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The invention relates to a method ( S ) for generating a plurality of cold - plasma jets at atmospheric pressure in orderto treat a target ( 2 ) , wherein said method includes the following steps : producing ( S1 ) a primary cold - plasma jet( 3 ) at atmospheric pressure using a plasma source ( 10 ) ; placing ( S2 ) a substrate ( 20 , 21 , 30 , 32 , 34 ) near the target( 2 ) to be treated , said substrate ( 20 , 21 , 30 , 32 , 34 ) includingat least two through - holes ; and passing ( S3 ) the plasmathrough the through - holes ( 22 ) of the substrate ( 20 ) such as to generate at least two secondary cold - plasma jets ( 4 ) atatmospheric pressure

International audience; Low temperature plasma treated solutions are under intense study with respect to their key importance for plasma biomedical, plasma environmental and plasma agriculture technologies applications [1,2]. In this work, we report on the use of various plasma jet based delivery protocols likely to generate reactive species enriched solutions for such applications. The baseline setup consists in the use of the Plasma Gun (PG) device [3] delivering a so called plasma plume a few mm away from the liquid to be treated. Such single jet configuration is easily turned into a multi jets setup [4], using a branching capillary assembly, while keeping the same power supply operated with the same voltage amplitude and microsecond pulse repetition rate together with the same range of buffer gas flow rates flushed inside the primary capillary plasma generation reactor. As a second kind of protocol, we report on the liquid solution treatment when plasma reactor capillary is immersed inside liquid solutions, thus resulting in the generation of plasma inside buffer gas bubbles. Reactive species generation in liquid solutions is reported using either plasma plumes or in-bubble plasmas based on the Plasma Gun devices. In-bubble plasma generation with triggering of plasma ignition at different stages of the bubble dynamics, offers opportunities for reactive species balance modulation. Our experiments show that plasma can be delivered in small volume bubbles which then allow for efficient diffusion in the bulk liquid solution, thus opening opportunities for efficient high repetition rate multi bubbles plasma delivery.

International audience; The last decade has seen an impressive increase of the research dedicated to the biological applications of low temperature atmospheric pressure plasmas. Medical applications are tacking an increasing place underlined by many clinical trials. Biological applications extended to agriculture and, more recently, to cosmetic. Despite the huge number of 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.The extremely strong coupling between the plasma characteristics and those of the target (e.g. ref. [1, 2]), plays a very important role in the results observed during 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. In addition, a study recently reported in [3] led to think over 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 of particular importance for the development of efficient systems and protocols for any plasma therapeutic 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.We will discuss the induced changes in gas flow and plasma characteristics, as well as changes induced in microenvironment of living targets. We will emphasize on the fact that plasma diagnostics must be performed in real treatment conditions. We will also tackle the main issues and challenges linked to the control of the multimodal action of non-equilibrium cold plasmas on living organisms.[1] T. Darny, J.M. Pouvesle, J. Fontane et al, PSST, 26 105 001 (2017)[2] T. Darny, J.M. Pouvesle, V. Puech et al, PSST, 26 045 008 (2017)[3] H.R. Metelmann, C. Seebauer, V. Miller et al, Clinical Plasma Medicine 9, 6 (2018)

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

National audience

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; Two methods are described and compared to measure electric fields (EFs) in the plume of an atmospheric pressure plasma jet. The first one uses an electric-optical probe made of a BSO crystal. In this case, the measurement is based on Pockels effect. The second one is Stark spectroscopy of the Helium line at 492nm. From the results obtained, it appears that the presence of a dielectric target triggers an enhancement of the electric field in the plume near the target. Moreover, it will be shown that both techniques have their advantages and are complementary.

