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Thierry Dufour

Publications and source records attributed to Thierry Dufour.

At least 19 recordsLinked to original sources
arXiv2026

Reactive oxygen species trigger downward vertical migration in diatom microphytobenthic biofilms as a strategy to cope with oxidative stress

Diatom-dominated intertidal microphytobenthic biofilms experience daily fluctuations in irradiance, which can lead to oxidative stress within the photosynthetic apparatus through the production and accumulation of reactive oxygen species. To maintain photosynthetic efficiency, benthic diatoms have developed protective strategies, including mobilization of the antioxidant xanthophyll cycle and the ability to migrate vertically through sediments. However, mechanistic understanding of signaling pathways underlying migration remains poorly characterized. This study investigated the triggering effect of reactive oxygen species on behavioral and photophysiological responses through the analysis of lipophilic pigments and fluorescence parameters. To this end, two microphytobenthic communities, one with sediment allowing vertical migration and another without sediment restricting it, were exposed to irradiance, cold atmospheric plasma, and hydrogen peroxide stresses. Results showed a consistent downward migration response under all oxidative stresses, highlighting the key role of reactive oxygen species, especially hydrogen peroxide, in triggering this microphytobenthic behavior. Moreover, a difference was observed between the pathways involved in vertical migration and those underlying photoprotective responses. Hydrogen peroxide and cold atmospheric plasma stresses highlighted the necessity for substantial microphytobenthic migration, whereas irradiance induced a specific and controlled response involving engagement of the xanthophyll cycle, acting in synergy with the migration strategy by showing stronger activation when migration was impaired.

physics.bio-ph↗
arXiv2026

From Electroculture to Plasma Agriculture: A Three-Century Arc Bridging Bertholon's Legacy with Contemporary Farming Advances

This review traces the historical trajectory of electricity in agriculture, from the earliest observations of electrical phenomena to the emergence of cold plasmas. Looking back to Antiquity and then to the Enlightenment, it underlines Abbé Bertholon's 18th-century efforts to channel atmospheric electricity to stimulate crops, using devices such as the electro-végétomètre. Although these early electroculture experiments relied on neither quantitative dosimetry nor rigorous methodology, they foreshadowed the idea of a controlled transfer of electrical energy to plants. Then the review examines the historical development of galvanism, electrochemistry, and the physics of gaseous discharges throughout the 19th and 20th centuries, which collectively laid the foundations for contemporary cold-plasma technologies. In the 21st century, plasma agriculture has emerged as an interdisciplinary approach integrating electrical, chemical, radiative, thermal, and fluid-mechanical effects. Applications include seed treatment (preconditioning, seed priming), stimulation of plant growth, soil and water treatment, and decontamination of agri-food products. The review thus reassesses Abbé Bertholon's contributions as those of a methodological precursor and shows how his intuition of a "vivifying electricity" resonates with modern cold-plasma science. Finally, it argues that plasma agriculture can transform an Enlightenment intuition into a reproducible experimental framework for sustainable agriculture and food safety.

physics.hist-ph↗
arXiv2026

At the Origins of Electroculture: A Retrodictive Modelling of Bertholon's 18th-Century Electrovegetometer in the Pre-Corona Regime

Pierre-Nicolas Bertholon's 18th-century electrovegetometer was conceived to harness "atmospheric electricity" for plant growth, yet its physical capabilities have never been quantified within the context of today's understanding of the Earth's atmospheric electric system. This study addresses the lack of quantitative assessment of such historical "electroculture" device and its plausible influence on the near-canopy electrical environment. It aims to reinterpret Bertholon's apparatus using contemporary atmospheric electrodynamics, asking under which realistic fair-weather and storm-like conditions a purely passive collector-distributor could generate fields and ion fluxes of physical significance. A two-dimensional, quasi-steady ohmic model has been developed in which the atmosphere is a resistive column carrying the global conduction current, the metal structure is a floating conductor supported by leaky wooden insulators and space-charge and corona are excluded so that all results describe pre-onset upper bounds. The simulations show that in fair weather the single upper point and the lower multi-point crown of the electrovegetometer enhance the background field by two to three orders of magnitude, yet only within millimetric-centimetric regions around the tips and with total currents limited to the pA-nA/m^2 range. Under storm-like forcing, peak fields at the crown reach 100-1000 kV/m, approaching or exceeding empirical corona-onset thresholds, while remaining largely insensitive to uncertainties in apex angle or collector geometry as long as an elevated mast is present. These results make Bertholon's reports of luminous "aigrettes" physically plausible, but suggest that any fair-weather agronomic impact was subtle and highly localized and that modern "electroculture" claims require careful, coupled electrostatic and biological studies beyond the pre-corona regime.

