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“Atomic scale understanding of the permeation of plasma species across native and oxidized membranes”. Razzokov J, Yusupov M, Cordeiro RM, Bogaerts A, Journal of physics: D: applied physics 51, 365203 (2018). http://doi.org/10.1088/1361-6463/aad524
Abstract: Cold atmospheric plasmas (CAPs) have attracted significant interest for their potential benefits in medical applications, including cancer therapy. The therapeutic effects of CAPs are related to reactive oxygen and nitrogen species (ROS and RNS) present in the plasma. The impact of ROS has been extensively studied, but the role of RNS in CAP-treatment remains poorly understood at the molecular level. Here, we investigate the permeation of RNS and ROS across native and oxidized phospholipid bilayers (PLBs) by means of computer simulations. The results reveal significantly lower free energy barriers for RNS (i.e. NO, NO2, N2O4) and O3 compared to hydrophilic ROS, such as OH, HO2 and H2O2. This suggests that the investigated RNS and O3 can permeate more easily through both native and oxidized PLBs in comparison to hydrophilic ROS, indicating their potentially important role in plasma medicine.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 10
DOI: 10.1088/1361-6463/aad524
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“CF4 decomposition in a low-pressure ICP : influence of applied power and O2 content”. Setareh M, Farnia M, Maghari A, Bogaerts A, Journal of physics: D: applied physics 47, 355205 (2014). http://doi.org/10.1088/0022-3727/47/35/355205
Abstract: This paper focuses on the investigation of CF4 decomposition in a low-pressure inductively coupled plasma by means of a global model. The influence of O2 on the CF4 decomposition process is studied for conditions used in semiconductor manufacturing processes. The model is applied for different powers and O2 contents ranging between 2% and 98% in the CF4/O2 gas mixture. The model includes the reaction mechanisms in the gas phase coupled with the surface reactions and sticking probabilities of the species at the walls. The calculation results are first compared with experimental results from the literature (for the electron density, temperature and F atom density) at a specific power, in the entire range of CF4/O2 gas mixture ratios, and the obtained agreements indicate the validity of the model. The main products of the gas mixture, obtained from this model, include CO, CO2 and COF2 together with a low fraction of F2. The most effective reactions for the formation and loss of the various species in this process are also determined in detail. Decomposition of CF4 produces mostly CF3 and F radicals. These radicals also contribute to the backward reactions, forming again CF4. This study reveals that the maximum decomposition efficiency of CF4 is achieved at a CF4/O2 ratio equal to 1, at the applied power of 300 W.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 8
DOI: 10.1088/0022-3727/47/35/355205
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“The 2017 Plasma Roadmap: Low temperature plasma science and technology”. Adamovich I, Baalrud SD, Bogaerts A, Bruggeman PJ, Cappelli M, Colombo V, Czarnetzki U, Ebert U, Eden JG, Favia P, Graves DB, Hamaguchi S, Hieftje G, Hori M, Kaganovich ID, Kortshagen U, Kushner MJ, Mason NJ, Mazouffre S, Thagard SM, Metelmann H-R, Mizuno A, Moreau E, Murphy AB, Niemira BA, Oehrlein GS, Petrovic ZL, Pitchford LC, Pu Y-K, Rauf S, Sakai O, Samukawa S, Starikovskaia S, Tennyson J, Terashima K, Turner MM, van de Sanden MCM, Vardelle A, Journal of physics: D: applied physics 50, 323001 (2017). http://doi.org/10.1088/1361-6463/aa76f5
Abstract: Journal of Physics D: Applied Physics published the first Plasma Roadmap in 2012
consisting of the individual perspectives of 16 leading experts in the various sub-fields of low temperature plasma science and technology. The 2017 Plasma Roadmap is the first update of a planned series of periodic updates of the Plasma Roadmap. The continuously growing interdisciplinary nature of the low temperature plasma field and its equally broad range of applications are making it increasingly difficult to identify major challenges that encompass all of the many sub-fields and applications. This intellectual diversity is ultimately a strength of the field. The current state of the art for the 19 sub-fields addressed in this roadmap demonstrates the enviable track record of the low temperature plasma field in the development of plasmas as an enabling technology for a vast range of technologies that underpin our modern society. At the same time, the many important scientific and technological challenges shared in this roadmap show that the path forward is not only scientifically rich but has the potential to make wide and far reaching contributions to many societal challenges.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 246
DOI: 10.1088/1361-6463/aa76f5
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“Investigating the plasma chemistry for the synthesis of carbon nanotubes/nanofibres in an inductively coupled plasma-enhanced CVD system : the effect of processing parameters”. Mao M, Bogaerts A, Journal of physics: D: applied physics 43, 315203 (2010). http://doi.org/10.1088/0022-3727/43/31/315203
Abstract: A parameter study is carried out for an inductively coupled plasma used for the synthesis of carbon nanotubes or carbon nanofibres (CNTs/CNFs), by means of the Hybrid Plasma Equipment Model. The influence of processing parameters including gas ratio for four different gas mixtures typically used for CNT/CNF growth (i.e. CH4/H2, CH4/NH3, C2H2/H2 and C2H2/NH3), inductively coupled plasma (ICP) power (501000 W), operating pressure (10 mTorr1 Torr), bias power (01000 W) and temperature of the substrate (01000 °C) on the plasma chemistry is investigated and the optimized conditions for CNT/CNF growth are analysed. Summarized, our calculations suggest that a lower fraction of hydrocarbon gases (CH4 or C2H2, i.e. below 20%) and hence a higher fraction of etchant gases (H2 or NH3) in the gas mixture result in more 'clean' conditions for controlled CNT/CNF growth. The same applies to a higher ICP power, a moderate ICP gas pressure above 100 mTorr (at least for single-walled carbon nanotubes), a high bias power (for aligned CNTs) and an intermediate substrate temperature.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 17
