Coplanar Dielectric Barrier Discharge Research Articles

Characteristics and performance of an integrated coplanar dielectric barrier discharge device for hand hygiene

AbstractA touchable plasma device based on coplanar dielectric barrier discharge (CDBD) is designed for hand hygiene. The biological safety is evaluated from the aspects of electrical and thermal properties. The peak value of current through the human body (~3.5 mA) and the highest device surface temperature (~40°C) are lower than the threshold of perception current and thermal damage temperature, respectively. The typical bacteria that are present on our hands in daily life Escherichia coli and Staphylococcus aureus are selected to verify the sterilization performance of the device. The results of human contact safety evaluation and sterilization test have demonstrated that this proposed CDBD device is reliable and user‐friendly for applications in hand hygiene.

Characterization of a co-planar dielectric barrier discharge design as a plasma source for trace element detection by atomic spectrometry

Dielectric barrier discharges (DBD) are used in analytical chemistry for the dissociation of molecules, which can then be detected with methods like atomic absorption spectroscopy or emission spectroscopy. However, a drawback of this approach is that the analyte can be deposited on the reactor walls, lowering the density available for element detection. In this work, we propose a novel design of a DBD for element detection which consists of a T-shaped quartz glass body with line-shaped co-planar electrodes. This co-planar configuration was selected to force the discharge towards the glass surface, thus increasing the release of deposited analyte from the reactor walls. This was verified by temporally and spatially resolved optical emission spectroscopy showing that the plasma propagates in a bent structure, close to the wall between the electrodes. The optical results also point towards the importance of helium metastable states in the dissociation of molecules. Thus, spatially resolved metastable densities were measured by tunable diode laser absorption spectroscopy. The metastable density was in the order of 4.5×1010cm−3, and the density profile correlated with the bent structure observed in the emission measurements.

Influence of Gas Temperature on Gaseous Products Generated by Coplanar Barrier Discharge in Air and N2/O2 Mixtures

Absolute densities of gaseous products generated by coplanar dielectric barrier discharge in N2/O2 mixtures and in ambient air were determined by UV optical absorption spectroscopy (OAS). Ozone (O3) and nitrogen oxides (N2O, NO2 and N2O5) were identified as the stable products of the discharge. It was found that the actual product composition strongly depends on the gas temperature. At low input power with the low gas temperature, O3 density was high and the NO2 density was very low. When the input power increased and the gas temperature also increased, then O3 disappeared, while NO2 density started to increase steeply.

Experimental Investigation on Atmospheric Pressure Plasma Jet under Locally Divergent Magnet Field

Regulating the parameters of the atmospheric pressure plasma jet (APPJ) is meaningful for industrial applications. Since plasma is a typical functional fluid in the magnetic field, it is possible to control the discharge characteristics via the Lorentz force. In this study, the effects of a locally divergent magnetic field on the generation and propagation of APPJ were examined experimentally. The experiments used a coplanar dielectric barrier discharge (CDBD) device driven by a 30 kHz AC high-voltage source to generate a helium APPJ. A locally divergent magnetic field of 250 mT (maximum) was applied coupled with the electric field, and noticeable enhancement was observed. The results showed that the magnetic field changed the motion state of electrons and promoted collision ionization, leading to a 40% improvement in the APPJ length (0.6 cm) and a 23% increase in the intensity of line O (777.2 nm). In addition, the spatiotemporal evolution and flow field of APPJ were diagnosed by ICCD and schlieren technique. The combination of electric and magnetic fields may effectively optimize the APPJ in practical applications.

Modified equivalent circuit for coplanar dielectric barrier discharge considering undischarged areas

Coplanar dielectric barrier discharge has a wide range of potential applications in the domains of material surface modification and other areas by producing a thin layer of diffuse plasma with high power density in the air. For a thorough examination of essential variables and discharge properties of coplanar dielectric barrier discharge plasma, an equivalent circuit model is essential. In this paper, a modified equivalent circuit for coplanar dielectric barrier discharge (CDBD) that took into account both the undischarged part and the parasitic capacitance was developed and discussed. The results showed that in the diffusion phase, the discharge area fraction grew quickly with voltage and caused a significant drop in plasma impedance and burning voltage. As the applied voltage increased, the discharge area fraction tended to saturate, the burning voltage slowly rose, and a lot of micro-discharges with greater diameters were present on the dielectric surface during the saturation phase.