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; An organic tissue exposed to plasma experiences a highly reactive environment consisting of ions,electrons, free radicals, UV radiation, neutral molecules and electric field (EF). Of these activeagents, EF is one of the least investigated up to these days [1]. Nevertheless, EF can potentiallyplay a major role transiently increasing cell membrane permeability, a phenomenon commonlyknown as “electroporation” [2] and nowadays effectively used for several applications includinggene transfection and electrochemotherapy [3]. Thus, in the present work, we report the timeresolved measurement of the EF induced in a liquid medium within a typical electroporation setupby a plasma gun (PG) device. The results are compared with the values estimated for aconventional electroporation device (Cliniporator, IGEA SpA) in the perspective of a possibleimpact of plasma induced EF on biological targets. The comparison was done adopting a 4 wellμ-slide (Ibidi®) armed with two plane parallel electrodes used for in-vitro electroporation test andfilled with 500μl of the target liquid, being either SMEM culture medium or high purity water.Three different experimental cases were taken into account (Fig.1, left): 1) the plane electrodespowered by the Cliniporator; 2) the PG plume hitting on one plane electrode; 3) the PG plumehitting on the liquid with (3a) and without (3b) ground electrode. Despite the considerably highervoltage powering the plasma device, preliminary results show an EF on the target lower than theone applied by the electroporation system. This observation goes along with the recorded currentthat results in general one order of magnitude lower for the plasma system. Furthermore, resultsshow a key role played by the grounding of the liquid medium which can hinder the induction ofan EF by the plasma source. While still preliminary, presented results provide new insights on oneof the less investigated aspects of plasma and liquid target interaction, the induced EF.Fig. 1: (left) Photos and schematics of the experimental set up; voltage, current and EF waveformfor case 1 (center) and case 3b (right).This work and A.S. are supported by PLASCANCER project, INCa-PlanCancer-n°17CP087-00References[1] E. Robert, T. Darny, S. Dozias, S. Iseni, J. M. Pouvesle, Physics of Plasma, 22, 122007 (2015).[2] D. Miklavćić; M. Puc, Wiley Encyclopedia of Biomedical Engineering, 1 (2006).[3] L. M. Mir, European J. of Cancer Supplement, 4, 38-44 (2006)

International audience; Atmospheric pressure plasma jets have been extensively studied in the last decade. Thanks tothe production of high transient electric field and reactive nitrogen and oxygen species, manyapplications have been found from material processing to biomedical field. One of the remainingchallenge is the size of the jet. At atmospheric pressure, the plasma plume diameter on a target isof the order of a millimeter leading to difficulties where larger areas must be treated. In order totreat extended wounds, to sterilize wider surfaces or to address large-scale processingapplications, one needs to develop plasma jet arrays.The reactor used in this work is a Plasma Gun made of a high voltage electrode inside a glasscapillary, surrounded by a grounded electrode. A power supply feeds it with 14kV microsecondpulses from single shot to 4 kHz. The pulsed atmospheric pressure plasma stream (PAPS) [1],composed of an ionization wave front followed by a plasma column, originating from thisdielectric barrier discharge, propagates in helium inside the capillary. A linear multijets assemblyis added at the end of the capillary. Plasma multijets production have been studied varyingfollowing parameters: material of the assembly, size of holes, their distance, wall thickness...This work focuses on the differences between a dielectric and a metallic assembly. ICCDcamera recordings show how the ionization wave propagates inside a transparent dielectricassembly, igniting the jets one after another.[2] However, as the PAPS reaches a metallic one, ittransfers its electric potential to the assembly. Then, no plasma propagates into due to theabsence of electric field but new plasma ionization waves are generated at each hole at the sametime. These two different ways of ignition trigger differences in intensity and homogeneitybetween the jets. The presence of species was also investigated via EOS or optical filters. ASchlieren setup has been also used to visualize gas flows with and without plasma with differentgas flow rates, sizes and numbers of holes. With large enough holes the drop of pressure in thedifferent holes becomes visible as jets are shorter and shorter. Additionally to the ionic wind ineach jet, as already studied in [3], interactions between them add a new feature. Repulsive forcesbend the jets, more strongly for the first and last ones and in negative polarity. Electric fieldsmeasurements run with an electro-optic probe, made by Kapteos and based on Pockels effects,with both assemblies will be compared.X.D. acknowledges his grant funding Thermofisher Scientific INEL/Région Centre Val de Loire.References[1] E. Robert, V. Sarron, D. Riès, S. Dozias, M. Vandamme and J M. Pouvesle, Plasma SourcesScience and Technology, 21, 0349017 (2012)[2] AM. Lietz, X. Damany, JM. Pouvesle, E. Robert, MJ. Kushner, Bulletin of the AmericanPhysical Society, 62, Student Excellence Award Finalist: Atmospheric Pressure Plasma Multijets:Fundamental Properties[3] T. Darny, JM. Pouvesle, J. Fontane, L. Joly, S. Dozias, and E. Robert, Plasma SourcesScience and Technology, 26, 105001 (2017).

