Dielectric Barrier Discharge Setup Research Articles

Boost of cosmetic active ingredient penetration triggered and controlled by the delivery of kHz plasma jet on human skin explants

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

Long filamentary discharge produced in helium spiral vortex

We report the generation of long plasma filament confined in a helium spiral vortex at atmospheric pressure. The discharge is produced by a dielectric barrier discharge setup and confined in the center of a spiral vortex. The length of the discharge can be several centimeters with flow rate less than 1 SLM. We find that the long filamentary discharge is the trajectory of fast-traveling plasma bursts and plasma plumes, where the plasma bursts are similar to the plasma jet produced at atmospheric pressure. The speeds of the downstream and upstream plasma bursts are about 46 000 and 95 000 m/s, respectively, which are affected by the spirally upward helium gas flow. Based on the novel design of vortex-confined discharge, we show that a plasma filament with a length of 10 cm can be produced.

Design and development of dielectric barrier discharge setup to form plasma-activated water and optimization of process parameters

Design and development of dielectric barrier discharge setup to form plasma-activated water and optimization of process parameters

Silanization of Plasma-Activated Hexamethyldisiloxane-Based Plasma Polymers for Substrate-Independent Deposition of Coatings with Controlled Surface Chemistry.

Plasma polymerization has emerged as an appealing technique for surface modification because of its advantages over a variety of conventional techniques, including ease-of-use and the possibility to modify nearly any substrate. One of the main challenges of plasma polymer-based surface modification, however, is having control over the coating chemistry, as plasma deposition generates a diversity of chemical structures. Therefore, this study presents an alternative plasma-based method for the fabrication of coatings that contain selective functionalities. In a first step, hexamethyldisiloxane (HMDSO) plasma polymerization is performed in a medium-pressure dielectric barrier discharge (DBD) to deposit polydimethylsiloxane (PDMS)-like coatings. In a second step, this coating is exposed to an air plasma in a similar DBD setup to introduce silanol groups on the surface. These groups are used in a third and final step as anchoring points for grafting of (3-aminopropyl)triethoxysilane (APTES) and (3-bromopropyl)trichlorosilane (BrPTCS) to selectively introduce amino or bromo groups, respectively. X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) measurements indicated that the first two steps were successful. Moreover, the coating could be synthesized on three different surfaces, namely, glass, ultrahigh-molecular-weight polyethylene, and polytetrafluoroethylene, indicating the wide applicability of the developed procedure. Afterward, XPS also proved that the APTES and BrPTCS grafting resulted in the formation of a coating containing primary amines and alkyl bromides, respectively, in combination with an organosilicon matrix containing silanol groups as remaining reactive groups, proving the successful synthesis of selective functional plasma-based coatings. The intermediate air-plasma-activation step was demonstrated to be necessary for successful and stable grafting of the final layer. In conclusion, this study established a general procedure for the development of coatings with selective functionality that can be applied on a wide variety of substrates for, e.g., biosensor applications, biomolecule, or polymer immobilization or for the synthesis of antibacterial coatings.

Treatment of Flax Fabric with AP-DBD in Parallel Plane Configuration

For the use of natural fibers in composite materials it is often necessary to improve the compatibility between fiber (sizing) and polymer matrix systems, e.g., by increasing the number of functional groups on the fiber surfaces. In this work, a dielectric barrier discharge (DBD) source in plane configuration is used to treat flax fabrics in ambient air. It is examined whether it is possible to increase the functionality on both fabric sides, which is achieved by simple changes in the DBD setup. After evaluating the treatment homogeneity of the filamentary plasma, an explanation for the treatment mechanism on the fiber surfaces is developed. It is shown that waxy substances, which naturally occur on natural fibers, play an important role in the wettability of the fabric.

Parameters Identification and Gas Behavior Characterization of DBD Systems

This paper proposes an efficient modeling and an identification method for dielectric barrier discharge (DBD) systems, based on input–output (current–voltage) experimental measurements. The DBD is modeled using an equivalent electric circuit associated with a differential equation that describes the dynamics of its conductance. This equation assumes a homogeneous behavior of the gas. This paper introduces a series of polynomial terms of the current of the gas into the conductance equation. These terms, after identification, are a very useful tool to analyze the physical mechanisms that take place in the gas. The identification process also returns the numerical values of other DBD parameters, such as associated capacitances and the breakdown voltage. In addition, an asymmetric model for the gas, which considers the direction of the current, is proposed to consider the possible geometrical dissimilarity between the two electrodes of the DBD setup. Experimental measurements taken on two different DBD applications are used for validating the proposed approach.