DOI: 10.1088/0022-3727/43/31/315203
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“Phototoxicity and cell passage affect intracellular reactive oxygen species levels and sensitivity towards non-thermal plasma treatment in fluorescently-labeled cancer cells”. Verswyvel H, Deben C, Wouters A, Lardon F, Bogaerts A, Smits E, Lin A, Journal of physics: D: applied physics 56, 294001 (2023). http://doi.org/10.1088/1361-6463/accc3d
Abstract: Live-cell imaging with fluorescence microscopy is a powerful tool, especially in cancer research, widely-used for capturing dynamic cellular processes over time. However, light-induced toxicity (phototoxicity) can be incurred from this method, via disruption of intracellular redox balance and an overload of reactive oxygen species (ROS). This can introduce confounding effects in an experiment, especially in the context of evaluating and screening novel therapies. Here, we aimed to unravel whether phototoxicity can impact cellular homeostasis and response to non-thermal plasma (NTP), a therapeutic strategy which specifically targets the intracellular redox balance. We demonstrate that cells incorporated with a fluorescent reporter for live-cell imaging have increased sensitivity to NTP, when exposed to ambient light or fluorescence excitation, likely through altered proliferation rates and baseline intracellular ROS levels. These changes became even more pronounced the longer the cells stayed in culture. Therefore, our results have important implications for research implementing this analysis technique and are particularly important for designing experiments and evaluating redox-based therapies like NTP.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Center for Oncological Research (CORE)
Impact Factor: 3.4
DOI: 10.1088/1361-6463/accc3d
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“Computer simulations of plasmabiomolecule and plasmatissue interactions for a better insight in plasma medicine”. Neyts EC, Yusupov M, Verlackt CC, Bogaerts A, Journal of physics: D: applied physics 47, 293001 (2014). http://doi.org/10.1088/0022-3727/47/29/293001
Abstract: Plasma medicine is a rapidly evolving multidisciplinary field at the intersection of chemistry, biochemistry, physics, biology, medicine and bioengineering. It holds great potential in medical, health care, dentistry, surgical, food treatment and other applications. This multidisciplinary nature and variety of possible applications come along with an inherent and intrinsic complexity. Advancing plasma medicine to the stage that it becomes an everyday tool in its respective fields requires a fundamental understanding of the basic processes, which is lacking so far. However, some major advances have already been made through detailed experiments over the last 15 years. Complementary, computer simulations may provide insight that is difficultif not impossibleto obtain through experiments. In this review, we aim to provide an overview of the various simulations that have been carried out in the context of plasma medicine so far, or that are relevant for plasma medicine. We focus our attention mostly on atomistic simulations dealing with plasmabiomolecule interactions. We also provide a perspective and tentative list of opportunities for future modelling studies that are likely to further advance the field.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 28
DOI: 10.1088/0022-3727/47/29/293001
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“The origin of Bohm diffusion, investigated by a comparison of different modelling methods”. Bultinck E, Mahieu S, Depla D, Bogaerts A, Journal of physics: D: applied physics 43, 292001 (2010). http://doi.org/10.1088/0022-3727/43/29/292001
Abstract: 'Bohm diffusion' causes the electrons to diffuse perpendicularly to the magnetic field lines. However, its origin is not yet completely understood: low and high frequency electric field fluctuations are both named to cause Bohm diffusion. The importance of including this process in a Monte Carlo (MC) model is demonstrated by comparing calculated ionization rates with particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations. A good agreement is found with a Bohm diffusion parameter of 0.05, which corresponds well to experiments. Since the PIC/MCC method accounts for fast electric field fluctuations, we conclude that Bohm diffusion is caused by fast electric field phenomena.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 16
DOI: 10.1088/0022-3727/43/29/292001
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“Kinetic modelling for an atmospheric pressure argon plasma jet in humid air”. Van Gaens W, Bogaerts A, Journal of physics: D: applied physics 46, 275201 (2013). http://doi.org/10.1088/0022-3727/46/27/275201