physics.hist-ph↗
arXiv2025

Positive and negative DC glow discharges: a comparative study to characterize self-organized patterns on water surface

Self-organized patterns (SOP) in plasma discharges arise from the complex interplay of electric field, reactive species and charged particles, driven by non-linear plasma dynamics. While studies have explored SOP formation in various configurations, no systematic comparison of positive and negative DC glow discharges has been conducted to explain why SOP form exclusively when polarization is negative. This study aims to analyze SOP formation mechanisms by comparing electrical, optical and spectral properties of positive and negative DC glow discharges interacting with a grounded water surface. Key differences in gas temperature, electric field and reactive species distribution are hence identified. For positive DC glow discharges (PGD), the gas temperature remains in the 350-370 K range, while the reduced electric field remains below 100 Td across the gap. The plasma is dominated by OH and N2* species, whose excitation results from direct electron impact and energy transfer in a low-field environment. The absence of strong ionization and electric field gradients leads to a spatially homogeneous emission layer on the liquid surface, resulting in a circular uniform plasma (CUP) pattern without self-organization. In contrast, SOP emerge exclusively under negative DC glow discharges (NGD) at currents above 15 mA. These discharges present a reduced electric field, peaking at 485 Td at 1mm from the cathode pin, dropping below 100 Td in the central gap and rising to 460 Td near the water surface. There, the plasma layer still contains OH and N2* species but also N2+ ions, the latter being critical for SOP formation. SOP morphology evolves with gap size: at 7 mm, patterns transition from specks to filaments, with pattern diameter and thickness as high as 5.5 mm and 210 μm respectively. Lowering water surface tension with surfactants reduces SOP size and modifies pattern morphology.

physics.plasm-ph↗
arXiv2024

Targeting Cholangiocarcinoma Cells By Cold Piezoelectric Plasmas: In Vitro Efficacy And Cellular Mechanisms

Cold piezoelectric plasma (CPP) is a novel approach in cancer therapy, enabling the development of portable treatment devices capable of triggering cancer cell death. While its effectiveness remains underexplored, this research focuses on its application against cholangiocarcinoma (CCA), an aggressive cancer of the biliary tract. A CPP device is utilized to generate either a corona discharge (Pz-CD) or a dielectric barrier discharge (Pz-DBD) for in vitro experiments. Notably, Pz-CD can deliver more power than Pz-DBD, although both sources produce significant levels of reactive species in plasma and liquid phases. This work shows that CPP causes a gradient increase in medium temperature from the center towards the edges of the culture well, especially for longer treatment times. Although Pz-CD heats more significantly, it cools quickly after plasma extinction. When applied to human CCA cells, CPP shows immediate and long-term effects, more localized for Pz-CD, while more uniform for Pz-DBD. Immediate effects result also in actin cytoskeleton remodeling without alteration of the cell membrane permeability. Long-term effects of CPP, although the antioxidant system is engaged, include activation of the DNA damage response pathway leading to cell death. In conclusion, CPP should be recognized as a promising antitumor therapy.

physics.plasm-ph↗
arXiv2024

Advancements in Maize Cultivation: Synergistic Effects of Dry Atmospheric Plasma Combined with Plasma-Activated Water