International audience; Cold atmospheric plasmas (CAPs) have demonstrated to be quite useful tools in biomedicalapplications and their relevance in medicine is getting more and more recognized. Drug deliveryin cancer cells combining low cytotoxicity and high efficiency remains to be optimized withphysical techniques. Several studies have shown that plasma could be used to deliverchemotherapy [1] or nucleic acids [2] via enhancement of cell permeabilization. We investigatedthe parameters needed for helium plasma to induce cell membrane permeabilization on cancercells for drug delivery purposes. 10,000 plasma pulses were used at a frequency of 100 Hz for100 s with an applied voltage of 14 kV. Both plasma electric field and endocytosis involvementin molecular uptake were also studied [3]. Kinetics of plasma-induced permeabilization werestudied. Highest permeabilization efficiency was observed when propidium iodide was addedafter treatment (up to 40% of propidium iodide positive cells in both HeLa and 4T1). Nosignificant toxicity was observed in these conditions as the viability in HeLa cells was measuredto be of 80%. Doxorubicin was used as an anticancer drug. A treatment combining doxorubicinand plasma decreased the concentration of doxorubicin needed to achieve 50% of cytotoxicity byenhancing doxorubicin uptake in cancer cells.References[1] W. Zhu, S.-J. Lee, N. J. Castro, D. Yan, M. Keidar, and L. G. Zhang, Scientific Report, 6,(2016).[2] M. Jinno, Y. Ikeda, H. Motomura, Y. Kido and S. Satoh. Archives BiochemistryBiophysics, 605, 59-66 (2016)[3] V. Vijayarangan, A. Delalande, S. Dozias, J.-M. Pouvesle, C. Pichon, and E.

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)

National audience; Les recherches concernant les applications biomédicales des plasmas froids à la pression atmosphérique ont connu un développement fulgurant au cours des dix dernières années. A côté de la décontamination / stérilisation et du traitement de surface, qui ont déjà une longue histoire grâce à la recherche et aux développements liés aux plasmas à basse pression, les applications médicales connaissent aujourd’hui un essor considérable souligné par de nombreux essais cliniques. Les applications médicales des plasmas à basse température concernent désormais un très large éventail de domaines, notamment l'hémostase primaire et la coagulation sanguine, les soins dentaires, la décontamination et l'hygiène cutanée, le traitement des plaies et des ulcères, la dermatologie, le traitement du cancer. Les applications biologiques sont aussi maintenant étendues à l'agriculture et, plus récemment, à la cosmétique. Malgré le grand nombre d'expériences in vitro et in vivo, il reste encore de nombreuses questions concernant les processus conduisant aux résultats observés et le rôle spécifique des différents « composants » du plasma, eux-mêmes liés à la fois aux dispositifs utilisés et à la présence de la cible vivante (tissus et matériaux biologiques, organes et leur environnement direct). Outre la production de radicaux, nous soulignerons le rôle potentiel du champ électrique généré autour de la plume plasma produite par les jets de plasma atmosphérique et discuterons des changements possibles induits dans le microenvironnement des tissus ou des tumeurs. Nous insisterons également sur le fait que les diagnostics liés aux plasmas doivent être réalisés dans les conditions réelles de traitement.Au cours de cet exposé, après une présentation du contexte, des dispositifs plasma et des principales applications, en considérant le cas spécifique du traitement du cancer, nous aborderons ce qui a déjà été démontré au travers d’expériences in vitro et in vivo, évoquerons les problèmes directement liés aux décharges produites, les défis et les principales perspectives dans le domaine.