Abstract: A zero-dimensional, semi-empirical model is used to describe the plasma chemistry in an argon plasma jet flowing into humid air, mimicking the experimental conditions of a setup from the Eindhoven University of Technology. The model provides species density profiles as a function of the position in the plasma jet device and effluent. A reaction chemistry set for an argon/humid air mixture is developed, which considers 84 different species and 1880 reactions. Additionally, we present a reduced chemistry set, useful for higher level computational models. Calculated species density profiles along the plasma jet are shown and the chemical pathways are explained in detail. It is demonstrated that chemically reactive H, N, O and OH radicals are formed in large quantities after the nozzle exit and H2, O2(1Δg), O3, H2O2, NO2, N2O, HNO2 and HNO3 are predominantly formed as 'long living' species. The simulations show that water clustering of positive ions is very important under these conditions. The influence of vibrational excitation on the calculated electron temperature is studied. Finally, the effect of varying gas temperature, flow speed, power density and air humidity on the chemistry is investigated.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 115
DOI: 10.1088/0022-3727/46/27/275201
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“Inactivation of human pancreatic ductal adenocarcinoma with atmospheric plasma treated media and water: a comparative study”. Kumar N, Attri P, Dewilde S, Bogaerts A, Journal of physics: D: applied physics 51, 255401 (2018). http://doi.org/10.1088/1361-6463/aac571
Abstract: In recent years, the interest in treating cancer cells with plasma treated media (PTM) and plasma treated water (PTW) has increased tremendously. However, the actions of PTM and PTW are still not entirely understood. For instance, it is not clear whether the action of PTM is due to a modification in proteins/amino acids after plasma treatment of the media, or due to reactive oxygen and nitrogen species (RONS) generated from the plasma, or a combination of both effects. To differentiate between the actions of RONS and modified proteins/amino acids on the treatment of cancer cells, we compared the effects of PTM and PTW on two different pancreatic ductal adenocarcinomas (MiaPaca-2, BxPc3) and pancreatic stellate cells
(PSCs) (hPSC128-SV). PSCs closely interact with cancer cells to create a tumor-promoting environment that stimulates local tumor progression and metastasis. We treated culture media and deionized water with a cold atmospheric plasma (CAP) jet, and subsequently applied this PTM/PTW at various ratios to the pancreatic cancer and PSC cell lines. We evaluated cell death, intracellular ROS concentrations and the mRNA expression profiles of four oxidative stress-related genes, i.e. Mitogen-activated protein kinase 7 (MAPK7), B-cell lymphoma 2 (BCL2), Checkpoint kinase 1 (CHEK1) and DNA damage-inducible transcript 3, also known as C/EBP homologous protein (CHOP). Our findings demonstrate that PTM and PTW have a similar efficacy to kill pancreatic cancer cells, while PTW is slightly more effective in killing PSCs, as compared to PTM. Furthermore, we observed an enhancement of the intracellular ROS concentrations in both pancreatic cancer cells and PSCs. Thus, it is likely that under our experimental conditions, the anti-cancer activity of PTM can be attributed more to the RONS present in the treated liquid, than to the modification of proteins/amino acids in the media. Furthermore, the fact that the chemo-resistant PSCs were killed by PTM/PTW may offer possibilities for new anti-cancer therapies for pancreatic cancer cells, including PSCs.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 6
DOI: 10.1088/1361-6463/aac571
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“Role of vibrationally excited HBr in a HBr/He inductively coupled plasma used for etching of silicon”. Tinck S, Bogaerts A, Journal of physics: D: applied physics 49, 245204 (2016). http://doi.org/10.1088/0022-3727/49/24/245204
Abstract: In this work, the role of vibrationally excited HBr (HBr(vib)) is computationally investigated for a HBr/He inductively coupled plasma applied for Si etching. It is found that at least 50% of all dissociations of HBr occur through HBr(vib). This additional dissociation pathway through HBr(vib) makes the plasma significantly more atomic. It also results in a slightly higher electron temperature (i.e. about 0.2 eV higher compared to simulation results where HBr(vib) is not included), as well as a higher gas temperature (i.e. about 50 K higher than without including HBr(vib)), due to the enhanced Franck–Condon heating through HBr(vib) dissociation,
at the conditions investigated. Most importantly, the calculated etch rate with HBr(vib) included in the model is a factor 3 higher than in the case without HBr(vib), due to the higher fluxes of etching species (i.e. H and Br), while the chemical composition of the wafer surface shows no significant difference. Our calculations clearly show the importance of including HBr(vib) for accurate modeling of HBr-containing plasmas.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
DOI: 10.1088/0022-3727/49/24/245204
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“Bulk plasma fragmentation in a C4F8 inductively coupled plasma : a hybrid modelling study”. Zhao S-X, Zhang Y-R, Gao F, Wang Y-N, Bogaerts A, Journal of applied physics 117, 243303 (2015). http://doi.org/10.1063/1.4923230
Abstract: A hybrid model is used to investigate the fragmentation of C4F8 inductive discharges. Indeed, the resulting reactive species are crucial for the optimization of the Si-based etching process, since they determine the mechanisms of fluorination, polymerization, and sputtering. In this paper, we present the dissociation degree, the density ratio of F vs. CxFy (i.e., fluorocarbon (fc) neutrals), the neutral vs. positive ion density ratio, details on the neutral and ion components, and fractions of various fc neutrals (or ions) in the total fc neutral (or ion) density in a C4F8 inductively coupled plasma source, as well as the effect of pressure and power on these results. To analyze the fragmentation behavior, the electron density and temperature and electron energy probability function (EEPF) are investigated. Moreover, the main electron-impact generation sources for all considered neutrals and ions are determined from the complicated C4F8 reaction set used in the model. The C4F8 plasma fragmentation is explained, taking into account many factors, such as the EEPF characteristics, the dominance of primary and secondary processes, and the thresholds of dissociation and ionization. The simulation results are compared with experiments from literature, and reasonable agreement is obtained. Some discrepancies are observed, which can probably be attributed to the simplified polymer surface kinetics assumed in the model.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 11