Chemical composition of gaseous products generated by coplanar barrier discharge in air and N2/O2 mixtures

Absolute densities of gaseous products generated by coplanar dielectric barrier discharge in N2/O2 mixtures and in ambient air were determined using Fourier transform infrared (FTIR) spectroscopy. A theoretical model containing up to four molecular absorption cross sections was used to split the peaks overlapping in the FTIR spectra. The product densities were determined for a wide range of applied input powers (100–400 W). Ozone (O3) and nitrogen oxides (N2O, NO, NO2 and N2O5) were identified as the stable products of the discharge in N2/O2 mixtures, HNO2, HNO3 and CO2 were steadily present in the gas coming from the discharge in ambient air. It was found that the actual product composition strongly depends on the gas temperature. At low input power with the low gas temperature, O3 density was high and the NO and NO2 densities were very low. At a specific input power (and the gas temperature) O3 disappeared, while NO density started to increase gradually and NO2 density increased steeply. N2O5 density increased at low input power but decreased suddenly at the same temperature when O3 density decreased. The influence of the gas temperature on the discharge product composition was also confirmed by the 0D chemical kinetic model and by temperature measurement. The maximal ozone density reached approximately 2.7 × 1023 m−3 for the input power below 150 W and the gas mixture N2:O2 40:60. Density of 2.6 × 1022 m−3 was obtained for NO2 in the same gas mixture above 250 W.

Large‐area open air plasma sources for roll‐to‐roll manufacture

SummaryThe aim of the current paper is to introduce technology for the generation of high‐power density surface plasma by a diffuse coplanar surface barrier discharge (DCSBD) plasma unit. The diffuse and uniform plasma generated in low‐cost gases such as open air enables easy integration into novel or existing roll‐to‐roll (R2R) lines. We briefly discuss the history of the development of dielectric barrier discharges (DBDs) toward the most advanced plasma sources based on the coplanar arrangement of electrodes. Moreover, we present and discuss the advantages and disadvantages of the effect of volume and coplanar DBD treatments performed in R2R mode on the surface of polyamide. The paper also discusses the potential of R2R plasma treatments for next‐generation applications of novel flexible and printed electronics.

The Effect of Non-Thermal Atmospheric Pressure Plasma Treatment of Wheat Seeds on Germination Parameters and α-Amylase Enzyme Activity

This contribution presents the results of a study of the germination rate and growth parameters of wheat seeds after atmospheric pressure surface coplanar dielectric barrier discharge (DBD) plasma treatment. The germination rate and biometric parameters such as the root, shoot length, mass of the seedlings, and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -amylase enzyme activity were studied at different plasma exposure time. The seed coat surface wettability and morphology were determined by apparent contact angle measurement and scanning electron microscope (SEM) analysis. Seed surface disinfection and the presence of filamentous fungi have also been investigated at different discharge parameters. It is shown that the optimal plasma treatment duration for increasing the growth parameters and enhancing the enzymatic activity is 5–15 s. It was found that the longer plasma exposure requires complete sterilization of the seed surface from pathogens, compared to the optimal treatment time for high germination. Based on the obtained results, the possible mechanisms of the positive effect of plasma treatment on the enhanced germination of wheat seeds are discussed.

Changes in Surface Characteristics of BOPP Foil after Treatment by Ambient Air Plasma Generated by Coplanar and Volume Dielectric Barrier Discharge.

Biaxially oriented polypropylene (BOPP) is a highly transparent polymer defined by excellent mechanical and barrier properties applicable in the food packaging industry. However, its low surface free energy restricts its use in many industrial processes and needs to be improved. The presented study modifies a BOPP surface using two different atmospheric-pressure plasma sources operating in ambient air and capable of inline processing. The volume dielectric barrier discharge (VDBD) and diffuse coplanar surface barrier discharge (DCSBD) were applied to improve the wettability and adhesion of the 1–10 s treated surface. The changes in morphology and surface chemistry were analyzed by SEM, AFM, WCA/SFE, and XPS, and adhesion was evaluated by a peel force test. Comparing both plasma sources revealed their similar effect on surface wettability and incorporation of polar functional groups. Additionally, higher surface roughness in the case of VDBD treatment contributed to slightly more efficient adhesion in comparison to DCSBD. Although we achieved comparable results for both plasma sources in the term of enhanced surface wettability, degree of oxidation, and stability of induced changes, DCSBD had less effect on the surface deterioration than VDBD, where surface structuring caused an undesirable haze.

