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International audience; Biological applications of Low Temperature Non Thermal Plasmas (LTNTP) have underwent a very rapid development over the recent years and have, even more recently, attracted a lot of attention in the field of agriculture and related domains. Their ability to fight harmful microorganisms and to promote decontamination makes them particularly attractive in that they do not generate chemical residues that must be reprocessed. They are also very attractive to generate interesting reactive species in liquid media that can then be sprayed or used for watering or for soil fertilization. The quality of seeds not only includes their capacity of rapid germination and fruitful growth, but also their protection against, at least, major well know diseases that can threaten their development (for example diseases provoked by Tilletia caries or Ustilago tritici (smut) in the case of wheat). Taking into account the fact that, in the coming years, the new regulations will lead to the impossibility to use the up to now frequently used chemicals, seed producers will have to find new physical treatments if they don’t want to face problems when putting their production on the market. They are then facing another problem: physical treatment must cure seed from pathogens, but, at the same time, they must be totally safe for seed germination and grow. Also, the longer term effects on plants and potential gene modifications should be considered. Due to seed characteristics, especially design to survive in aggressive environments during the latency period, this represents a huge challenge not easy to overcome. LTNTP appear as a very interesting potential treatment in that domain, especially for very high added value seeds and slip, and can open new routes in agriculture processing.On one hand, due the complex nature of plasmas produced at atmospheric pressure in air, experiments must be conducted to allow determination of plasma components (at least RONS and specific species like CO, UV and Electric field) main action trends. On another hand, due to the increasing use of plasma treated water, it is suitable to find new ways of producing different cocktails of usable reactive species of agricultural interest. Experiments, dedicated to that, have been conducted on various seeds and discharge systems (including jet, multijets, volumic plasmas, low pressure plasmas, bubbling plasma treated water) and will be presented.

International audience; The last decade has seen an impressive increase of the research dedicated to the biomedical applications of low temperature plasmas, especially with plasma sources working at atmospheric pressure. In this new trend, beside decontamination/sterilization and surface treatment that have already a quite long story through low-pressure plasma research and developments, medical applications are tacking an increasing place underlined by the actual numerous clinical trials. Medical applications of low temperature plasmas now concern a very wide range of domains, including primary haemostasis and blood coagulation, dental care, skin decontamination and hygiene, wound and ulcer treatment, dermatology, cancer treatment. Biological applications are also now extended to agriculture and, more recently, to cosmetic. Despite the huge number of in vitro and in vivo experiments there are still numerous challenges to overcome linked to the nature of the encountered target (biological tissues and materials, organs and their direct environment, liquids) that have a direct effect on the produced plasma itself and on the generated species. It is clear that the extremely strong coupling between the characteristics of the plasma and those of the target, as already shown, will play a very important role in the results observed during the treatments. A variation in the chemical or physical characteristics of the target will involve significant differences in the gas flow, the local temperature, or the induced electric field, resulting de facto in variations in the production of the reactive species. It also concerns the transposition of the results between the in vitro and the in vivo experiments that are carried out under extremely different conditions, especially concerning the equivalent electric circuit of the reactor / plasma / biological target assembly. These problems directly affect the identification of the processes involved and currently limit the possibility of a definition of a "dose" in plasma treatments. Recently, study reported led to reflections on non-sustainable tumor response. The loss of effectiveness under long-term plasma treatment of cancer tissue opens questions about plasma application and protocol. It must be considered that the treated area is morphologically and chemically changing over the time, from activated surrounding to more normal tissues that are less humid and bacteriologically cleaner. This aspect is particularly important for the development of efficient systems and protocols in plasma cancer treatment but also for any other plasma therapeutically approaches. It induce a in real-time in situ control of plasma production and at longer term a protocol adaptation taking into account the biological target evolution. Some progress are already done in that domain

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International audience; The last decade has seen an impressive increase of the research dedicated to the biomedical applications of low temperature plasmas, especially with plasma sources working at atmospheric pressure. In this new trend, beside decontamination/sterilization and surface treatment which have already a quite long story through low pressure plasma research and developments, medical applications are tacking an increasing place underlined by the actual numerous clinical trials. Medical applications of low temperature plasmas now concern a very wide range of domains, including primary hemostasis and blood coagulation, dental care, skin decontamination and hygiene, wound and ulcer treatment, dermatology, cancer treatment. Biological applications are also now extended to agriculture and, more recently, to cosmetic. Despite the huge number of in vitro and in vivo experiments there are still numerous challenges to overcome linked to the nature of the encountered target (biological tissues and materials, organs and their direct environment, liquids) that have a direct effect on the produced plasma itself and on the generated species. In this talk, after a presentation of the context, the plasma devices, and the main applications, we will focus on the different problems linked to the plasma/target interaction, including treatments of tissues and liquids. Beside the induced changes in gas flow, the radical production and the potential role of the strong electric field generated around the plasma plume of atmospheric plasma jet systems, we will discuss possible changes induced in microenvironment of living targets. Throughout this presentation, we will emphasize on the fact that plasma diagnostics must be performed in real treatment conditions. We will also tackle the main issues, challenges and opportunities linked to the control of these multimodal action of non-equilibrium cold plasmas on living organisms.