DOI: 10.1063/1.4923230
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“Phase modulation in pulsed dual-frequency capacitively coupled plasmas”. Wen D-Q, Zhang Q-Z, Jiang W, Song U-H, Bogaerts A, Wang Y-N, Journal of applied physics 115, 233303 (2014). http://doi.org/10.1063/1.4884225
Abstract: Particle-in-cell/Monte Carlo collision simulations, coupled with an external circuit, are used to investigate the behavior of pulsed dual-frequency (DF) capacitively coupled plasmas (CCPs). It is found that the phase shift θ between the high (or low) frequency source and the pulse modulation has a great influence on the ion density and the ionization rate. By pulsing the high frequency source, the time-averaged ion density shows a maximum when θ = 90∘. The time-averaged ion energy distribution functions (IEDFs) at the driven electrode, however, keep almost unchanged, illustrating the potential of pulsed DF-CCP for independent control of ion density (and flux) and ion energy. A detailed investigation of the temporal evolution of the plasma characteristics indicates that several high frequency harmonics can be excited at the initial stage of a pulse period by tuning the phase shift θ, and this gives rise to strong sheath oscillations, and therefore high ionization rates. For comparison, the pulsing of the low frequency source is also studied. In this case, the ion density changes slightly as a function of time, and the time-averaged ion density shows the same trend as in the HF modulation for different phase shifts θ. Moreover, the time-averaged IEDFs at the driven electrode can be modulated, showing the potential to reduce the maximum ion bombardment energy.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 8
DOI: 10.1063/1.4884225
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“Understanding plasma catalysis through modelling and simulation : a review”. Neyts EC, Bogaerts A, Journal of physics: D: applied physics 47, 224010 (2014). http://doi.org/10.1088/0022-3727/47/22/224010
Abstract: Plasma catalysis holds great promise for environmental applications, provided that the process viability can be maximized in terms of energy efficiency and product selectivity. This requires a fundamental understanding of the various processes taking place and especially the mutual interactions between plasma and catalyst. In this review, we therefore first examine the various effects of the plasma on the catalyst and of the catalyst on the plasma that have been described in the literature. Most of these studies are purely experimental. The urgently needed fundamental understanding of the mechanisms underpinning plasma catalysis, however, may also be obtained through modelling and simulation. Therefore, we also provide here an overview of the modelling efforts that have been developed already, on both the atomistic and the macroscale, and we identify the data that can be obtained with these models to illustrate how modelling and simulation may contribute to this field. Last but not least, we also identify future modelling opportunities to obtain a more complete understanding of the various underlying plasma catalytic effects, which is needed to provide a comprehensive picture of plasma catalysis.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 130
DOI: 10.1088/0022-3727/47/22/224010
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“Understanding polyethylene surface functionalization by an atmospheric He/O2 plasma through combined experiments and simulations”. Dufour T, Minnebo J, Abou Rich S, Neyts EC, Bogaerts A, Reniers F, Journal of physics: D: applied physics 47, 224007 (2014). http://doi.org/10.1088/0022-3727/47/22/224007
Abstract: High density polyethylene surfaces were exposed to the atmospheric post-discharge of a radiofrequency plasma torch supplied in helium and oxygen. Dynamic water contact angle measurements were performed to evaluate changes in surface hydrophilicity and angle resolved x-ray photoelectron spectroscopy was carried out to identify the functional groups responsible for wettability changes and to study their subsurface depth profiles, up to 9 nm in depth. The reactions leading to the formation of CO, C = O and OC = O groups were simulated by molecular dynamics. These simulations demonstrate that impinging oxygen atoms do not react immediately upon impact but rather remain at or close to the surface before eventually reacting. The simulations also explain the release of gaseous species in the ambient environment as well as the ejection of low molecular weight oxidized materials from the surface.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 13
DOI: 10.1088/0022-3727/47/22/224007
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“Heating mode transition in a hybrid direct current/dual-frequency capacitively coupled CF4 discharge”. Zhang Q-Z, Wang Y-N, Bogaerts A, Journal of applied physics 115, 223302 (2014). http://doi.org/10.1063/1.4882297
Abstract: Computer simulations based on the particle-in-cell/Monte Carlo collision method are performed to study the plasma characteristics and especially the transition in electron heating mechanisms in a hybrid direct current (dc)/dual-frequency (DF) capacitively coupled CF 4 discharge. When applying a superposed dc voltage, the plasma density first increases, then decreases, and finally increases again, which is in good agreement with experiments. This trend can be explained by the transition between the four main heating modes, i.e., DF coupling, dc and DF coupling, dc source dominant heating, and secondary electron dominant heating.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 9
