimentos. L. monocytogenes foi isolada em apenas uma amostra (0,3%, N = 349) de ralo no laticínio B, enquanto seis (1,7%, n = 349) S. aureus foram isolados de luvas de manipuladores em laticínio A, salmoura no laticínio B e superfície do queijo, utensílio, bota e mão esquerda de trabalhador no lacticínio C. Apesar das incidências desses dois agentes patogênicos de origem alimentar nos lacticínios avaliados foram baixo, sua presença também indica a necessidade de controle estratégias para impedir a sua persistência e contaminação cruzada. No Experimento 2, tratamento com APA (0,5%) e jato de PF foram aplicados diretamente sobre suspensões de isolados de S. aureus e L. monocytogenes. A inativação bacteriana (aproximadamente de 7 ciclos log) foi alcançada em 120 seg. com o tratamento com APA para todos os isolados, enquanto que o tratamento com plasma a frio reduziu aproximadamente 2 ciclos log nas superficies. Outros estudos usando tratamentos de plasma a frio mais longos são necessários para a total descrição da cinética desta tecnologia para a inativação de importantes patógenos de origem alimentar. No Experimento 3, o tratamento com APA (0,5%) em diferentes tempos (0-controle, 15, 30, 60 e 120 seg.) foi avaliada para a remoção de células aderidas de quatro isolados de S. aureus e um isolado de L. monocytogenes em microplacas de poliestireno, assim como para a inativação de biofilmes dos isolados em aço inoxidável. O tratamento com APA removeu (p<0,05) células aderidas de todos os isoladoas estudados S. aureus da superfície, sem diferenças (p> 0,05) no indice de formação de biofilmes nos tempos de tratamento. No entanto, nenhum efeito (p> 0,05) foi observado em células aderidas de L. monocytogenes. A microscopia de epifluorescência mostrou que todas as bactérias testadas foram parcialmente e completamente inativadas após 15 seg e 30 seg. respectivamente. Os resultados indicam um potencial para a utilização de APA contra biofilmes formados por S. aureus e L. monocytogenes, e da necessidade de novos estudos com a PF para determinar os parâmetros ideais para a inativação dos patógenos de origem alimentar. / In the present study, a set of three experiments were conducted aiming to evaluate the occurrence of Staphylococcus aureus and Listeria monocytogenes in three dairy plants (A, B and C) from Southeast region of Brazil from December 2013 to April 2015 (Experiment 1), the efficiency of peracetic acid (PAA) and cold plasma (CP) jet treatment to inactivate the isolates at different times (Experiment 2) and the ability of the isolates to produce biofilms on polystyrene and stainless steel surface, along with inactivation and removal of biofilms by PAA (Experiment 3). In Experiment1, samples of milk and cheese, food contact surfaces and non-food contact were analyzed. L. monocytogenes was isolated in only one sample (0.3%, N=349) of drain sponge swab in dairy plant B, while 6 (1.7%, N=349) S. aureus strains were isolated from handlers\' glove in dairy plant A, brine in dairy plant B and cheese surface, cheese utensil, worker\'s boot and worker\'s left hand in dairy plant C. Although the incidences of those two food-borne pathogens in the dairy plants evaluated were low, their presence also indicates the need for control strategies to prevent their persistence and cross-contamination. In Experiment 2, PAA (0.5%) and CP jet treatment were applied directly on suspensions of S. aureus and L. monocytogenes strains. Reduction of bacterial load (nearly 7 log cycles) was achieved with 15 sec. of PAA treatment of all strains, whereas CP treatment reduced approximately 2 log cycles after 2 min. Hence, plasma treatment has a potential for reducing the bacterial load on surfaces, although further studies using longer CP treatment times are necessary to fully describe the kinetics of this technology for inactivation of important food pathogens. In Experiment 3, PAA (0.5%) treatment at different times (0-control, 15, 30, 60 and 120 sec.) was evaluated for removing of adherent cells of 4 strains of S. aureus and one strain of L. monocytogenes on polystyrene plates, as well as for inactivation of biofilms of those strains on stainless steel. PAA treatment removed (p<0.05) all the S. aureus cells from the surface, with no difference (p>0.05) in the reduction of the biofilm-forming index at the treatment times. However, no effect (p>0.05) was observed on L. monocytogenes adhered cells. Epifluorescence microscopy showed that all bacterial strains tested were partially and completely inactivated after 15 sec. and 30 sec., respectively. Results indicate a potential use of PAA against biofilms formed by S. aureus and L. monocytogenes, and the need of further studies with CP to determinate the ideal parameters for inactivation of food-borne pathogens.