International audience; Plasma interactions with liquids has drawn much attention over the past few years considering the interest of water decontamination or treatment of pharmaceutical products. In this context, we studied the potential of low temperature plasmas created inside bubbles using a Plasma Gun (PG) from which the capillary exit is immersed into liquids. Plasma generation inside rare gas bubbles, as well as bubble growth and shape modifications were evidenced through timeresolved ICCD imaging. In this work, we performed experiments in distilled and tap water. For the same used gas, results clearly show that the plasma propagation inside the bubbles and the bubbles behaviour are strongly dependent of the liquid conductivity. These observations, not only, show the importance of the characteristicsof the liquid on the production of the reactive species, but also the importance of the evolution of these characteristics during the treatment time.

International audience; With the nowadays-rapid development of atmospheric plasma applications in the fields of medicine, decontamination, cosmetic and agriculture, researchers are confronted with the development of new sources for treating large surfaces or volumes or great quantities of liquid or material. Single plasma jets have allowed significant advances and the results are particularly promising, but likely to be limited in the future. The treatment times are indeed rather long due to the very small treated surface area or liquid volume resulting from the produced plasma. Surface DBDs, which allow treatment of quite large areas, quickly find their limits when surfaces are more complex or have great 3D structures. There is a real challenge to develop sources that allow treatment over larger areas while remaining practical and at a reasonable cost. The scale factor then becomes very important and must be treated with the outmost attention. In this context, after a rapid review of available systems, some new developments concerning single jets and plasma jets interactions with liquids, we will present results obtained on the development of the sources allowing to treat large surfaces or volumes realized from multijet systems emanating from a single discharge reactor. Examples of applications will be given in the field of medicine or liquid treatment.This work was supported in part by CNRS PEPS project ACUMULTIPLAS, by the ITMO Cancer in the frame of the Plan Cancer, project PLASCANCER N°17CP086-00, and by ARD2020 Cosmetosciences project PLASMACOSM. XD is supported by Thermo Fisher Sci. INEL/Région Centre Val de Loire PhD fellowship. AH is supported by ME NSR PhD fellowship.

International audience; In plasma medicine and agriculture reactive species produced by non-thermal plasmasources must play an important role. Many studies have been devoted on the effects of reactivespecies such as O, O21Δg, OH, N, NO and NO2 species just to name a few. So far, the CO moleculehas been overlooked.Carbon monoxide (CO) is well known for its toxic effects at high doses. The effects of COcan be quantified via the percentage of carboxyhemoglobin (COHb) it forms in the blood. Thepercentage of COHb in blood strongly depends on, not only the percentage of CO in air, but alsoon the exposure time. CO is however also naturally produced at cellular level, mostly via thecatabolism of heme. At low doses, CO has therapeutic properties. Experimental studies foundseveral positive effects of CO such as anti-inflammatory, vasodilatory and anti-apoptotic effects.It has also an influence on plants and promote the seed germination and increases the rootsformation [1].In this contribution, we will shortly review the reactivity of CO at the molecular level andits effects as a signaling molecule. It will be shown that CO triggers and competes with severalcellular receptors which are sensitive to the NO molecule as well.Many studies have demonstrated over the years that plasmas are able to produced CO from thedissociation of CO2 over a wide range of concentrations. Using glow discharges, dielectric barrierdischarges, nanosecond pulsed discharges or microwave plasmas, CO can be produced from ppmrange to several tens %. Plasmas are flexible sources allowing in situ production of CO andalleviate the risks related to its storage. Additionally, plasmas produce other components ofbiological relevance such as electric fields, heat, ultraviolet radiation, O, NO, NO2 and many otherreactive species. Synergic effects may therefore occur for the treatment of certain afflictions. Forinstance, it has been demonstrated that high doses of NO have a pro-inflammatory action [2] whileexogenous CO can down regulates its effects [3]. Plasmas with CO2 admixtures as a source of COseem then promising in applications such as wound healing and seed germination.References[1] E. Carbone and C. Douat, Plasma Medicine, 8(1):93–120 (2018).[2] Guzik TJ, Korbut R, Adamek-Guzik T. Nitric oxide and superoxide in inflammation and immuneregulation. J Physiol Pharmacol. 2003;54(4):469–87.[3] Ingi T, Cheng J, Ronnett G V. Carbon Monoxide: An Endogenous Modulator of the Nitric Oxide–CyclicGMP Signaling System. Neuron. 1996;16(4):835–42.

