Non-thermal Plasma Torch Research Articles

Effective degradation of organic water pollutants by atmospheric non-thermal plasma torch and analysis of degradation process

The paper reports the use of atmospheric non-thermal plasma torch as a catalyst for degradation of various organic pollutants dissolved in water. A flow of He mixed with air was used to produce the dielectric barrier discharge (DBD), at the tip of the torch, using pulsed electric excitation at 12 kV. The torch, operated at a power of 750 mW/mm2, was seen to completely degrade the aqueous solutions of the pollutants namely methylene blue (MB), methyl orange (MO) and rhodamine-B (RB), at around 10−4 M concentrations, the concentration of polluants is one order higher than of routinely used heterogeneous photocatalytic reactions, within 10 min of irradiation time at room temperature. UV Visible spectra of the organic dye molecules, monitored after different intervals of plasma-irradiation, ranging between 1 and 10 min, have been used as tools to quantify their sequential degradation. Further, instead of using He, only air was used to form plasma plume and used for degradation of organic dye which follow similar trend as that of He plasma. Further, Liquid Chromatography Mass Spectroscopy (LCMS) technique has been used to understand degradation pathway of methylene blue (MB) as a representative case. Total organic carbon (TOC) measurements indicates significant decrease in its content as a function of duration of plasma exposure onto methylene blue as a representative case. Toxicity studies were carried out onto Gram negative Escherichia coli. This indicated that methylene blue, without plasma treatment, shows growth inhibition, whereas with plasma treatment no inhibition was observed.

Abstract B18: Non-thermal plasma, tirapazamine, and gap junctions: A novel approach to melanoma therapy through ROS induction

Abstract Melanoma cells typically have high levels of superoxide anion which may increase their susceptibility to cell death by reactive oxygen species (ROS). We have used this information to establish a system whereby melanoma cells are saturated with ROS through treatment with non-thermal plasma (NTP). NTP is formed from a mixture of highly charged helium and atmospheric gases to emit a total of 45 molecular species, many of which are ROS. We have recently demonstrated that NTP causes selective apoptotic cell death of melanoma cells as compared to normal skin keratinocytes when plated in co-culture. Since tumors flourish under low oxygen (hypoxic) conditions, we tested the effects of NTP under hypoxia. In order to enhance the effects of NTP, we combined this therapy with the experimental anticancer drug, tirapazamine, which promotes cell toxicity through DNA damage only under hypoxic conditions. The question then remains as to how to increase the target area of melanoma therapy. Our previous studies have demonstrated that gap junctions act via the bystander effect to enable the passage of cell-death promoting signals by NTP. We utilized stably transfected 1205Lu metastatic melanoma cells that express three different levels of gap junctions: endogenous low levels, increased levels through expression of connexin 43, or an absence of gap junctions due to expression of a dominant negative mutant connexin 43. We have shown that the cells with the mutant connexin 43 showed increased invasive potential as well as enhanced expression of HIF1α. The combination therapy with NTP and tirapazamine under hypoxic conditions caused a synergistic effect which increased cell death in all cells, yet was most apparent in the 1205Lu cells overexpressing the functional gap junctions. In addition, the target area of the NTP torch was dramatically increased under these conditions. This suggests that the ROS generated by NTP and tirapazamine induced the bystander effect and promoted the spreading of cell death signals well beyond the area of the plasma treatment. These results are indicative a novel future approach to melanoma therapy through selective ROS induction and modification of gap junction phenotype. Citation Format: Shoshanna N. Zucker, Cory Higley, Zethan Koch, Haneesha Goli, Peter Casey, Akeem Francis, Kevin Burke, Jennifer Zirnheld. Non-thermal plasma, tirapazamine, and gap junctions: A novel approach to melanoma therapy through ROS induction. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Melanoma: From Biology to Therapy; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(14 Suppl):Abstract nr B18.

Characterization of a non-thermal plasma torch in streamer mode and its effect on polyvinyl chloride and silicone rubber surfaces

In this study, a non-thermal plasma torch in steamer mode was characterized to apply for surface modification in ambient air. The plasma source is a central rod-ring configuration based on DBD operation. Mixture of Ar/air gases was passed through the hollow Copper rod. A home-built high voltage generator at 18.8 kHz was employed to ignite the plasma. Electrical features of plasma torch were studied and different regions of plasma were examined using optical emission spectroscopy to explore the reactive species that result in efficient treatment. The surfaces of polyvinyl chloride (PVC) and silicone rubber (SIR) films were treated by the cold plasma torch. Contact angle measurement shows the improvement of surface hydrophilicity and wettability. Analysis revealed that the surface energy of the films increases indicating their activation after plasma treatment. This process is attributed to increasing the polar component of the surface energy. • The cold plasma torch used is Inexpensive, efficient and easy to use. • OES revealed the plasma reactive species resulted in the surfaces activation. • Plasma treatment improves PVC and SIR wettability and makes them more efficient.