DOI: 10.1063/1.4882297
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“Modeling ultrashort laser-induced emission from a negatively biased metal”. Wendelen W, Mueller BY, Autrique D, Bogaerts A, Rethfeld B, Applied physics letters 103, 221603 (2013). http://doi.org/10.1063/1.4830378
Abstract: A theoretical study of ultrashort laser-induced electron emission from a negatively biased metallic cathode has been performed. Classical as well as tunneling electron emission mechanisms are considered. It was found that electron emission is governed by an interplay of processes inside as well as above the cathode. A hybrid model is proposed, where the electron distribution within the target is retrieved from Boltzmann scattering integrals, while the charge distribution above it is studied by a Particle-In-Cell simulation. The results indicate that non-equilibrium effects determine the initial emission process, whereas the space charge above the target suppresses the effectively emitted charge.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.411
Times cited: 8
DOI: 10.1063/1.4830378
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“The essential role of the plasma sheath in plasma–liquid interaction and its applications—A perspective”. Vanraes P, Bogaerts A, Journal Of Applied Physics 129, 220901 (2021). http://doi.org/10.1063/5.0044905
Abstract: Based on the current knowledge, a plasma–liquid interface looks and behaves very differently from its counterpart at a solid surface. Local processes characteristic to most liquids include a stronger evaporation, surface deformations, droplet ejection, possibly distinct mechanisms behind secondary electron emission, the formation of an electric double layer, and an ion drift-mediated liquid resistivity. All of them can strongly influence the interfacial charge distribution. Accordingly, the plasma sheath at a liquid surface is most likely unique in its own way, both with respect to its structure and behavior. However, insights into these properties are still rather scarce or uncertain, and more studies are required to further disclose them. In this Perspective, we argue why more research on the plasma sheath is not only recommended but also crucial to an accurate understanding of the plasma–liquid interaction. First, we analyze how the sheath regulates various elementary processes at the plasma–liquid interface, in terms of the electrical coupling, the bidirectional mass transport, and the chemistry between plasma and liquid phase. Next, these three regulatory functions of the sheath are illustrated for concrete applications. Regarding the electrical coupling, a great deal of attention is paid to the penetration of fields into biological systems due to their relevance for plasma medicine, plasma agriculture, and food processing. Furthermore, we illuminate the role of the sheath in nuclear fusion, nanomaterial synthesis, and chemical applications. As such, we hope to motivate the plasma community for more fundamental research on plasma sheaths at liquid surfaces.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 2.068
DOI: 10.1063/5.0044905
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“Special issue on fundamentals of plasmasurface interactions”. Bogaerts A, Neyts EC, Rousseau A, Journal of physics: D: applied physics 47, 220301 (2014). http://doi.org/10.1088/0022-3727/47/22/220301
Keywords: Editorial; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 2
DOI: 10.1088/0022-3727/47/22/220301
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“Plasma propagation in a single bead DBD reactor at different dielectric constants : insights from fluid modelling”. Wang W, Butterworth T, Bogaerts A, Journal Of Physics D-Applied Physics 54, 214004 (2021). http://doi.org/10.1088/1361-6463/ABE8FF
Abstract: Packed bed dielectric barrier discharge (PB-DBD) plasma reactors are very promising for various plasma catalysis applications, but the exact mechanisms of plasma-catalyst interaction are far from understood, because the plasma discharge and catalyst/packing properties are mutually dependent. To better understand the effect of packing dielectric material on the electrical plasma properties, we study here a single bead DBD plasma reactor operating in dry air, with beads of different dielectric constant and for different applied voltages, by means of fluid modelling validated by optical imaging experiments. Our study reveals that the plasma in the single bead DBD reactor can manifest itself in two different modalities, i.e. (a) polar discharges at the bead poles in contact with the electrodes, and (b) a streamer discharge caused by surface ionization waves, which bridges the gas gap. Beads with high dielectric constant result in localised electric field enhancement and hence yield a reduction of the applied voltage required for plasma production. At low applied voltage, the discharge appears as polar discharges between the bead and the electrodes, and upon higher voltage it undergoes a transition into a bridging streamer discharge. The transition voltage to the streamer mode rises for beads with higher dielectric constant. These observations are important for plasma catalysis applications. A higher dielectric constant yields a higher electric field and thus higher average electron energy and density, giving rise to more reactive species, but it also yields a confined discharge near the contact points of packing beads, limiting the interaction area between the catalyst and the active plasma species. In addition, our model reveals that the dielectric bead behaves as a capacitor and traps charges, which can explain the significant occurrence of partial discharging in PB-DBDs and non-parallelogram shaped Lissajous plots. Hence, equivalent circuit modelling of PB-DBDs should take into account the role of packing beads in charge trapping as a capacitor.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