In this study, we investigate the effects of pre-germinative and post-germinative plasma treatments, applied separately or in combination, to improve maize germination and early seedling development. Pre-germinative treatment consists of priming the seeds with a dry atmospheric plasma (DAP) generated by a dielectric barrier device (DBD), characterized by minimal radiative emission, low electrical power (4 W) and high emissions of O, OH and NO radicals. Post-germinative treatment, known as plasma-activated water (PAW), uses a single-pin electrode device (SPED) to generate a DC discharge that features a power of 126 W and produces large amounts of OH radicals. The resulting PAW, after 5 minutes of SPED treatment, induces a slight acidification and increased concentrations of nitrate ions (from 24 to 250 mg/L), nitrite ions (from less than 0.1 to 56.1 mg/L) and hydrogen peroxide (from 0.3 to 18.5 mg/L). Results indicate that DAP applied on maize seeds for 20 min boosts their germination rate up to 90% (versus only 65% for untreated seeds) while reducing the median germination time by 37.5%. Then, seedling growth monitoring is achieved on control, DAP, PAW and DAP+PAW groups to assess stem length, hypocotyl length, leaf count, collar diameter and fresh/dry mass. The DAP+PAW group shows the most robust growth, demonstrating a synergistic effect of the combined treatments, particularly with significantly longer stem lengths. Additionally, physiological analyses of seedling leaves indicate a decrease in chlorophyll content despite enhanced growth, while fluorescence microscopy reveals a reduction in stomatal density in leaves treated with DAP and PAW, especially in the combined treatment group, potentially impacting photosynthetic efficiency and water regulation.

physics.plasm-ph↗
arXiv2024

Treatment of seeds by cold ambient air plasma: Combining impedance measurements with water sorption modeling to understand the impact of seed hydration

In this article, we focus on the plasma seed interaction and more specifically-on the feedback exerted by the seeds on the plasma properties. Dormant Arabidopsis seeds with different water contents (WC), namely 3 %DW, 10 %DW and 30%DW were exposed to cold ambient air plasma (C2AP) generated in a dielectric barrier device (DBD). It is found that increasing WC enhances the capacitive current of the DBD, generates a greater number of low energy streamers (characterized by current peaks lower than 10 mA) that preferentially interplay with the seeds. Since the resistive and capacitive components of the seeds modify the C2AP electrical properties, impedance measurements have been carried out to measure their main dielectric parameters before/after plasma exposure (seeds resistance, capacitance, complex relative permittivity, tangent loss and conductivity). WC significantly changes dielectric losses at low frequencies (< 1 kHz) due to polarization relaxation of the polar molecules (i.e. water). LCRmetry further reveals that C2AP does not substantially alter seeds dielectric parameters, i.e. it neither adds or removes significant amounts of new materials, meaning that the relative starch, protein and lipid contents remain essentially unaffected. However, it cannot be discounted that some bulk properties of the Arabidopsis seeds may be modified, especially regarding their porosity. This characteristic could facilitate penetration of plasma-generated reactive oxygen species into the internal seed tissues, leading to the grafting of oxygenated groups. Water sorption isotherms have been achieved on Arabidopsis seeds and fitted with four thermodynamic models, including the Brunauer-Emmett-Teller model and the Generalized D'Arcy and Watt model. It is demonstrated that C2AP primarily strengthens water-seed affinity by modifying molecular interactions rather than changing the seed's moisture layer.

physics.plasm-ph↗
arXiv2023

Release of Arabidopsis seed dormancy by cold atmospheric plasma relies on cytoplasmic glass transition