National audience

International audience; With the increase of human span life people demand to live and look better. In a world whereappearance is synonymous of health, the demand of new cosmetic has literally exploded. Amongcosmetic treatments, skin care represents a large part of the business of beauty. From 2017 to2023, world-wide non-surgical skin cosmetic treatments business will have a compound annualgrowth rate between 4.7% and 5.3% [1]. The increased demand of non-surgical beautytreatments pushed cosmetic research during the last years. In Europe since 2013 cosmetic testson animal model are definitively banned. This encouraged researchers to develop newapproaches to study skin “in-vitro” using either re-constructed tissue structure or attempting tomimic skin microenvironment parameters. Cell culture has been used since a long time to studyorgan functions in laboratory. In the last decades cell culture has greatly evolved in order tomimic the real tissue structure and microenvironment. Cells are cultivated in three dimensionsand media are adapted to better simulate the extracellular environment. Attempting to get closerto the physiological micro-environment of a cell, scientists underestimated often a keyparameter: the oxygen level [2]. While oxygen represents the 21% of the air gases, in humantissues, its percentage is significantly lower. In skin, it can vary from 7% to 1%. To be as closeas possible to skin microenvironment, in our lab we grow human skin cells either in classicnormoxic condition (18% O2) or in physioxic condition (3% O2). Oxygen has a key role in cellrespiration and in reactive oxygen species (ROS) production. We have already demonstrated thatskin cells raised in physioxia produce lower quantity of reactive oxygen and nitrogen species(RONS) even when exposed to plasma treatment [3]. In this study we evaluated the effect of aCold Atmospheric Plasma (CAP) treatment on human skin cell raised either in normoxia or inphysioxia. In particular, modulating plasma parameters from our helium Plasma Gun, weinvestigated the ability of CAP to improve cell viability and extracellular matrix production suchas collagen, hyaluronic acid and elastin, macromolecules involved in maintaining the health andbeauty of the skin.

International audience; With the current 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 large volumes or even large quantities of liquid or material. If solutions are not found in the short term, this can jeopardize some very promising applications studied on much smaller dimensions. The scale factor then becomes very important and must be treated with the utmost attention. A certain number of systems already make it possible to meet certain constraints, in particular concerning surfaces with very large dimensional surface DBDs that can be used, for example, in the context of decontamination, or for certain applications at the level of the skin (including flexible DBDs). They quickly find their limits when surfaces are more complex or have 3D structures. This problem also arises in the treatment of seeds and plants for applications in agriculture. The conventional single plasma jets allowing only spot type treatments are clearly not well positioned for large scale device developments. In this context, 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 as well as new developments from DBD in specific configurations. Examples of applications will be given in the field of medicine as well as agriculture or liquid treatment.

National audience

International audience; The non-equilibrium low temperature atmospheric pressure plasma (LTAPP) created by electric discharge have characteristics which make them particularly attractive for the development of new applications in the medical field and particularly for new therapeutic applications. This area, now called "Plasma Medicine" has seen dramatic developments in recent years, particularly since 2005-2007. It has been shown, in particular, that many applications can be approached concerning blood coagulation, prevention of the development of bacteria on operated organs, dentistry, dermatology, care on persistent wounds or ulcers, regenerative medicine or treatment of tumors, to name but a few examples. The enthusiasm aroused by research concerning the biomedical applications of cold plasmas is such that now specialized sessions are organized in all major plasma symposia or conferences. If the processes involved are far from being understood, the first clinical applications are emerging. The areas where progress have been most dramatic are certainly the treatment of chronic wounds (wounds or ulcers) for which clinical trials on a large number of patients have already been carried out, and cancer treatment with the first case study recently published. After discussing the sources and dedicated reactors, we will present some important recent developments, notably on the antitumor effect and then present the main issues and challenges.

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.