DOI: 10.1088/1361-6463/ABE8FF
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“Fluid modelling of an atmospheric pressure dielectric barrier discharge in cylindrical geometry”. Petrović, D, Martens T, van Dijk J, Brok WJM, Bogaerts A, Journal of physics: D: applied physics 42, 205206 (2009). http://doi.org/10.1088/0022-3727/42/20/205206
Abstract: A numerical parameter study has been performed for a cylindrical atmospheric pressure dielectric barrier discharge (DBD) in helium with nitrogen impurities using a two-dimensional time-dependent fluid model. The calculated electric currents and gap voltages as a function of time for a given applied potential are presented, as well as the number densities of the various plasma species. This study shows that for the geometry under consideration the applied voltage parameters have a large impact on the electric current profiles and that the discharge current is always determined by the electron and ion conduction currents while the displacement current is nearly negligible. A relative broadening of the current profiles (compared with the duration of the half cycle of the applied voltage) with an increase in the applied frequency is obtained. Nearly sinusoidal current wave forms, usually typical for radio frequency DBDs, are observed while still operating at the frequencies of tens of kilohertz. For the setup under investigation, the Townsend mode of the DBD is observed in the entire range of applied voltage amplitudes and frequencies. It is shown that the average power density dissipated in the discharge increases with rising applied voltage and frequency. An increase in applied voltage frequency leads to an increase in the electron density and a decrease in electron energy, while increasing the voltage amplitude has the opposite effect.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 29
DOI: 10.1088/0022-3727/42/20/205206
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“Spatially resolved ozone densities and gas temperatures in a time modulated RF driven atmospheric pressure plasma jet : an analysis of the production and destruction mechanisms”. Zhang S, Van Gaens W, van Gessel B, Hofmann S, van Veldhuizen E, Bogaerts A, Bruggeman P, Journal of physics: D: applied physics 46, 205202 (2013). http://doi.org/10.1088/0022-3727/46/20/205202
Abstract: In this work, a time modulated RF driven DBD-like atmospheric pressure plasma jet in Ar + 2%O2, operating at a time averaged power of 6.5 W is investigated. Spatially resolved ozone densities and gas temperatures are obtained by UV absorption and Rayleigh scattering, respectively. Significant gas heating in the core of the plasma up to 700 K is found and at the position of this increased gas temperature a depletion of the ozone density is found. The production and destruction reactions of O3 in the jet effluent as a function of the distance from the nozzle are obtained from a zero-dimensional chemical kinetics model in plug flow mode which considers relevant air chemistry due to air entrainment in the jet fluent. A comparison of the measurements and the models show that the depletion of O3 in the core of the plasma is mainly caused by an enhanced destruction of O3 due to a large atomic oxygen density.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 74
DOI: 10.1088/0022-3727/46/20/205202
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“Investigating the plasma chemistry for the synthesis of carbon nanotubes/nanofibres in an inductively coupled plasma enhanced CVD system : the effect of different gas mixtures”. Mao M, Bogaerts A, Journal of physics: D: applied physics 43, 205201 (2010). http://doi.org/10.1088/0022-3727/43/20/205201
Abstract: A hybrid model, called the hybrid plasma equipment model (HPEM), was used to study an inductively coupled plasma in gas mixtures of H2 or NH3 with CH4 or C2H2 used for the synthesis of carbon nanotubes or carbon nanofibres (CNTs/CNFs). The plasma properties are discussed for different gas mixtures at low and moderate pressures, and the growth precursors for CNTs/CNFs are analysed. It is found that C2H2, C2H4 and C2H6 are the predominant molecules in CH4 containing plasmas besides the feedstock gas, and serve as carbon sources for CNT/CNF formation. On the other hand, long-chain hydrocarbons are observed in C2H2-containing plasmas. Furthermore, the background gases CH4 and C2H2 show a different decomposition rate with H2 or NH3 addition at moderate pressures.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 52
DOI: 10.1088/0022-3727/43/20/205201
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“Modelling of plasma-based dry reforming: how do uncertainties in the input data affect the calculation results?”.Wang W, Berthelot A, Zhang Q, Bogaerts A, Journal of physics: D: applied physics 51, 204003 (2018). http://doi.org/10.1088/1361-6463/aab97a
Abstract: One of the main issues in plasma chemistry modeling is that the cross sections and rate coefficients are subject to uncertainties, which yields uncertainties in the modeling results and hence hinders the predictive capabilities. In this paper, we reveal the impact of these uncertainties on the model predictions of plasma-based dry reforming in a dielectric barrier discharge. For this purpose, we performed a detailed uncertainty analysis and sensitivity study. 2000 different combinations of rate coefficients, based on the uncertainty from a log-normal distribution, are used to predict the uncertainties in the model output. The uncertainties in the electron density and electron temperature are around 11% and 8% at the maximum of the power deposition for a 70% confidence level. Still, this can have a major effect on the electron impact rates and hence on the calculated conversions of CO2 and CH4, as well as on the selectivities of CO and H2. For the CO2 and CH4 conversion, we obtain uncertainties of 24% and 33%, respectively. For the CO and H2 selectivity, the corresponding uncertainties are 28% and 14%, respectively. We also identify which reactions contribute most to the uncertainty in the model predictions. In order to improve the accuracy and reliability of plasma chemistry models, we recommend using only verified rate coefficients, and we point out the need for dedicated verification experiments.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 7