When mature Arabidopsis thaliana seeds are dormant, their germination is prevented in apparently favourable conditions. This primary dormancy can be released during seed dry storage through a process called after-ripening whose duration can last several months. To reduce this delay, cold atmospheric plasmas (CAP) can be used as sources of reactive oxygen species capable of inducing heterogeneous chemical reactions. While CAP are known to stimulate the germination of various seed species, the relationship between CAP treatments and the amorphous solid state of dry seeds remains unexplored. Here, we demonstrate that seed dormancy can be alleviated using a cold plasma of ambient air and that this alleviation can be amplified for seeds with high water-content (typically 30 %DW) or seeds heated at 60 °C during plasma treatment. Differential scanning micro-calorimetry shows that these characteristics control the glassy/rubbery state of the seed cytoplasm. This technique indicates also that a glass transition to the rubbery state strengthens the CAP effects to alleviate seed dormancy. We propose that lower cytoplasmic viscosity can promote the oxidative signaling induced by CAP which, in turn, improves the germination process.

physics.plasm-ph↗
arXiv2023

From Basics to Frontiers: A Comprehensive Review of Plasma-Modified and Plasma-Synthesized Polymer Films

This comprehensive review begins by tracing the historical development and progress of cold plasma technology as an innovative approach to polymer engineering. The study emphasizes the versatility of cold plasma derived from a variety of sources including low-pressure glow discharges (e.g., radiofrequency capacitively coupled plasmas) and atmospheric pressure plasmas (e.g., dielectric barrier devices, piezoelectric plasmas). It critically examines key operational parameters such as reduced electric field, pressure, discharge type, gas type and flow rate, substrate temperature, gap, and how these variables affect the properties of the synthesized or modified polymers. This review also discusses the application of cold plasma in polymer surface modification, underscoring how changes in surface properties (e.g., wettability, adhesion, biocompatibility) can be achieved by controlling various surface processes (etching, roughening, crosslinking, functionalization, crystallinity). A detailed examination of Plasma-Enhanced Chemical Vapor Deposition (PECVD) reveals its efficacy in producing thin polymeric films from an array of precursors. Yasuda's models, Rapid Step-Growth Polymerization (RSGP) and Competitive Ablation Polymerization (CAP), are explained as fundamental mechanisms underpinning plasma-assisted deposition and polymerization processes. Then, the wide array of applications of cold plasma technology is explored, from the biomedical field, where it is used in creating smart drug delivery systems and biodegradable polymer implants, to its role in enhancing the performance of membrane-based filtration systems crucial for water purification, gas separation, and energy production. It investigates the potential for improving the properties of bioplastics and the exciting prospects for developing self-healing materials using this technology.

physics.plasm-ph↗
arXiv2023

Cold plasma endoscopy applied to biliary ducts: feasibility risk assessment on human-like and porcine models for the treatment of cholangiocarcinoma

For the past twelve years, cold plasmas have been positioned as a breakthrough technology for treating cancer thanks to their antitumor properties. The innovation of ad hoc plasma sources and personalized protocols appears crucial to treat cancers with a very poor prognosis. This is the case for cholangiocarcinoma (CCA) , whose treatment with cold plasma requires the innovation of catheters and endoscopic devices for local therapies. Before conducting clinical trials, the performances and limitations of cold plasma endoscopy must be evaluated in terms of safety for both the patient and clinician as well as in terms of therapeutic efficacy. These objectives are pursued in the present work, in which a transferred plasma catheter is used, powered by 8-10 kV, 5-10 kHz repeated pulses, allowing guided streamers to be transferred over lengths of at least 2 m. In a first step, the catheter is directly inserted into an artificial model reproducing the topography and the electrical response of the biliary tree. This model allows to validate the technical feasibility of the technology and to demonstrate the absence of electrical and thermal risks. In a second step, the catheter is inserted into the duodenoscope, the whole being applied to a porcine anatomical model. After passing through the esophagus, stomach and duodenum, the distal part of the duodenoscope is placed at the entrance to the papilla so that the catheter can easily enter the choledoc and then the common bile duct. Interestingly, the electrical power values deposited are of the order of 100 mW especially because the current values are at least 10 times higher. The absence of electrical and thermal risks is demonstrated and consolidated by the IEC standards for medical devices. In a third time, we demonstrate that the cold plasma catheter can induce antitumor effects on in vitro experimental models of human CCA.