The effect of ambient air plasma generated by coplanar and volume dielectric barrier discharge on the surface characteristics of polyamide foils

This study targeted wettability and adhesion enhancement of polyamide (PA) foil surface by plasma treatment at atmospheric pressure. Volume dielectric barrier discharge (VDBD) and diffuse coplanar surface barrier discharge (DCSBD) were applied in ambient air using exposure times 0.25–2 s. Water contact angle (WCA) measurements proved that both plasma sources achieved significant wettability improvement of PA 6 foil surface immediately after treatment. However, the durability of this hydrophilic effect was much more pronounced with the DCSBD, compared to the VDBD. The lowest registered drop of WCA after DCSBD treatment was from the initial 65° to 28°, which even after one month of storage recovered only to 44°. In contrast, the VDBD treatment at similar parameters resulted in the WCA increase from 45° to 54° already after the first day of ageing. The XPS analysis of oxygen-based polar functional groups incorporated onto the treated PA 6 surface proved higher efficiency of DCSBD plasma. Moreover, the degree of surface oxidation was raised by increasing DCSBD's input power. Tape peel test revealed adhesion improvement achieved only with DCSBD, which had a growing tendency with increasing exposure time and input power. SEM did not show any noticeable damage of surface after the applied plasma treatments.

Properties of MgAl2O4 doped alumina barrier layers for dielectric barrier discharge

In the current work, we studied the effect of multiphasic dielectric material on coplanar dielectric barrier discharge. To enhance the application potential of standard alumina () ceramic barriers, composite materials composed of immiscible and Mg-spinel () phases were prepared and investigated. The effect on coplanar dielectric barrier discharge was studied in a broad concentration profile of the composite materials ranging from 0 to 100 vol.% in an alumina matrix. The study was mainly focused on the determination of ignition voltage as a crucial parameter for industrial applications. The minimum ignition voltage was found in the ceramic composite with 15 vol.% . We also noticed differences in plasma filament localization on the ceramic surfaces of different composites. This work also brings comprehensive investigation of the electrical and microstructural properties of this biphasic barrier material. Detailed investigation revealed that the ignition voltage was a nontrivial combination of both bulk (phase and chemical compositions) as well as surface (phase distribution, grain size, surface roughness) properties of the barrier materials.

Modification of powders by atmospheric pressure plasma and embedding into nickel coatings

The aim of this work was to achieve improved dispersibility of hydrophobic dry lubricants in aqueous media through plasma activation. As a result, the use of wet-chemical environmentally questionable substances – for example, certain surfactants – to ensure the dispersibility of such particles can be avoided. These plasma-activated particles can be further embedded in electroless nickel (Ni) coatings to improve wear behaviour. Thus, the hydrophobic polymeric powders polyimide and polyetheretherketone and the ceramic powder hexagonal boron nitride (BN) were activated with atmospheric pressure plasma using a diffuse coplanar dielectric barrier discharge system. The generation of polar chemical bonds on the powder surface resulted in an improved dispersibility of the powders in aqueous media. This led to a higher deposit volume of the particles in electroless nickel dispersion coatings. The modified bonding conditions at the powder surfaces were analysed with infrared and X-ray photoelectron spectroscopy. Optical microscopy and scanning electron microscopy investigations showed the deposit of the activated dispersed phase in the coatings. Furthermore, the wear behaviour of the coating was tested by using the Taber abraser test. The plasma activation led to surface modifications – namely, linkage of polar groups at the powder surfaces – and therefore to improved dispersibility. The deposition of the particles in the electroless nickel coatings was possible with all three materials, and the wear resistance of the coatings was improved.