Recently there has been a surge in the field of mass spectrometry centered around the concept of rapid analysis of target analytes with minimal or no sample preparation. The target analyte undergoes desorption from its surface of origin and is subsequently ionized under ambient conditions. The technique is termed ambient desorption/ionization mass spectrometry (ADI-MS). Since the introduction of ADI-MS in 2004, there has been an explosion of research based around the development of novel ambient desorption/ionization (ADI) sources with the capability of desorbing and ionizing a variety of target analytes from various sampling surfaces. One type of ADI source uses the properties of an electrical discharge, typically a helium gas plasma, for desorption and ionization. For electrical-discharge-based sources, ionization is the result of an atmospheric pressure chemical ionization (APCI) process. The initiation of the APCI process it generally attributed to the Penning ionization of atmospheric nitrogen (N2) by highly energetic helium metastable species (Hem). In this work, I describe the direct imaging of the densities of helium metastable atoms in atmospheric pressure plasma jet (APPJ) of a helium-based dielectric-barrier discharge (DBD) using collisionally-assisted laser-induced fluorescence. Axial Hem distributions are compared to the emission of excited helium (He*) and nitrogen ion (N2+*) species in the plasma. A correlation is found between Hem densities and the performance of the ionization source in ADI-MS. Fluorescence images also show that Hem densities increase substantially when a glass slide is placed 10 mm from the discharge capillary in a geometry typical for desorption/ionization experiments. Advantage is taken of the time-varying nature of the plasma to produce axial profiles of temporally and spectrally resolved fluorescence images of Hem atoms and ground state nitrogen ions in the plasma jet. The axial distribution and similarities in the temporal behavior of the helium metastable and ground state nitrogen ion species give strong evidence that nitrogen ion species are created via Penning ionization by helium metastable atoms. Although axial distributions of He*,N2+*, and N2* emission support the fluorescence data, temporally-resolved emission measurements show that emission from key plasma species is almost entirely the result of excitation by a temporal energy wave. The effect that hydrogen (H2) has on the helium metastable atom densities is also presented. The addition of hydrogen to the discharge gas severely quenches the metastable state, leaving it virtually undetectable. The addition of 0.9% H2 to the helium in the source provides an order of magnitude increase in ADI-MS signal for target analytes despite the quenching of the Hem population.

Ablation controlled electrothermal (ET) plasma discharge devices consist of a small diameter capillary through which a large amount of energy is discharged. The high energy in the discharge ablates an inner sleeve material, ionizes the material, and a high energy-density plasma jet accelerates out the open end. ET devices can find applications in internal combustion engines, Tokamak fusion fueling and stabilization, hypervelocity launchers, and propulsion. The ballistic properties of an ET device are highly dependent on the propellant and ablated material. A useful noninvasive technique to characterize a propellant in these types of devices is spectroscopy. The purpose of this study is to design and conduct experiments on the ET facility called PIPE to verify results and assumptions in the ETFLOW simulation code as well as resolve data collection issues such as equipment triggering as spectrometer saturation. Experiments are carried out using an Ocean Optics LIBS2500plus high resolution spectrometer and a Photron FASTCAM SA4 high speed camera. Electron plasma temperatures are estimated using copper peaks in the UV region with the relative line intensity method, and electron plasma density is estimated by measuring the full width at half maximum (FWHM) of the stark broadened H--β line at 486 nm. Electron temperatures between 0.19 eV and 0.49 eV, and electron densities between 4.68*1022 m-3 and 5.75*10²² m⁻³ were measured in the expanding plasma jet about an inch outside the source with values as expected for this region. Velocity measurements of PIPE match well with simulations at around 5333 m/s. This study concluded that the assumption that the propellant Lexan is completely dissociated is a valid assumption, and that the ETFLOW results for electron temperature, density, and bulk plasma velocity match experimental values. / Master of Science