International audience; A multi-jet plasma source is being developed for large area treatment of surfaces with atmospheric pressure plasma for applications including plasma medicine and surface functionalization. The multi-jet source is a dielectric tube, capped at the end, with a row of holes aligned on one side. Helium flows through the tube and out the holes, where plumes of the He mix with ambient humid air. An ionization wave (IW) begins at a powered electrode upstream of the holes, propagates along the tube and, as passing each hole, launches a separate, secondary ionization wave (SIW) through the hole. The fundamental properties of this system have been investigated using nonPDPSIM, a 2-D plasma hydrodynamics model. The propagation of the SIWs depends on the diameter of the holes, helium flow rate, and voltage polarity. The hole diameter determines the velocity of the SIW as it passes through the holes by controlling the angle of the electric field within the holes. There is an inherent asymmetry in launching the SIW due to charging of one side of the hole by the propagating primary IW. A higher helium flow rate results in a larger region of purer helium outside of the tube, extending the distance the SIW can propagate outside of the hole before encountering air. Positive voltage polarity produces a more uniform plasma within the tube, and increases the intensity of the SIW outside of the tube. Scaling laws will be discussed for and comparisons made to experimental ICCD imaging of the primary IW and SIW, for which there is good agreement.

National audience

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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; In this work, the dynamics of a 1-dimensional plasma jet array at atmospheric pressure have been investigated both experimentally and computationally. The dependence of plasma propagation on parameters such as hole diameter, gas flow and voltage polarity was studied. ICCD imaging, in good agreement with simulations, shows that the hole diameter plays a key role in the ignition of secondary jets. A primary plasma ignited with positive polarity is more likely to produce longer and more intense secondary jets.

International audience; The use of non-thermal atmospheric pressure plasma jet is now widely spread for a large variety of applications in biology, medicine, agriculture, cosmetics, and biomaterials processing. In the use of this type of jet, expanding into the atmosphere, most attention has been paid on the role plaid by the reactive oxygen and nitrogen species, RONS, which are mainly created from the transfers of the energetic species of the used carrier rare gas, mostly helium and argon. The recent results obtained by different teams all around the word, especially in plasma medicine where an action of the treatment has been identify quite deeply in the tissue, tended to show that other plasma components were also playing an important role. Focus has been recently put on the potential action of the electric field generated at the tip of the plasma plume [1] that can reach values of the same order than electric fields commonly used in the medical or industrial applications of Pulsed Electric Field (PEF). That, together with the demonstration of plasma jet induced tissue oxygenation and increase of blood flow [2], shows that the plasma action is much more complex than previously thought. Even, the action of the gas flow must be considered in that it induces local changes in the environment of the treated area in in vivo and in in vitro experiments or biosurface treatment. If we add the fact that potentially the immune system can also be activated, as shown by V. Miller et al [3] or suggested by our group [4] in plasma cancer studies, this evidences that biological applications of plasma jets, and potentially all non-equilibrium cold plasma sources inducing high electric field, must be studied taking into account the changes in the local atmosphere environment (such as effective partial pressure of surrounding gases, especially oxygen and nitrogen, or spot temperature) induced by the plasma source together with the modifications of the microenvironment (local electric field, cell membrane polarization, oxygenation, …, and blood flow in the case of living targets). In this talk, after a general context presentation and a reminder concerning already presented results on tissue oxygenation, increase of blood flow, immune system triggering, we will present results on some of the points raised above (influence of the jet, or multi-jets, on the target atmosphere environment, electric field effect and cell permeabilization in cases of skin cells and cancer cells) and discuss issues, challenges and opportunities linked to this multimodal action of non-equilibrium cold plasmas. [1] E. Robert, T. Darny, S. Dozias et al, PoP, 22 122007 (2015)[2] G. Collet, E. Robert, A. Lenoir et al, PSST, 23 012005 (2014)[3] V. Miller, A. Lin, A, A. Fridman, PCPP, 36 256 (2016)[4] G. Collet, L. Ridou, E. Robert, et al, “NTP Antitumor Soft Treatment: Evidence of a Triggering Effect?” in ICPM5 proceedings, Nara, Japan (2014)Acknowledgments X. Damany, T. Darny, C. Douat, S. Dozias from GREMI, G. Busco, V. Vijayarangan from GREMI and CBM, A. Delalande, C. Grillon, C. Pichon, F. Fasani, S. Morrisset-Lopez, D. Gosset from CBM (Orléans) and A.L. Bulteau, M. Dezet from IPREM (Pau) have participated to part of the presented work. This work is founded by APR PLASMEDNORM, ANR PAMPA, ARD 2020 Cosmetoscience PLASMACOSM project and by the Région Centre-Val de Loire.

