A plasma-treated spray (PTS) system is developed to combine gas-phase plasma and plasma-treated droplets for seed treatment. The modular design enables scalable generation of plasma-treated sprays suitable for large-area applications. The effects on germination are evaluated for five crop species: wheat, barley, pea, onion, and beetroot. Plasma treatment improves germination vigor in wheat, barley, and pea. Onion and beetroot show limited or species-specific responses. Electrical characterization demonstrates linear scalability of discharge energy and power consumption over the number of plasma reactor units. The PTS approach achieves competitive energy efficiency and treatment cost, representing a promising step toward sustainable, field-scale plasma applications in agriculture.

This study examined two distinct pulse generators operating with the same reactor, utilizing helium and helium/oxygen mixtures as the working gases. The research focused on the distribution of RONS on the agar surface, their concentration, and the bacterial inhibition halo. The findings demonstrate that modifying the gas mixture influences the concentration of RONS, thereby altering the dominant reactive species and affecting the levels of others during plasma exposure. The incorporation of O 2 into the gas mixture leads to less homogeneous treatment, thereby complicating the eradication of microbes. Nevertheless, it also broadens the spectrum of RONS delivery, which may be beneficial for demanding clinical applications, including tracheal T-tube biofilm control, as preliminary investigated in this work.

The interaction between nanosecond pulsed discharges and acoustically levitated droplets is investigated using time-resolved ICCD imaging, optical emission spectroscopy (OES), electrical diagnostics, and numerical simulations. Experiments are carried out in a pin-to-pin electrode configuration in air at atmospheric pressure with ultra pure water droplets (1 & micro;S.cm-1) and saline droplets (16 mS.cm-1). The results show that the droplet acts as an obstacle contoured by the plasma channel while enhancing the local electric field through polarization, thereby facilitating plasma ignition. For ultra pure water, two streamers develop between the electrodes and the droplet and subsequently merge into a single plasma channel enveloping the droplet surface after approximately 2 ns. In contrast, for saline droplets, electron neutralization at the liquid interface slows streamer propagation along the surface, delaying the merging process. After about 10 ns, however, the discharge evolution becomes similar for both droplet types, regardless of conductivity. The droplet behaves as a capacitor, with its capacitance governing the charging time and influencing early streamer dynamics. Finite element numerical simulations confirm the electric field enhancement near the droplet poles, while evaporation measurements indicate negligible plasma-induced heating, excluding significant Joule effect. Overall, these findings advance the understanding of plasma-droplet interactions and highlight the decisive role of liquid conductivity and dielectric properties in discharge dynamics. The insights gained provide a foundation for optimizing plasma-liquid processes involving droplets in environmental, biomedical, and material science applications.

Experimental research on microfluidic devices requires adequate control over surface parameters like wettability. Plasma has already been proven to be a promising tool for the control and alteration of the wettability of solid surfaces, yet its propagation in microfluidic devices and treatment stability remains challenging. Our idea is to produce and propagate an atmospheric pressure helium plasma directly into closed micrometer-size glass channels for in situ wettability treatment. This approach enables better control over the treatment parameters compared to conventional treatments in low-pressure chamber-type plasma reactors. With a homemade kHz dielectric barrier discharge-like setup, we successfully propagated plasma through a 4 cm long rectangular microchannel of uniform depth ( 100 m ) and variable width (250–500 m ). Results obtained by in situ contact angle measurement on images indicate uniform wettability treatment with increased hydrophilic properties after only 1 min of treatment. The wettability achieved on a glass with our setup offers stability for up to 70 days depending on the plasma treatment and storage parameters. Contact angle results are further supported with X-ray photoelectron spectroscopy (XPS) surface analysis which revealed that the two effective mechanisms for wettability alteration are cleaning and surface functionalization.

As plasma-treated liquids have many applications in plasma medicine, their cutaneous effects for cosmetic purposes are also considered as an alternative way to treat skin without the electric hazards and limitations correlated with the use of a direct plasma. Our previous work on human skin explants showed increased transdermal diffusion of cosmetic ingredients (caffeine, hyaluronic acid) after direct plasma treatment. Despite this proven efficacy, these protocols still face limitations dealing with toxicity, small treatment areas and uneven surface coverage. To overcome these limitations and broaden the scope of non-thermal-plasma-based technology for skin care, this study presents for the first time the development and assessment of a plasma aerosol device to nebulize plasma-treated liquids on skin models. This work demonstrates how plasma jet and plasma treated aerosol can temporarily enhance permeation in reconstructed human epidermis (RHE), using fluorescein as a probe, under safe plasma delivery conditions. Transepithelial electrical resistance measurements confirm the transient nature of the plasma-induced modulation, suggesting the possibility to control the duration of the enhanced permeation. Overall, the achieved results demonstrate the potential of plasma jet and plasma treated aerosol to safely control diffusion through skin for cosmetic and medical purposes.