Yes / Antioxidant active packaging was prepared by coating a citrus extract on the surface of polyethylene terephthalate (PET) trays which had been either treated with an atmospheric pressure plasma jet or left untreated. The surface characteristics of the packaging were examined, as were its stability and antioxidant efficacy following storage for up to 24 weeks under the following three storage conditions: room temperature, 0 % relative humidity (RH) or 50 °C. Plasma pretreatment increased coating density, thickness and roughness, and oxygenated functional groups at the polymer surface, whereas water contact angle decreased. Trays stored at room temperature did not lose their antioxidant efficacy over 24 weeks and plasma pretreatment enhanced the efficacy from week 8 onwards. Gravimetric analysis of the coating revealed a loss of antioxidant compounds only after 16 weeks. Trays stored at 0 % RH lost coating from week 1 onwards, with lower loss in plasma pretreated trays, while loss of coating was highest at 50 °C, with lower loss in plasma pretreated trays only after 24 weeks. Overall, the surface characteristics of the antioxidant active packaging were modified by plasma pretreatment of the PET surface, with some improvement in antioxidant efficacy, and the efficacy of the packaging in delaying oxidative deterioration in cooked meats was retained during storage at ambient temperature.

Gegenstand dieser Arbeit ist die retrograde Bewegung des Vakuumbogens, einer Bewegung des Bogenfußes entgegen der Lorentz-Kraft. Die retrograde Bewegung wird auf die Bewegung der Brennflecke des Kathodenansatzes zurückgeführt. Es wurden die Unterstrukturen der Brennflecke und ihre Bewegung im Magnetfeld untersucht. Dabei wurden bekannte makroskopische Erscheinungen (Plasmakante entlang der Magnetfeldlinien) erstmalig beobachteten mikroskopischen Erscheinungen (Jets) zugeordnet. In der vorliegenden Arbeit wurden die Eigenschaften der Jets bestimmt. Desweiteren wurde aus Untersuchungen zur Schrittweite und zeitlichen Abfolge der Brennfleckbewegung unter dem Einfluß des externen Magnetfeldes abgeleitet, daß die zufällige Bewegung des Brennflecks und seiner Bestandteile im magnetfeldfreien Fall auf kleineren Orts- und Zeitskalen als die retrograde Bewegung des Brennflecks (200...300µm) und (1...4µs) erfolgt und damit auch verschiedene Mechanismen ihre Ursache sind. Die beobachteten Jets, die aus dem Brennfleckkern emittiert werden, liefern eine Erklärung für die retrograde Bewegung. In den Jets werden elektrische Felder generiert, welche zur Neuzündung von Brennflecken beitragen. Sie sind der Hauptgrund für die Asymmetrie auf der retrograden Seite (Jets) und der Vorwärtsrichtung (keine Jets). Außerdem konnte gezeigt werden, daß bei heißen Kathoden keine Bewegungsumkehr der retrograden Bewegung erfolgt. Dadurch konnte Klarheit in Bezug auf ältere Veröffentlichungen geschaffen werden, die der retrograden Bewegung eine solche Erscheinung zugeordnet haben. / This thesis treats the phenomenon of retrograde motion of vacuum arcs, the motion of the arc root in the opposite direction of the Lorentz-force. The retrograde motion is attributed to the motion of the cathode spots. The sub-structures of cathodes spots and their motion in a magnetic field were examined. Known macroscopic phenomena (plasma edge along the magnet field lines) were related to observed microscopic phenomena (jets). These jets have been observed for the first time and their properties have been determined. From investigations of typical step widths and time constants of the cathode spots' motion in an external magnetic field it was derived, that random walk and retrograde motion of cathode spots and its fragments in the magnetic field-free case occur on smaller spatial (200...300µm) and temporal (1...4µs) scales than the retrograde motion of the spot. This leads to the conclusion that the mechanisms of both types of motion are different. The observed jets, which are emitted from the spot core, supply an explanation for the retrograde motion. Within the jets electrical fields are generated, which contribute to the ignition of new cathode spots. The jets are the reason for asymmetry on the retrograde side (jets) and the forward direction (no jets). Additionally it could be shown that with hot cathodes no reversal of the retrograde motion occurs. This cleared the assertion of older publications that a reversal of the retrograde motion is linked to the cathode temperature.