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 a large number of remaining questions concerning the processes leading to the observed results, but also the specific role of the different plasma components that are directly linked both to the plasma production devices and the presence of the living target (biological tissues and materials, organs and their direct environment). Taking the example of cancer treatment, beside the radical production, we will emphasize on the potential role of the strong electric field generated around the plasma plume of atmospheric plasma jet systems, and discuss possible changes induced in microenvironment of tissues or tumors. We will also emphasize on the fact that plasma diagnostics must be performed in real treatment conditions.In this talk, after a presentation of the context, the plasma devices, and the main applications, considering the specific case of cancer treatment, we will go through what have been already demonstrated concerning in vitro and in vivo experiments, what problems are directly linked with discharges including recent results on electric field measurements in plasma biological application conditions, what are the challenges in front us, and finishing trying to draw what are the main perspectives in the domain. Acknowledgments X. Damany, T. Darny, C. Douat, S. Dozias from GREMI, G. Busco, V. Vijayarangan from GREMI and CBM, A. Delalande, C. Grillon, C. Pichon, F. Fasani, S. Morrisset-Lopez, D. Gosset from CBM (Orléans), and A.L. Bulteau, M. Dezet from IPREM (Pau) have participated to part of the presented work.This work is founded by APR PLASMEDNORM, ANR PAMPA, ARD 2020 Cosmetoscience PLASMACOSM project and by the Région Centre-Val de Loire.

National audience

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.

National audience

International audience; 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 caries or 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 growth. Also, the longer term effects on plants and potential gene modifications should be considered. Due to seed characteristics, especially designed to survive in aggressive environments during the latency period, this represents a huge challenge not easy to overcome. Low Temperature Non Thermal Plasmas (LTNTP) appear as a very interesting potential treatment in that domain, especially for very high added value seeds, and can open new routes in the seed processing.Due the complex nature of plasmas produced at atmospheric pressure in air, preliminary experiments must be conducted to allow determination of plasma components (at least RONS, UV and Electric field) main action trends. Experiments, dedicated to that, have been conducted on various seeds and discharge systems (including jet, multijets, volumic plasmas, low pressure plasmas) and will be presented with emphasis on growth regulation and potential toxicity. Special emphasis will be put on the appearance of “hormetic” type [1] response (see Fig. 1) that affects the growth of seedling or roots through the antagonist regulation of auxyns and cytokynes versus treatment time. Fig.1 Growth of wheat versus plasma electric field treatment time measured 10, 14 and 18 days after seeding References[1]D. Graves, Clinical Plasma Medicine 2 38 (2014) and Atelier RPF/ABioPlas, Orléans Nov. 16-17, 2015 (from M. Ristow and K. Zarse, Exp. Gerontology, 45, 410 (2010))

International audience

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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)

International audience

L'action des plasmas froids hors équilibre est désormais largement démontrée à la fois in vitro et in vivo (sur des modèles animaux [1,2] et sur l’homme [3,4]) sur de très nombreuses lignées cellulaires, divers types de tumeurs et de maladies. Néanmoins, en raison de la grande variété des composants du plasma capables de jouer un rôle, la compréhension précise de la chaîne de processus conduisant aux effets observés est loin d'être atteinte. Il est difficile d'isoler ou de mesurer l’action individuelle de chaque composante du plasma ou, au contraire, d'évaluer le bénéfice ou la synergie potentielle de leur combinaison. Jusqu'à présent, de nombreuses expériences in vitro ont été réalisées avec cette intention, mais leur transposition in vivo est très compliquée, même, dans de nombreux cas, impossible en raison de l'environnement complexe des cellules in vivo, notamment la vascularisation (impliquant le flux sanguin et l'oxygénation/physioxie) et la réponse du corps (signalisation, recrutement du système immunitaire). En général, la première étape concerne les études consacrées à la viabilité des cellules in vitro ou des études de toxicité dans un milieu de culture avec l'analyse à la fois des changements induits dans les cellules et dans le milieu. Il faut souligner que les conditions expérimentales utilisées, ainsi que le fait de traiter les cellules dans des plaques multipuits en dehors de leur chambre d'incubation peut générer un stress cellulaire qui peut affecter leur comportement et conduire à des résultats biaisés. De plus, même si les jets de plasmas, très largement utilisés dans les applications biomédicales, sont des systèmes relativement simples dans leur conception (principalement à base de réacteur DBD), il n’en reste pas moins que leur étude est complexe, particulièrement dans l’environnement des cibles biologiques. Les interactions entre le plasma lui-même, le débit de gaz et la cible (liquide, tissu, surface inerte) peuvent changer radicalement la production et les interactions des espèces réactives et des espèces chargées pendant les traitements. Enfin, le champ électrique transitoire généré par le jet de plasma peut interagir avec le milieu environnant et, éventuellement, agir en synergie avec les autres composants actifs du plasma délivrés sur la cible.