This paper provides an overview of past and new experimental studies with kHz helium plasma jets and floating-electrode dielectric barrier discharge (DBD) in the context of biomedical applications with the aim to discuss the interaction of plasma jet with skin tissue models. The key motivation is to summarize and address perspectives on the understanding of the mode of action of nonthermal plasma from surface delivery to the biological response of deeper and deeper tissues. First, the significant impact of the target exposed to the plasma jet on the plasma characteristics is documented, highlighting the importance of considering this interaction for in vivo studies. Next, cell permeabilization was first reported and translated to the study of plasma jet permeation of reconstructed epidermis, human explants, and human tissues. Strong analogies are observed in all three substrates, demonstrating a potent but transient modulation of surface features and skin barrier function for a few minutes following a brief plasma exposure time of a few tens of seconds. Interestingly, the modulation of reactive oxygen and nitrogen species generation, so-called RONS, with the variation of the pulse repetition rate of the plasma jet shows no direct correlation with the permeation efficiency. This questions the role of RONS alone in the mode of action of nonthermal plasma for biological response in the few hundreds of microns to the few millimeter tissue layers as was previously also questioned for subcutaneous action of plasma in wound and tumor in vivo treatments. Finally, the combinative role of RONS with electrical factors (charging, current, electric field) is hypothesized and supported with the investigation of deeper living skin tissue oxygenation and vasodilation.

Cold atmospheric pressure plasma (ionized gas) is an innovative medical tool for the treatment of infected wounds thanks to its potential to inactivate drug-resistant microorganisms and promote tissue regeneration and vascularization. The low power consumption, compactness, and versatility of Cold Atmospheric Pressure Plasma (CAPP) devices make them an ideal tool for risk mitigation associated with human spaceflights. This work presents results in microgravity on the operability of CAPP and its antimicrobial effect. The experiments carried out in parabolic flights make it possible to optimize the treatment conditions (i.e., the distance, the gas mixture) and to obtain the rapid inactivation (<15 s) of Escherichia coli samples. Interestingly, the inactivation efficiency of CAPP was higher during parabolic flights than under terrestrial conditions. Overall, these results encourage the further development of CAPP medical devices for its implementation during human spaceflights.

As carbon monoxide has a broad spectrum of biological activities, its production by plasma is a significant advantage in medicine. This paper presents a comparative study of the CO production of two plasma jets: a MHz-jet and a kHz-jet. Both were fed with a helium gas with CO2 admixture (0%-1%). CO was produced by CO2 dissociation and its maximal concentration was hundreds of parts per million, which is safe for clinical applications. For the same specific energy input, the CO production was more efficient for the kHz-jet than the MHz-jet. Both had antibacterial properties on Escherichia coli, and the addition of CO(2 )improved them for the MHz-jet, while it reduced them for the kHz-jet.

Carbon monoxide (CO) has anti-inflammatory properties and its production by plasma could be a significant advantage in the field of plasma medicine. We characterized a pulsed kHz-driven plasma jet to produce CO for biomedical applications. With no target interaction, the CO 2 conversion into CO, the breakdown voltage and energy delivered to the plasma were investigated for two noble carrier gases: helium and argon. The breakdown voltage and the energy delivered to the plasma in argon gas were twice as high as in helium. The breakdown voltage was barely affected by the gas flow rate and the applied voltage, while it decreased slightly with the excitation frequency because the amount of residual charges increases with the frequency. However, the energy delivered to the plasma was not particularly affected by a change in frequency or gas flow rate, while it increased linearly with the applied voltage. CO production rose from a couple of ppm to about 2000 ppm for a specific energy input from 2 to 2000 J/L (5 × 10 −4 to 5200 × 10 −4 eV/(atom or molecule)), making this plasma source safe in terms of CO production for biomedical applications. Unlike literature results, the nature of the noble carrier gas did not have an impact on CO production. The CO concentration produced with 0.3% CO 2 admixture increased linearly with the specific energy input (SEI) until reaching a plateau at about 2100ppm. This implies that loss processes were negligible and that CO 2 dissociation was mainly due to energetic particles such as electrons and excited noble atoms. The conversion decreased with the ratio of CO 2 . Helium and argon as carrier gases are equivalent in terms of CO production and the CO concentration can be controlled by the SEI and the ratio of CO 2 .