Study of large-area atmospheric pressure plasma jet based on coplanar dielectric barrier discharge

<p indent="0mm">In order to obtain a uniform large-area plasma jet at the atmospheric pressure, a new structure of coplanar dielectric barrier discharge (DBD) is proposed in this paper. The structure used in large-area DBD plasma jet consists of two coaxial annular dielectric tubes, and an alternating current electric field is applied by metal film electrodes outside the tubes to form dielectric barrier discharge in the air gap. Based on this configuration, a uniform annular jet is achieved, with diameter of <sc>12 mm</sc> and thickness of <sc>2–3 mm.</sc> The discharge characteristics of the proposed structure and the development process of plasma jet are studied. The spectra of the discharge, the electron temperature, the electron density, and the discharge waveforms are diagnosed. The results show that the physical characteristics of the large-area jet obtained in this work are basically the same as that of the traditional small-diameter DBD jet. It is considered that the physical mechanism of the large-area jet propagation is the mutual coupling propulsion process of a large number of positive corona discharges. The influence of electrode structure and air gap structure on the characteristics of the large-area DBD plasma jet is further studied by experiments, and the optimization principle of the large-area DBD plasma jet is proposed.

Preparation and characterization of alumina submicron fibers by plasma assisted calcination

Ceramic alumina nanofibers were prepared by plasma-assisted calcination (PAC) using atmospheric pressure plasma. Electrospun polyvinyl pyrrolidone/aluminium butoxide fibers were pre-treated by plasma generated in ambient air using a special type of coplanar dielectric barrier discharge. The effect of plasma on fibers and structural, chemical and crystalline properties of obtained ceramic nanofibers were characterized using X-Ray Photoelectron Spectroscopy and Scanning Electron Microscopy, Energy-dispersive X-ray Spectroscopy and X-Ray Diffraction. Thermogravimetric and differential thermal analysis were used for the study of thermal behaviour of untreated and plasma-treated samples. The ceramic fibers prepared by PAC exhibit suitable chemical composition, higher porosity, high length of fibers and better crystalline properties with simultaneous simplifying of the sintering process. The plasma pre-treatment of fibers results in a shortening of following thermal treatment, decrease of the required temperature and excludes a slow temperature increase as prevention of fibrous structure degradation typical in preparation of ceramic fibers by polymer-template techniques.

On the inactivation of Bacillus subtilis spores by surface streamer discharge in humid air caused by reactive species

The inactivation of Bacillus subtilis (ATCC 6633) spores deposited on a filter membrane was studied by using low-temperature plasma produced via surface dielectric barrier discharge. Spore samples were carefully prepared to avoid the formation of cell aggregates, and their inactivation was induced by multiple surface streamer discharge driven in a coplanar dielectric barrier discharge electrode geometry by an amplitude-modulated AC high voltage waveforms in humid air at atmospheric pressure. At a discharge duty cycle of 0.4, the surface dielectric barrier discharge is characterised by an average total power of 1.7 W (power density 1.5 W cm−2 and energy density ∼0.3 Wh l−1) and a low gas temperature of the plasma filaments of about 320 K. The spores were exposed by placing a sample holder at a fixed distance of 3 mm from the electrode surface covered by plasma filaments. Particular attention was paid to identifying sporicidal agents employed in the process of inactivation. Since treated samples did not come into direct contact with the streamer filaments and excessive heating was excluded thanks to the low energy density, our results indicate that the spores were inactivated mainly by reactive oxygen and nitrogen species such as O3, H2O2 and NO2–. Discharge-induced damage of the spore structure was evidenced via the detection of dipicolinic acid and leaking of intracellular components. We therefore conclude that B. subtilis spores were inactivated chemically, probably due to failure of the coat structure or membrane of the spore.

Efficiency of Ozone Production in Coplanar Dielectric Barrier Discharge

Efficient generation of ozone by cold atmospheric plasmas is interesting for sterilisation and decontamination of thermally-sensitive surfaces. This paper presents a study of robust coplanar dielectric barrier discharge (DBD) for generating atmospheric pressure plasma in synthetic air and in oxygen. The atmospheric plasma generated by coplanar DBD in synthetic air showed considerably high ozone production of 2.41 g/h (2.25 slm, 45 W), while the production yield and energy cost were 54 g/kWh and 40.9 eV/molecule. The use of oxygen instead of synthetic air, at much lower discharge power (2.25 slm, 17 W), maintained the ozone production of 2.35 g/h, whereas the production yield significantly increased to 138 g/kWh with a corresponding energy cost of 12.9 eV/molecule. The temperature of coplanar DBD ceramics in synthetic air (45 W) and oxygen (17 W) plasma generation (continuous alternating-current operation) showed temperatures below 70 °C and 30 °C, respectively. The rotational temperatures obtained from optical emission spectroscopy indicated similar gas temperatures in the thin plasma layer close to the surface of the DBD ceramics. The low temperature of the plasma–ceramics interface evidences the applicability of coplanar DBD for the contact treatment of thermally sensitive surfaces where a high concentration of ozone is required.