National audience

International audience; This work reports first on time-resolved measurement of longitudinal and radial electric fields (EF) associated with plasma propagation in dielectric capillaries. Plasma propagation occurs in a region where longitudinal EF exists ahead the ionization front position revealed from plasma emission with ICCD measurement. The ionization front propagation induces the sudden rise of a radial EF component. Both of these EF components have a few kV/cm in amplitude for helium or neon plasmas. Their amplitude is kept almost constant along a few tens of cm long capillary. The key role of the voltage pulse polarity and the drastic impact of the presence of a target in front of the plasma jet are discussed from Schlieren images. All these experimental measurements are in excellent agreement with model calculations which are used to infer EF data on capillary axis. EF diagnostics in the plasma plume in the free jet mode but also in contact with various targets is proposed. The combination of intense transient EF, both of ns and µs duration, together with significant transient reactive species generation during plasma jet treatments may be reconsidered. Typical EF amplitudes likely to induce electrostimulation, electroporation are indeed probably achieved in many in vivo protocols. Stimulation of tissue oxygenation, blood flow rate modulation and more recently immune system triggering may be examples where EF could play a significant role.The second part of this work is dedicated to the development of multi jets, using two different setups, based on a single plasma source. Plasma splitting in dielectric tubes drilled with sub millimetric orifices, but also plasma transfer across metallic tubes equipped with such orifices are analyzed from ICCD imaging and time resolved EF measurements. This allows for the design of plasma jet arrays but also emphasizes the necessity to account for voltage pulse polarity, target potential status, consecutive helium flow modulation and electrostatic influence between the produced secondary jets. The development of plasma arrays based on combination of plasma splitting within dielectric tubes and plasma transfer across metallic tube is reported leading to the generation of tens of secondary jets from a single PG device, i.e a single DBD reactor flushed with 2 l/mn of helium.

International audience

International audience; Atmospheric pressure plasma propagation inside long dielectric tubes is analyzed for the firsttime through nonintrusive and nonperturbative time resolved bi-directional electric field (EF)measurements. This study unveils that plasma propagation occurs in a region where longitudinalEF exists ahead the ionization front position usually revealed from plasma emission with ICCDmeasurement. The ionization front propagation induces the sudden rise of a radial EF component.Both of these EF components have an amplitude of several kV/cm for helium or neon plasmas andare preserved almost constant along a few tens of cm inside a capillary. All these experimentalmeasurements are in excellent agreement with previous model calculations. The key roles of thevoltage pulse polarity and of the target nature on the helium flow patterns when plasma jet isemerging in ambient air are documented from Schlieren visualization. The second part of this workis then dedicated to the development of multi jet systems, using two different setups, based on asingle plasma source. Plasma splitting in dielectric tubes drilled with sub millimetric orifices, butalso plasma transfer across metallic tubes equipped with such orifices are reported and analyzedfrom ICCD imaging and time resolved EF measurements. This allows for the design and thefeasibility validation of plasma jet arrays but also emphasizes the necessity to account for voltagepulse polarity, target potential status, consecutive helium flow modulation, and electrostaticinfluence between the produced secondary jets.