physics.med-ph↗
arXiv2023

Cyto- and bio-compatibility assessment of plasma-treated polyvinylidene fluoride scaffolds for cardiac tissue engineering

As part of applications dealing with cardiovascular tissue engineering, drop-cast polyvinylidene fluoride (PVDF) scaffolds have been treated by cold plasma to enhance their adherence to cardiac cells. The scaffolds were treated in a dielectric barrier device where cold plasma was generated in a gaseous environment combining a carrier gas (helium or argon) with/without a reactive gas (molecular nitrogen). We show that an Ar-N2 plasma treatment of 10 min results in significant hydrophilization of the scaffolds, with contact angles as low as 52.4° instead of 132.2° for native PVDF scaffolds. Correlation between optical emission spectroscopy and X-ray photoelectron spectroscopy shows that OH radicals from the plasma phase can functionalize the surface scaffolds, resulting in improved wettability. For all plasma-treated PVDF scaffolds, the adhesion and maturation of primary cardiomyocytes is increased, showing a well-organized sarcomeric structure (α-actinin immunostaining). The efficacy of plasma treatment was also supported by real-time PCR analysis to demonstrate an increased expression of the genes related to adhesion and cardiomyocyte function. Finally, the biocompatibility of the PVDF scaffolds was studied in a cardiac environment, after implantation of acellular scaffolds on the surface of the heart of healthy mice. Seven and 28 days after implantation, no exuberant fibrosis and no multinucleated giant cells were visible in the grafted area, hence demonstrating the absence of foreign body reaction and the biocompatibility of these scaffolds.

q-bio.TO↗
arXiv2021

Direct current parallel microdischarges in helium

Parallel Micro Hollow Cathodes Discharges are characterised by electrical and spectroscopic studies and by using an ICCD camera. V-I curves present a hysteresis cycle between Townsend and normal glow regimes. For I d =4-10mA, gas temperature ranges between 300-500{\textdegree}C. When the diameter of a hole decreases, a more significant discharge voltage is needed.

physics.plasm-ph↗
arXiv2020

Seed-packed dielectric barrier device for plasma agriculture: understanding its electrical properties through an equivalent electrical model

Seeds have been packed in a dielectric barrier device where cold atmospheric plasma has been generated to improve their germinative properties. A special attention has been paid on understanding the resulting plasma electrical properties through an equivalent electrical model whose experimental validity has been demonstrated here. In this model, the interelectrode gap is subdivided into 4 types of elementary domains, according to whether they contain electric charges (or not) and according to their type of medium (gas, seed or insulator). The model enables to study the influence of seeds on the plasma electrical properties by measuring and deducing several parameters (charge per filament, gas capacitance, plasma power, ...) either in no-bed configuration (i.e. no seed in the reactor) or in packed-bed configuration (seeds in the reactor). In that second case, we have investigated how seeds can influence the plasma electrical parameters considering six specimens of seeds (beans, radishes, corianders, lentils, sunflowers and corns). The influence of molecular oxygen (0-100 sccm) mixed with a continuous flow rate of helium (2 slm) is also investigated, especially through filaments breakdown voltages, charge per filament and plasma power. It is demonstrated that such bed-packing drives to an increase in the gas capacitance, to a decrease in the beta-parameter and to variations of the filaments' breakdown voltages in a seed-dependent manner. Finally, we show how the equivalent electrical model can be used to assess the total volume of the contact points, the capacitance of the seeds in the packed-bed configuration and we demonstrate that germinative effects can be induced by plasma on four of the six agronomical specimens.

physics.app-ph↗
arXiv2020

Cold-atmospheric plasma induces tumor cell death in preclinical in vivo and in vitro models of human cholangiocarcinoma