Preferential induction of apoptotic cell death in melanoma cells as compared with normal keratinocytes using a non-thermal plasma torch

Selective induction of apoptosis in melanoma cells is optimal for therapeutic development. To achieve this goal, a non-thermal helium plasma torch was modified for use on cultured cells in a temperature-controlled environment. Melanoma cells were targeted with this torch (1) in parallel cultures with keratinocytes, (2) in co-culture with keratinocytes and (3) in a soft agar matrix. Melanoma cells displayed high sensitivity to reactive oxygen species generated by the torch and showed a 6-fold increase in cell death compared with keratinocytes. The extent of cell death was compared between melanoma cells and normal human keratinocytes in both short-term (5 min) co-culture experiments and longer assessments of apoptotic cell death (18–24 h). Following a 10 sec plasma exposure there was a 4.9-fold increase in the cell death of melanoma vs. keratinocytes as measured after 24 h at the target site of the plasma beam. When the treatment time was increased to 30 sec, a 98% cell death was reported for melanoma cells, which was 6-fold greater than the extent of cell death in keratinocytes. Our observations further indicate that this preferential cell death is largely due to apoptosis.. In addition, we report that this non-thermal plasma torch kills melanoma cells growing in soft agar, suggesting that the plasma torch is capable of inducing melanoma cell death in 3D settings. We demonstrate that the presence of gap junctions may increase the area of cell death, likely due to the “bystander effect” of passing apoptotic signals between cells. Our findings provide a basis for further development of this non-invasive plasma torch as a potential treatment for melanoma.

Nonthermal Plasma Torch Surface Attachment in Fluidic Environments

The plasma jet of a nonthermal plasma torch was studied under various flow rates as it interacted with cell culture media. As the flow rate of the plasma working gas increases, the surface area of the attachment changes considerably. Effects in appearance range from a fine “jet” to a broad “skirt” that flutters in a disorganized pattern.

Exhaust Gas Fuel Reforming of Diesel Fuel by Nonthermal Arc Discharge for NOx Trap Regeneration Application

The present study is dedicated to the reforming of diesel fuel with diesel engine exhaust gas (i.e., air, CO2, and H2O mixture) using a nonthermal plasma torch for a NOx trap regeneration application. The plasma technology developed is based on a high voltage/low current nonthermal plasma torch. In the first part of the paper, experimental results on synthesis gas production from exhaust gas fuel reforming of diesel fuel are reported. In the second part of the paper, these experimental results are compared with a 1D multistage model using n-heptane as a surrogate molecule for diesel fuel. Two compositions of synthetic diesel engine exhaust gas, corresponding to high and low engine loads, have been studied. It has been demonstrated that the oxygen from CO2 and H2O hardly ever intervenes in the reforming reactions. In the most favorable condition corresponding to a higher O2 rate, a production of 7 × 10−3 mol·s−1 of syngas has been reached, corresponding to an energy efficiency and a conversion rate of 40% ...

Nonthermal Plasma Needle: Development and Targeting of Melanoma Cells

A nonthermal plasma torch has been developed to study the targeted killing of melanoma cells. In this paper, 1205Lu melanoma cells and keratinocytes were exposed to the plasma. These cells were transfected with green fluorescent protein in order to establish a system for coculture with primary keratinocytes. Results show that a 10 s treatment with plasma causes a morphological change in the melanoma cells, as observed after 18 h. However, after only 15 min following plasma treatment, a significant killing of melanoma cells was observed, with a much reduced killing of keratinocytes. Nonthermal plasma may serve as an effective tool for future therapeutic cancer treatment.

Numerical investigation on thermofluid fields induced by pen-like atmospheric non-thermal plasma torch with array type: A preliminary study

The pen-like plasma torch device, which was developed in 2002, has very simple structure and has been successfully applied for the surface treatment to improve hydrophilic properties of plastic film and polyethylene. However, due to the effective treating area of a single pen-like atmospheric plasma torch is still very limited, the current status of the device is still far from the practical applications. In view of this, the development of the new design of the “pen-like atmospheric plasma torch array”, which is composed of multiple pen-like atmospheric plasma torches, is undergoing. It is expected the array design of the plasma-torch system could increase the effective treating area and satisfy the need of practical applications. The present paper carried out the numerical simulations of the thermofluid fields induced by the devices with dual and four pen-like plasma torches. The major interest is to exploit the different flow features of single-, dual- and four-plasma torch system. The results revealed in the present study provide fundamental understanding of the thermofluid fields induced by the multiple pen-like plasma torches, which are worthwhile for the design work of the array-type devices.

Numerical and experimental investigation on the thermofluid fields induced by a pen-like atmospheric nonthermal plasma torch

The present paper carried out the numerical simulation and experimental study of the thermofluid fields induced by a pen-like atmospheric nonthermal plasma torch, which is a very simple device to produce atmospheric plasma and has been successfully applied for surface treatment to improve the hydrophilic properties of plastic film and polyethylene. The device consists of a small cylindrical stainless steel pipe with 6.5 mm diameter and 170 mm length inserted into a ceramic tube as the inner electrode. A ring outer electrode made of stainless steel is fixed at near the edge of the ceramic. The 13.56 MHz RF power was applied between the two electrodes to produce a surface discharge. The power into the torch is 60 W. The driving gas is argon and the flow rate varies in the range of 3–12 L min −1. Fundamental research results describing the major features of the flow fields induced by the plasma torch are provided in the present study. The stress is laid on the investigation of the influence of gas flow rate, which is one of important operation conditions, on the flow fields excited by the plasma torch. The principal results show that as the power input is fixed the increase of the gas flow rate will reduce the plasma temperature. The plasma penetration length stretching toward the atmospheric surroundings is also found to be closely related with the gas flow rate. Experimental confirmation by measuring the rotational temperature using optical spectroscopic method has been carried out, and a reasonable agreement between calculation and experiment has been obtained. These results provide fundamental understanding of the thermofluid fields induced by a pen-like atmospheric plasma torch, and also build up a basic predictive capability by numerical simulations to perform the further detailed investigation for practical applications in future.