International audience; Single plasma jets have allowed significant advances in in vivo or directly on human experiments(e.g. [1], [2]). The results are particularly promising, but, ultimately, they couldbe limited in thefuture due to the fact that the treatment times are rather long due to the very small surface areatreated by the produced plasma. There is a real challenge to develop sources that allow treatmentover larger areas while remaining practical and at a reasonable cost. To this end, there arealready flexible or rigid surface DBDs but they require an extremely small distance between thereactor and the treated tissues, which limits their use in many situations (particularly when thetreated surfaces exhibit large variations in the surface morphology leading to points ofattachment of streamers and therefore to a very inhomogeneous treatment). "Ideal" sources aretherefore sources with the flexibility of a jet and treatment surfaces comparable to large DBDs. Itis in this spirit that we have developed a new generation of applicators based on a single PlasmaGun system and able to generate a multitude of jets (from tens up to few hundreds) fromtheprimary plasma jet, as shown in Fig. 1.Fig. 1: Multijet plasma source from single Plasma GunBefore proceeding to in vivo treatments, we qualified the sourcesthrough in vitro experiments ofdecontamination on colonies grown on agar plates in traditional Petri dishes, to check theequivalence of each of the jets generated, as well as on colonies grown onvery large agarsurfacesscanned with our system,to check large surface treatment feasibility. The results are extremelyencouraging and demonstrate the effectiveness of the multijet system, which allows both theprocessing of large-scale targets as well as the reductionof the processing times that otherwisecan be prohibitive with single-jet systems.We will present experimental results obtained on thegeneration of different types of multijets, as well as results obtained with one multijet plasmasource on the decontamination of multi-resistant bacterial colonies grown from hospital inpatientsamples.AcknowledgementsThis work was supported by the CNRS PEPS project ACUMULTIPLAS and the ITMO Cancerin the frame of the Plan Cancer, project N°17CP086-00.References[1] L. Brulé et al, Plos One 7, 0052653 (2012)[2] H R Metelmannet al, CPM, 9, 6(2018)

International audience; Over the past decade, there has been a growing interest in the development of cold atmosphericpressure plasmas for new biomedical applications. This so called Plasma Medicine concernsvarious clinical indications, including infectious diseases and recently, cancer treatment [1].Besides encouraging demonstrations, it has been shown that tolerance and safety issues should beconsidered with great care for any therapeutic application [2]. A new generation of applicators,able to generate multiple jets from a single primary plasma jet, has been developed and qualifiedthrough in vitro experiments. Moreover, they have shown multiple interests (cf. the presentation ofTh. Maho and colleagues in this conference).Using one of these multijet plasma sources, we have proceeded to in vivo treatments on healthymice skin. Various assays have been carried, on nude mice (hairless mice) and CBl57/6 mice (hairymice), which skins have different properties. The distance between the nozzle and the skin surfaceof the treated mouse can be adjusted by applying a spacer (in order to guarantee a constant gapduring treatment - spacer not shown). The presence or absence of skin damages caused by theplasma was assessed as a function of time, distance and delivered power.Fig. 1: Assays of multijet plasma source from single Plasma Gunon Nude mouse (left) and CBl57/6 mouse (right)Between the applicator and the target, plasma jets could appear either clearly separated from eachother or as a more diffuse discharge. Depending on the distance set between the nozzle and thetissue, different thermal effects and skin damages have been observed. The experimental resultsobtained from the characterization of these variables and their effects on the healthy mouse skinsurface will be presented. These promising results will be used as guidance for the application ofmultijet plasma on decontamination procedures (cf. the presentation of Th. Maho et al.).AcknowledgementsThis work was supported by the CNRS PEPS project ACUMULTIPLAS and the ITMO Cancer inthe frame of the Plan Cancer, project N°17CP086-00.References[1] M. Vandamme et al, Plasma Medicine 1(1): 27-43 (2011)[2] S. Kos et al, PLoS ONE 12(4), e0174966 (2017)

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International audience; The study of plasma jets operating in free jet mode and on conductive targets relevant for biomedical applications is discussed. The simultaneous diagnostics of helium metastable through laser absorption, electric field (EF) with an electro-optic probe and current appears as a unique approach to get deep insights on the mechanisms triggered when primary ionization wave (IW), driving the plasma jet propagation, impacts the target. Secondary IWs, back and forth travelling from the plasma jet powered electrode and the grounded target, is measured and may result, depending on the operating parameters of the device, in the transition to a glow like discharge. In such situation, huge enhancement of reactive species production is triggered in connection with significant increase of current flowing through the target. This study allow for a better analysis of the plasma jet delivery on target relevant for biomedical applications and open up opportunities to control reactive species concentration and current amplitude in such experiments. These experimental results are in good agreement with modeling work recently published by group of M.J. Kushner (University of Michigan) on the plasma jet touching or not targets of various natures. The second aspect of the study deals with the characterization of both the amplitude and the topology of the transient EF generated in the vicinity of the plasma jets. Time resolved longitudinal and radial EF, with respect to the jet propagation axis, having amplitudes ranging from a few to a few tens of kV/cm have been measured. There also a good agreement is achieved with modeling data from the group of A. Bourdon (LPP laboratory) which allow extending this diagnostics to region where experimental analysis is hard or disturbing with our probe. It is probably worth considering such intense EF with respect to their potential impact on biological samples.