A Comparison of the Effects of Ambient Air Plasma Generated by Volume and by Coplanar DBDs on the Surfaces of PP/Al/PET Laminated Foil

This contribution presents a comparison of the effects of atmospheric-pressure plasma in ambient air on the surface properties of polypropylene/aluminum/polyethylene terephthalate (PP/Al/PET) laminated foil. Plasma treatment was applied by means of two types of ambient-air dielectric-barrier discharge (DBD): 1) coplanar DBD and 2) volume DBD. The surface energy levels of the PP and PET surfaces terms were measured. The morphology and surface chemistry of the PP and PET surfaces were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The differences in the effect of coplanar and volume DBDs on polymer surfaces are observed and explained in terms of the properties of microdischarges in coplanar and volume DBDs. The influence of the Al interlayer on plasma behavior is discussed.

Tuning the water-alumina nanofluids impedance and dielectric relaxation by the diffuse coplanar dielectric barrier discharge

Nanofluids are nowadays representing an exciting tool with significant impact and tremendous potential in several industrial applications. In the present paper, we focus our attention on the tunability of the electrical and dielectric properties of alumina nanoparticle-based nanofluids achieved by preliminary modifying the particle surface charging by a diffuse coplanar dielectric barrier discharge plasma treatment. We produced a parametric study on the tuning of the plasma-treatedalumina-based nanofluid electrical response as a function of the selected discharge feeding gases.

Mineralization of flexible mesoporous TiO2 photoanodes using two low-temperature dielectric barrier discharges in ambient air

Two types of dielectric barrier discharges (DBDs), volume DBD (called Industrial Corona) and coplanar DBD, were used for low temperature (70 degrees C) atmospheric pressure plasma mineralization of mesoporous methyl-silica/titanium dioxide nanocomposite photoanodes. The photoanodes with a thickness of approx. 300 nm were inkjet-printed on flexible polyethylene terephthalate (PET) foils. Plasma treatments of both DBDs led to changes in the chemical stoichiometry and morphology of the mesoporous photoanodes, resulting in a significant increase of the work function from approx. 4.0 to 4.3 eV and 4.8 eV, after plasma mineralization with volume DBD and coplanar DBD, respectively. We also studied the effect of plasma mineralization on the photoelectrochemical properties of the flexible mesoporous TiO2 photoanodes. Plasma mineralization with volume DBD and coplanar DBD showed different effects on the generated photocurrent in the photoanodes. Although the plasma mineralization with volume DBD showed only a minor effect on the photocurrent, plasma mineralization with coplanar DBD led to significantly higher photocurrents. We found that the enhancement of the photoelectrochemical properties was related to the homogeneity of the plasma-treated surfaces-arising from different spatial properties of the plasma between volume and coplanar DBDs. Furthermore, the results showed that plasma mineralization using coplanar DBD can effectively change the energy levels of the surface. This resulted in the enhancement of the work function and the photoelectrochemical properties of the mesoporous TiO2 photoanodes. This contribution shows that coplanar arrangement of electrodes in DBDs generates plasma of higher efficacy compared with standard volume DBD that is currently often used in industrial processes.

Numerical study of the influence of dielectric tube on propagation of atmospheric pressure plasma jet based on coplanar dielectric barrier discharge

A 2D fluid model was employed to simulate the influence of dielectric on the propagation of atmospheric pressure helium plasma jet based on coplanar dielectric barrier discharge (DBD). The spatio-temporal distributions of electron density, ionization rate, electrical field, spatial charge and the spatial structure were obtained for different dielectric tubes that limit the helium flow. The results show that the change of the relative permittivity of the dielectric tube where the plasma jet travels inside has no influence on the formation of DBD itself, but has great impact on the jet propagation. The velocity of the plasma jet changes drastically when the jet passes from a tube of higher permittivity to one of lower permittivity, resulting in an increase in jet length, ionization rate and electric field, as well as a change in the distribution of space charges and discharge states. The radius of the dielectric tube has a great influence on the ring-shaped or solid bullet structure. These results can well explain the behavior of the plasma jet from the dielectric tube into the ambient air and the hollow bullet in experiments.