Fabrication of Al doped ZnO films using atmospheric pressure cold plasma

Under atmospheric pressure, homogeneous non-equilibrium cold plasma was generated stably by high voltage pulsed power (1kV, 20kHz, 38W) excitation of a mixture of He and O2 gases produced by a dielectric barrier discharge setup. By feeding Bis (2 methoxy‐6-methyl‐3, 5-heptanedione) Zn (Zn-MOPD, C18H3O6Zn) and Tris (2-methoxy‐6‐methy l‐3, 5-heptanedione) Al (Al-MOPD, C27H45O9Al) into this plasma with He carrier gas, transparent flat Al-doped ZnO (ZnO:Al) films about 120–240nm thick were prepared on glass substrates directly under the slit made into the cathode. Deposition rates of the films were about 20–40nm/min. The concentration of Al was measured by inductively coupled plasma atomic emission spectroscopy. The composition ratio of Al to Zn was 7.8mol% when the carrier He gas flow rate of Al-MOPD was 30cm3. The average transmittance of all films was more than 85% in the wavelength range from 400 to 800nm. When the composition ratio of Al/Zn was between 1.1 and 7.8mol%, the optical band gap of the film increased from 3.28 to 3.40eV. The resistivity of ZnO:Al film was 2.96Ωcm at 1.3mol% of Al/Zn. In addition, the microstructure of the films was studied by X-ray diffraction measurement and field emission scanning electron microscope observation. It was revealed that doped Al is substituted onto the Zn site of the ZnO crystalline structure in ZnO:Al films.

Atmospheric pressure plasma jets beyond ground electrode as charge overflow in a dielectric barrier discharge setup

With a proper combination of applied voltage and the width of ground electrode, atmospheric pressure plasma jets extending beyond the ground electrode, whether it sits on the downstream or the upstream side, can be equally obtained with a dielectric barrier discharge setup, which can be ascribed to the overflow of deposited charges [J. Appl. Phys. 106, 013308 (2009)]. Here, we show that, by using narrower ground electrodes, such an overflow jet can be successfully launched at a much reduced voltage (down to below 10 kV). Moreover, by using transparent and triadic ground electrodes, development of charge overflow beneath the ground electrode was temporally and spatially resolved. Temporal evolution of discharge currents measured on the severed ground electrode helps establish the propagation dynamics of discharges along the dielectric surface beneath ground electrode, and also reinforces the conception that the streamer’s head is in connection to the active electrode via a conducting channel. A small propagation velocity of 3.3×103 m/s was measured for the “overflow” jet inside the dielectric tube. The availability of such overflow jets is enormously advantageous concerning their application to living bodies, to which the high voltage at active electrode is lethally dangerous.

Surface treatment of a polypropylene film with a nitrogen DBD at medium pressure

Surface treatment of polymer films is usually necessary to improve surface wetting and adhesion characteristics. Traditional liquid chemical processes have several disadvantages in contrast to dry finishing processes, like plasma technology. Dielectric barrier discharges at atmospheric pressure are extensively studied for surface treatment, however, almost no research has been done on surface treatment with a dielectric barrier discharge at medium pressure. Therefore, in this paper, a polypropylene (PP) film is plasma-treated with a dielectric barrier discharge (DBD) in nitrogen at medium pressure (5.0 kPa). The surface properties of the plasma-treated samples are examined using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results show that the surface wettability is significantly enhanced after plasma treatment. The incorporation of nitrogen on the surface is significant (10 at%), demonstrating the ability of the used DBD set-up to generate nitrogen-containing functional groups on the PP surface. Nevertheless, a considerable amount of oxygen (10 at%) is incorporated onto the PP surface underlining the extreme reactivity of oxygen active species and the difficulty in overcoming the air contamination problem. Moreover, AFM analysis reveals that the nitrogen plasma creates large changes in the surface morphology of the PP film due to the selective etching of the amorphous regions of the polymer film.

Spatial and temporal evolution of a dielectric barrier discharge

Experimental study of spatial and temporal evolution of a dielectric barrier discharge (DBD) during a single current pulse is reported. The discharge light emission has been imaged using a high-speed intensified charge-coupled device camera. The time-resolved light emission data have been combined with the discharge current and applied voltage waveforms measurements. The discharge behavior has been found to be dependent on the external circuit impedance and bandwidth. Being nonstationary in principle, the DBD can exhibit both time evolution and development over the electrode area. For a typical DBD setup with flat parallel electrodes, the discharge breakdown occurs in the electrode’s central part; then, the plasma column expands to the electrode’s peripheries and gradually fills up the entire electrode area. The powering system should be able to provide enough current value during the discharge glow to achieve a simultaneous breakdown over the whole electrode area. In this case, the discharge appears over the entire electrode’s area and the plasma column exhibits temporal evolution only. The measured discharge characteristics for different power supply architectures had shown the evidence of a “normal current density” effect in DBD glow.

Pattern formation in the dielectric barrier discharge in argon at atmospheric pressure

The hexagon and square gridding patterns were observed in Ar（0.5％Air） at atmospheric pressure by using a dielectric barrier discharge set-up with double water electrodes. The temporal behaviour of an individual filament in square gridding was measured. The experimental results show that the time interval between two adjacent discharges are changed between long and short alternately. The influence of the charges deposited on dielectric surface on the self-organized filament pattern has been discussed.