DOI: 10.1088/1361-6463/aab97a
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Mannaerts D, Faes E, Cos P, Briedé, JJ, Gyselaers W, Cornette J, Gorbanev Y, Bogaerts A, Spaanderman M, Van Craenenbroeck E, Jacquemyn Y, Torrens C (2018) Oxidative stress in healthy pregnancy and preeclampsia is linked to chronic inflammation, iron status and vascular function. e0202919
Abstract: Background
During normal pregnancy, placental oxidative stress (OS) is present during all three trimesters and is necessary to obtain normal cell function. However, if OS reaches a certain level, pregnancy complications might arise. In preeclampsia (PE), a dangerous pregnancy specific hypertensive disorder, OS induced in the ischemic placenta causes a systemic inflammatory response and activates maternal endothelial cells. In this study, we aimed to quantify superoxide concentrations (as a measure of systemic OS) using electron paramagnetic resonance (EPR) and correlate them to markers of systemic inflammation, iron status and vascular function.
Methods
Fifty-nine women with a healthy pregnancy (HP), 10 non-pregnant controls (NP) and 28 PE patients (32±3.3weeks) were included. During HP, blood samples for superoxide, neutrophil to lymphocyte ratio (NLR), mean platelet volume (MPV) and iron status were taken at 10, 25 and 39 weeks. Vascular measurements for arterial stiffness (carotid-femoral pulse wave velocity (CF-PWV), augmentation index (AIx), augmentation Pressure (AP)) and microvascular endothelial function (reactive hyperemia index (RHI)) were performed at 35 weeks. In PE, all measurements were performed at diagnosis. CMH (1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine) was used as spin probe for EPR, since the formed CM radical
corresponds to the amount of superoxide.
Results
Superoxide concentration remains stable during pregnancy (p = 0.92), but is significantly higher compared to the NP controls (p<0.0001). At 25 weeks, there is a significant positive correlation between superoxide and ferritin concentration. (p = 0.04) In PE, superoxide, systemic inflammation and iron status are much higher compared to HP (all p<0.001). During HP, superoxide concentrations correlate significantly with arterial stiffness (all p<0.04), while in PE superoxide is significantly correlated to microvascular endothelial function (p = 0.03).
Conclusions
During HP there is an increased but stable oxidative environment, which is correlated to ferritin concentration. If superoxide levels increase, there is an augmentation in arterial stiffness. In PE pregnancies, systemic inflammation and superoxide concentrations are higher and result in a deterioration of endothelial function. Together, these findings support the hypothesis that vascular function is directly linked to the amount of OS and that measurement of OS in combination with vascular function tests might be used in the prediction of PE.
Keywords: University Hospital Antwerp; A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Antwerp Surgical Training, Anatomy and Research Centre (ASTARC); Translational Pathophysiological Research (TPR)
Impact Factor: 2.806
Times cited: 15
DOI: 10.1371/journal.pone.0202919
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“The effect of the magnetic field strength on the sheath region of a dc magnetron discharge”. Bultinck E, Bogaerts A, Journal of physics: D: applied physics 41, 202007 (2008). http://doi.org/10.1088/0022-3727/41/20/202007
Abstract: A 2d3v particle-in-cell/Monte Carlo collisions model was applied to study the influence of the magnetic field strength on the cathode sheath region of a direct current (dc) magnetron discharge. When applying a magnetic field of 520-730 G, the cathode sheath width decreases with magnetic field strength, whereas, if a stronger magnetic field is applied (i. e. from 730 to 2600 G), the sheath width increases. This is explained by studying the structure of the sheath in different magnetic field strengths in terms of the electron and ion densities. The consequences of sheath structure on the sputter deposition process are also investigated. It is found that the magnetic field strength can control the erosion profile and the sputter rate.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 16
DOI: 10.1088/0022-3727/41/20/202007
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“Plasma–liquid interactions”. Bruggeman PJ, Bogaerts A, Pouvesle JM, Robert E, Szili EJ, Journal Of Applied Physics 130, 200401 (2021). http://doi.org/10.1063/5.0078076
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 2.068
DOI: 10.1063/5.0078076
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“Computational study of the CF4 /CHF3 / H2 /Cl2 /O2 /HBr gas phase plasma chemistry”. Tinck S, Bogaerts A, Journal of physics: D: applied physics 49, 195203 (2016). http://doi.org/10.1088/0022-3727/49/19/195203