Fluidos em uma descarga brilhante à pressão atmosférica usando uma barreira de dielétrico DBD atraiu o interesse das comunidades de termo-dinâmica, fluido-dinâmica, e comunidades de controle. Este trabalho investiga os efeitos de um atuador de plasma operando numa voltagem e frequência de 8 kV e 4.4 kHz sobre a curva do Cp de um cilindro de PVC em baixa velocidade de escoamento. O experimento foi repetido com o atuador em vários ângulos no cilindro. Os resultados mostram uma aceleração do escoamento junto com um atraso da separação. Esses efeitos são maiores quando o atuador é posicionado num ângulo mais próximo da região da separação. / Fluids in a dielectric barrier DBD glow discharge at atmospheric pressure attracted the interest of the communities of thermo and fluid dynamics as well as control. This dissertation investigates the effects of a plasma actuator operating at 8 kV and 4.4 kHz, on the Cp curve of a PVC cylinder in a low velocity airflow. The experiment was repeated with the actuator at various angles. The results show an acceleration of the flow accompanied with a delay of the flow separation. These effects were shown to be larger when the actuator was positioned at an angle closer to the region of separation.

A pulsed-plasma jet (called a "spark-jet" by other researchers), is a high-speed synthetic jet that is generated by striking an electrical discharge in a small cavity. The gas in the cavity pressurizes owing to the heating and is allowed to escape through a small orifice. A series of experiments were conducted to determine the characteristics of the pulsed-plasma jet issuing into stagnant air at a pressure of 45 Torr. These results show that typical jet exit velocities of about 250 m/s can be induced with discharge energies of about 30 mJ per jet. Furthermore, the maximum pulsing frequency was found to be about 5 kHz, because above this frequency the jet begins to misfire. The misfiring appears to be due to the finite time it takes for the cavity to be recharged with ambient air between discharge pulses. The velocity at the exit of the jet is found to be primarily dependent on the discharge current and independent of other discharge parameters such as cavity volume and orifice diameter. Temperature measurements are made using optical emission spectroscopy and reveal the presence of considerable non-equilibrium between rotational and vibrational modes. The gas heating efficiency was found to be 10% and this parameter is shown to have a direct effect on the plasma jet velocity. These results indicate that the pulsed-plasma jet creates a sufficiently strong flow perturbation that is holds great promise as a supersonic flow actuator. An experimental study is conducted to characterize the performance of a pulsed-plasma jet for potential use in supersonic flow control applications. To obtain an estimate of the relative strength of the pulsed-plasma jet, the jet is injected normally into a Mach 3 cross-flow and the penetration distance is measured by using schlieren imaging. These measurements show that the jet penetrates 1.5 [delta], where [delta] is the boundary layer thickness, into the cross-flow and the jet-to-crossflow momentum flux ratio is estimated to be 0.6. An array of pulsed-plasma jets was issued from different locations upstream of a 30-degree compression ramp in a Mach 3 flow. Furthermore, two different jet configurations were used: normal injection and pitched and skewed injection. The pitched and skewed configuration was used to see if the jets could act as high-bandwidth pulsed vortex generators. The interaction between the jets and the separation shock was studied using phase-locked schlieren imaging. Results show that the plasma jets cause a significant disturbance to the separation shock and clearly influence its unsteadiness. While all plasma jet configurations tested caused an upstream motion of the separation shock, pitched and skewed plasma jets caused an initial downstream shock motion before the upstream motion, demonstrating the potential use of these plasma jets as vortex generator jets. The effect of the plasma jet array on the separation shock unsteadiness is studied in a time-resolved manner by using 10 kHz schlieren imaging and fast-response wall pressure measurements. An array of three pulsed-plasma jets, in a pitched and skewed configuration, is used to force the unsteady motion of the interaction formed by a 24° compression ramp in a Mach 3 flow. The Reynolds number of the incoming boundary layer is Re[theta]=3300. Results show that when the pulsed jet array is placed upstream of the interaction, the jets cause the separation shock to move in a quasi-periodic manner, i.e., nearly in sync with the pulsing cycle. As the jet fluid convects across the separation shock, the shock responds by moving upstream, which is primarily due to the presence of hot gas and hence the lower effective Mach number of the incoming flow. Once the hot gases pass through the interaction, the separation shock recovers by moving downstream, and this recovery velocity is approximately 1% to 3% of the free stream velocity. With forcing, the low-frequency energy content of the pressure fluctuations at a given location under the intermittent region decreases significantly. This is believed to be a result of an increase in the mean scale of the interaction under forced conditions. Pulsed-jet injection are also employed within the separation bubble, but negligible changes to the separation shock motion were observed. These results indicate that influencing the dynamics of this compression ramp interaction is much more effective by placing the actuator in the upstream boundary layer. / text

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