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International audience; In this work we present Schlieren images of a Plasma Gun discharge fed not only with helium but also for the first time with neon and argon buffers. It is demonstrated that efficient gas flow channelling is observed with operation of the PG with any of the three gases. Such gas flow channelling is also proven to be dependent on voltage polarity and frequency. Analysis of the role of molecular admixtures (N2 or O2) confirms the non-thermal nature of the effect and the potential crucial role of large negative ions.

International audience; Among the many diverse applications of non-thermal atmospheric pressure plasmas (NTAPP), the treatment of liquids has recently drawn a lot of attention, especially for organic pollutant degradation [1]. There are number of possibilities to apply the NTAPP on/in the liquid reported in the literature. In this work, we report on the use of plasma plume produced by a Plasma Gun directed immersed in the solution to be treated. In this case, the plasma is directly produced in the liquid volume without any electrode in contact with the solution.In this work, the plasma is generated with the baseline Plasma Gun [2] setup with a thin diameter (180 μm inner diameter) flexible silicone capillary immersed in a liquid sample and flushed with small rare gas flow rate. A Neon plasma was used with a gas flux of 12,4 sccm, the positive polarity pulse repetition rate was 2 kHz, the silicone capillary of the Plasma Gun is immersed in a quartz tank allowing for absorption spectroscopy measurement during plasma treatment. As a first assessment of plasma in liquid delivery, we investigated the impact of a pulsed atmospheric plasma streams (PAPS) [2] in acetone solutions.Figure 1 represents the spectral absorption of a water solution containing 1000 ppm of acetone, without treatment and for various plasma treatment times. A time dependent evolution of the absorption spectrum over the range from 200 to 400 nm is measured. As we can see, the plasma changes the spectral absorption mainly in the wavelength domain of 280 to 360 nm. Control experiment with only the gas flow applied in the liquid solution verifies that then no change in the absorption spectrum is observed. Most of the changes we observed with plasma where between 280 and 360 even for higher concentration of acetone, but not for pure acetone. This indicates that reactive species generated in the water buffer probably play a critical role in the pollutant chemical degradation. By-products of the liquid solution plasma treatment have not so far been analyzed.[1] E. Marotta et al, Plasma.Proc.Polym 8 867–75.[2] E. Robert et al, Plasma Sources Sci. Technol. 21 (2012) 034017 (12pp)Fig. 1. Absorption profiles for a water/1000 ppm acetone solution treated by Plasma Gun for various treatment times in comparison with not treated solution.

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International audience; In the last decade, plasma jets generated in ambient air at room temperature have found an impressive number of material processing and biomedical applications [1, 2]. While being generated in simple discharge reactors, dielectric barrier discharge or miniaturized plasma torch, it has been rapidly evidenced that their reliable operation and diagnostics was quite challenging and strongly application dependent. In this invited lecture, we will emphasize on the necessity and benefit first to perform plasma diagnostics not only in situation of free jet expansion but more informatively with including target used or mimicking those involved for plasma jet in operation for any dedicated application. It is also crucial to perform combined diagnostics to entangle the number and cross correlated physico chemical phenomena inherent with plasma jet delivery. Recent measurements including gas flow diagnostics with or without plasma operation through Schlieren visualization, species density assessment with IR laser absorption or laser induced fluorescence techniques [3], plasma propagation dynamics and emission diagnostics with fast, eventually wavelength filtered, ICCD imaging, but also electric field measurements [4] will be presented. The necessity to combine various experimental data but also the confrontation with simulation results [5] will be enlighten in the diagnostics of electric fields, radical generation over surface, helium metastable generation and discharge propagation and counter propagation on metallic targets. AcknowledgmentsX.D. is supported through a Région Centre Val de Loire/INEL PhD fellowship.References[1]Penkov O.V. et al, J. Coat. Technol. Res., 12 (2), 225-23 (2015)[2]Laroussi M , IEEE Trans. Plas.Sci., 43 (3), 703-712 (2015)[3]Ries D. et al, J. Phys. D: Appl. Phys. 47 275401 (2014)[4]Robert E. et al, Phys. Plasmas, 22, 122,007 (2015)[5]Bourdon A. et al, accepted PSST (2016)

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