Abstract: A modelling study is performed of high-density low-pressure inductively coupled CF4/CHF3/H2/Cl2/O2/HBr plasmas under different gas mixing ratios. A reaction set describing the complete plasma chemistry is presented and discussed. The gas fraction of each component in this mixture is varied to investigate the sensitivity of the plasma properties, like electron density, plasma potential and species densities, towards the gas mixing ratios. This research is of great interest for microelectronics applications because these gases are often combined in two (or more)-component mixtures, and mixing gases or changing the fraction of a gas can sometimes yield unwanted reaction products or unexpected changes in the overall plasma properties due to the increased chemical complexity of the system. Increasing the CF4 fraction produces more F atoms for chemical etching as expected, but also more prominently lowers the density of Cl atoms, resulting in an actual drop in the etch rate under certain conditions. Furthermore, CF4 decreases the free electron density when mixed with Cl2. However, depending on the other gas components, CF4 gas can also sometimes enhance free electron density. This is the case when HBr is added to the mixture. The addition of H2 to the gas mixture will lower the sputtering process, not only due to the lower overall positive ion density at higher H2 fractions, but also because more H+, H2 + and H3 + are present and they have very low sputter yields. In contrast, a larger Cl2 fraction results in more chemical etching but also in less physical sputtering due to a smaller abundance of positive ions. Increasing the O2 fraction in the plasma will always lower the etch rate due to more oxidation of the wafer surface and due to a lower plasma density. However, it is also observed that the density of F atoms can actually increase with rising O2 gas fraction. This is relevant to note because the exact balance between fluorination and oxidation is important for fine-tuning the overall etch rate and for control of the sidewall profile. Finally, HBr is often used as a chemical etcher, but when mixed with F- or Cl-containing gases, HBr creates the same diluting effects as Ar or He, because a
higher fraction results in less chemical etching but more (physical) sputtering.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 5
DOI: 10.1088/0022-3727/49/19/195203
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“Computer modelling of magnetron discharges”. Bogaerts A, Bultinck E, Kolev I, Schwaederlé, L, van Aeken K, Buyle G, Depla D, Journal of physics: D: applied physics 42, 194018 (2009). http://doi.org/10.1088/0022-3727/42/19/194018
Abstract: In this paper, some modelling approaches to describe direct current (dc) magnetron discharges developed in our research groups will be presented, including an analytical model, Monte Carlo simulations for the electrons and for the sputtered atoms, a hybrid Monte Carlo-fluid model and particle-in-cell-Monte Carlo collision simulations. The strengths and limitations of the various modelling approaches will be explained, and some characteristic simulation results will be illustrated. Furthermore, some other simulation methods related to the magnetron device will be briefly explained, more specifically for calculating the magnetic field distribution inside the discharge, and for describing the (reactive) sputtering.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 32
DOI: 10.1088/0022-3727/42/19/194018
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“Computational study of plasma sustainability in radio frequency micro-discharges”. Zhang Y, Jiang W, Zhang QZ, Bogaerts A, Journal of applied physics 115, 193301 (2014). http://doi.org/10.1063/1.4878161
Abstract: We apply an implicit particle-in-cell Monte-Carlo (PIC-MC) method to study a radio-frequency argon microdischarge at steady state in the glow discharge limit, in which the microdischarge is sustained by secondary electron emission from the electrodes. The plasma density, electron energy distribution function (EEDF), and electron temperature are calculated in a wide range of operating conditions, including driving voltage, microdischarge gap, and pressure. Also, the effect of gap size scaling (in the range of 50-1000 μm) on the plasma sustaining voltage and peak electron density at atmospheric pressure is examined, which has not been explored before. In our simulations, three different EEDFs, i.e., a so-called three temperature hybrid mode, a two temperature α mode, and a two temperature γ mode distribution, are identified at different gaps and voltages. The maximum sustaining voltage to avoid a transition from the glow mode to an arc is predicted, as well as the minimum sustaining voltage for a steady glow discharge. Our calculations elucidate that secondary electrons play an essential role in sustaining the discharge, and as a result the relationship between breakdown voltage and gap spacing is far away from the Paschen law at atmospheric pressure.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 11
DOI: 10.1063/1.4878161
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“Plasma modelling and numerical simulation”. van Dijk J, Kroesen GMW, Bogaerts A, Journal of physics: D: applied physics 42, 190301 (2009). http://doi.org/10.1088/0022-3727/42/19/190301
Abstract: Plasma modelling is an exciting subject in which virtually all physical disciplines are represented. Plasma models combine the electromagnetic, statistical and fluid dynamical theories that have their roots in the 19th century with the modern insights concerning the structure of matter that were developed throughout the 20th century. The present cluster issue consists of 20 invited contributions, which are representative of the state of the art in plasma modelling and numerical simulation. These contributions provide an in-depth discussion of the major theories and modelling and simulation strategies, and their applications to contemporary plasma-based technologies. In this editorial review, we introduce and complement those papers by providing a bird's eye perspective on plasma modelling and discussing the historical context in which it has surfaced.
Keywords: Editorial; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 64
DOI: 10.1088/0022-3727/42/19/190301
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