Through the last decade, cold atmospheric plasma (CAP) has emerged as an innovative therapeutic option for cancer treatment. Recently, we have set up a potentially safe atmospheric pressure plasma jet device that displays antitumoral properties in a preclinical model of cholangiocarcinoma (CCA), a rare and very aggressive cancer emerging from the biliary tree with few efficient treatments. In the present study, we aimed at deciphering the molecular mechanisms underlying the antitumor effects of CAP towards CCA both in an in vivo and in vitro context. In vivo, using subcutaneous xenografts into immunocompromised mice, CAP treatment of CCA induced DNA lesions and tumor cell apoptosis, as evaluated by 8-oxoguanine and cleaved caspase-3 immunohistochemistry, respectively. Analysis of the tumor microenvironment showed changes in markers related to macrophage polarization. In vitro, incubation of CCA cells with CAP-treated culture media (i.e. plasma-activated media, PAM) led to a dose response decrease in cell survival. At molecular level, CAP treatment induced double-strand DNA breaks, followed by an increased phosphorylation and activation of the cell cycle master regulators CHK1 and p53, leading to cell cycle arrest and cell death by apoptosis. In conclusion, CAP is a novel therapeutic option to consider for CCA in the future.

q-bio.TO↗
arXiv2019

Self-organized patterns by a DC pin liquid anode discharge in ambient air: Effect of liquid types on formation

A pin liquid anode DC discharge is generated in open air without any additional gas feeding to form self-organized patterns (SOPs) on various liquid interfaces. Axially resolved emission spectra of the whole discharge reveal that the self-organized patterns are formed below a dark region and are visible mainly due to the N2 transitions. The high energy N2 (C) level is mainly excited by the impact of electrons heated by the local increased electric field at the interface. For the first time, the effect of the liquid type on the SOP formation is presented. With almost the same other discharge conditions, the formed SOPs are significantly different from HCl and H2SO4 liquid anodes. The SOP difference is repeated when the discharge current and gap distance change for both liquid anodes. The variations of SOP size and discretization as a function of discharge current and gap distance are discussed and confirm that different SOPs are formed by the HCl liquid anode from tap water or the H2SO4 liquid anode. A possible explanation is brought up to explain the dependence of SOPs on the liquid type.

physics.plasm-ph↗
arXiv2019

Plasma gun for medical applications: engineering an equivalent electrical target of human body and deciphering relevant electrical parameters

Simulations and experimental works have been carried out in a complementary way to engineer a basic material target mimicking the same dielectric properties of the human body. It includes a resistor in parallel with a capacitor, whose values (Rh=1500 Ω and Ch=100 pF) are estimated in regard of parameters commonly utilized upon in vivo campaigns (frequency=30 kHz, gap=10 mm, high voltage electrode surface=12.6 mm2). This equivalent electrical human body (EEHB) circuit can be used as a reference and realistic target to calibrate electrical properties of therapeutic plasma sources before their utilization on patients. In this letter, we consider a configuration where this EEHB target interacts with a plasma gun (PG). Plasma power measurements performed in such configuration clearly indicate two operating modes depending on the value of the supplied voltage. Hence, the plasma gun generates pulsed atmospheric plasma streams likely to present therapeutic interest for voltages comprised between 3.0 and 8.5 kV while for higher values, transient arcs of thermal plasma are generated and represent substantial risks for the patient.

physics.app-ph↗
arXiv2018

Synthesis of Membrane-Electrode Assembly for Fuel Cells by Means of (Sub)-Atmospheric Plasma Processes

An easy procedure to build up membrane-electrode assemblies for applications dedicated to miniaturized PEMFC using H2 or CH3OH by a two-steps atmospheric plasma process is reported. Firstly, catalyst nanoparticles are grafted on carbon substrates by spraying a Pt colloidal solution in the post-discharge of an RF atmospheric plasma torch. In the second step, the resulting decorated electrodes are covered by plasma synthesized polymeric membranes in the discharge of a DBD. The sulfonated polystyrene membranes are synthesized by injecting simultaneously styrene and trifluoromethanesulfonic acid monomers, in the presence of a carrier gas (Ar or He). The membranes are chemically characterized by XPS, ToF-SIMS, and FTIR (IRRAS) and their deposition rate is investigated by SEM.

physics.app-ph↗