Développement, caractérisation et optimisation d'une source plasma pour la décontamination microbiologique

Abstract : Studies in the plasma-biology field have demonstrated the biocidal effect of atmospheric pressure plasma jets (JPPAs), making these devices an alternative to conventional biological decontamination treatments. The gas (or gas mixture) used and the power injected into the plasma were identified as the parameters influencing the biocidal efficacy of plasma jets. Recently, it has been reported that another factor may influence the biocidal effect of plasma jets: the nature of the target in interaction with the jet. This thesis proposes to study the influence of the nature of a target on the biocidal properties of plasma jets. Initially, the plasma jet was characterized in the absence of a target using electrical (voltage probe, current probe, oscilloscope) and optical (ICCD camera, optical spectrometer) diagnostic tools. The ICCD camera allowed the observation of the propagation of an ionization wave at very high velocities (of the order of km.s-1). Secondly, the characterization focused on the interaction of the plasma jet with a dielectric target (10-10 S.m-1) and a conductive target (6.0 107 S.m-1). The results show that when the ionization wave reaches the dielectric target, it propagates radially on the surface of the target forming a surface ionization wave. For the conductive target, a channel is established between the plasma source and the target surface, possibly followed by propagation of a secondary ionization wave from the target surface towards the plasma source outlet. Finally, the influence of the target nature on the biocidal efficacy of the plasma jet was studied. Endospores suspensions of Bacillus atrophaeus and Escherichia coli bacteria were used as biological indicator. Endospores and bacteria were inoculated on the surface of the dielectric and conductive target and exposed to the plasma jet. The results show different changes on the spores coat's and higher biocidal efficiency for the conductive target compared to the dielectric target. In summary, this thesis shows that the biocide effects of plasma jets should be evaluated under the experimental conditions corresponding to the intended applications.
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Aboubakar Koné. Développement, caractérisation et optimisation d'une source plasma pour la décontamination microbiologique. Plasmas. Université Paul Sabatier - Toulouse III, 2018. Français. ⟨NNT : 2018TOU30142⟩. ⟨tel-02301571⟩

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