This work reports on the demonstration of the penetration of cosmetic active ingredients (caffeine and hyaluronic acid) in human skin explants following safe and controlled plasma jet exposure. First, temperature increase and immunohistochemistry in the stratum corneum and epidermis were characterized to check the safe delivery of plasma jets and to select two operation regimes at 1 and 20 kHz. Plasma exposure for tens of seconds is shown to induce transient modulations of skin pH, transepidermal water loss, and skin wettability, revealing a reversible skin barrier function modulation. Then, it is demonstrated that plasma exposure significantly accelerates the penetration of active ingredients. The tuning of the plasma jet pulse repetition rate allows controlling the penetration kinetics. Such ex vivo results agree with previous in vitro experiments also exhibiting a transient permeabilization time window. A preliminary demonstration of human skin wettability modulation with a low-power, user-friendly dielectric barrier discharge setup is documented, opening perspectives for plasma-based home cosmetic care device development. To the best of our knowledge, this work is one of the first demonstrations of safe and controlled plasma-assisted active ingredients’ skin penetration in the context of cosmetic applications.

Effects of carbon dioxide (CO2) addition and pulsed gliding arc (PGA) plasma on methane (CH4) flame stability and pollutant emissions are investigated in this paper. Two main parts are reported: the effects of CO2 addition to the fuel and the impact of PGA plasma on the characteristics of non-premixed CH4/CO2-air flames in a coaxial swirl burner. The burner consists of 2 concentric tubes, the central tube supplies the CH4 flow and the periphery one supplies the airflow. In the central tube, a metal rod is used as a cathode. To produce the PGA plasma, two other electrodes are symmetrically placed around the central one to obtain two PGA plasma zones in the sta-bilization area of flame. The combustor is a parallelepiped chamber, with a 0.48 m square cross section and 1 m height equipped with six windows on each side. This work primarily focuses on pollutant emissions (NOx and CO), flame structures, and stability. OH* chemiluminescence measurements are used to describe the structure and stability of the flame providing information on the flame lengths and lift-off heights. The lift-off heights and the flame lengths are determined as a function of the CO2 concentrations, ranging from 0% to 50% in the fuel, at a fixed swirl number and equivalence ratio. The results show that CO2 addition to the fuel changes significantly the flame shape and its behavior. The flame becomes more unstable at high CO2 percentages. CO2 addition dilutes reactants, reduces NOx production, and increases CO concentrations in the flue gases. To overcome the instabilities problems due to the addition of CO2, the PGA is used and investigated with different parameters of plasma and flame. PGA plasma is generated by a DC pulsed power generator with HV pulse duration of few microseconds. It is observed that the presence of PGA plasma decreases flame instabilities and reduces CO concentration in the flue gases.

The paper gives the detailed information about a newly developed plasma system applicable for conductive target non-thermal plasma indirect treatment. High voltage microsecond duration pulses delivered in the kHz range are used to ignite a discharge in a glass funnel vessel flushed with argon and equipped with a needle electrode. An air dielectric barrier discharge (DBD) can subsequently be generated if a grounded grid is set a few millimeters apart from the thin glass plate constituting the funnel base, in the funnel-DBD setup. Thus, this air DBD operates with its powered electrode consisting in the transient argon streamer discharge spreading inside the funnel and over the glass plate. This “plasma electrode DBD” is characterized using time-resolved ICCD imaging together with voltage and current probes. This work reports for the first time the funnel-DBD proof of concept operation and its potentialities for large surface decontamination. Argon and air plasma temporal and spatial development is documented and analyzed while electrical characterization using Lissajous plots provide key information on the power and capacitances of the funnel-DBD setup. It is reported that the funnel-DBD operates as a large surface and low power discharge. As with any air-DBD plasma, the modulation of the power density delivered across the air-DBD, processed with changing the pulse repetition rate, results in the control of the ozone concentration. Beyond the plasma electrode-DBD development and characterization, the main motivation of this work is the treatment of conductive samples with the perspective of large surface decontamination. Preliminary demonstrations of the bacterial and yeast inhibition are thus reported for in vitro cultivations through indirect treatment with the funnel-DBD delivering reactive nitrogen and oxygen species.

Recently, Iséni reported measurements and analysis of electric field (EF) strengths adjacent to, and in propagating ionization waves (IWs) for non-thermal atmospheric pressure He plasma jets [1]. This paper [1] is almost the full copy of the 2017 ArXiv :1709.03109v1 [2] for which the authors already published a comment [3]. In this comment, we confirm first that the reported results are wrong due to an improperly aligned electric field probe, and second, that even these wrong measurements are themselves inconsistent.