Low-temperature Atmospheric Pressure Plasma Jet Research Articles

Potential formation on floating metal plate treated by low-temperature atmospheric pressure plasma jet

In the biomedical applications using low-temperature atmospheric pressure plasmas, charging on surface of the targets could play an important role. In this study, we have investigated potential formed on an electrically floating copper plate treated by a low-temperature atmospheric pressure helium plasma jet. The potential of the copper plate was measured by an electrostatic sensor in a non-contact manner. It was found that the potential on the copper plate could be controlled from 200 to −600 V by changing the distance between the nozzle of plasma device and the surface of copper plate. We discussed the charging mechanism such as collection of charged particles and several processes of electron emission including thermionic, field emission, secondary electron emission, and photoelectric processes.

Investigation of sterilization by a microwave-generated low-temperature atmospheric pressure plasma jet

An investigation of sterilization by a low-temperature microwave-generated atmospheric pressure plasma jet (MAPPJ) is presented. Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and yeast Saccharomyces species (Saccharomyces sp.) at 1.0 × 103 and 1.0 × 104 cfu/mL dilutions are investigated and fungi tested experimentally. The MAPPJ is generated by several watt continuous-wave microwaves and Ar gas, and direct treatment of the bacteria by a programmable planar XY motorized translation stage. After several minutes of plasma treatment, the number of bacterial colonies was sufficiently reduced and found to be nearly zero, and bare ozone and nitrogen dioxide were observed. This investigation shows that plasma sterilization would be a novel application for solid-state microwave power sources.

Study on the effect of low-temperature atmospheric pressure plasma jet on the morphofunctional properties of living tissues (in vivo)

The results of spectral-fluorescent and diffuse-optical studies of living tissues under the effect of low-temperature atmospheric pressure plasma jet in a mixture of air and argon are presented. Potential fluorophores are identified and coefficients of optical absorption and transport scattering of tissues are determined. It was revealed plasma jet irradiation of tissue leads to an increase in the intensity of fluorescence and the diffuse reflection coefficient, which is linked with a twofold increase in the transport scattering coefficient and a change in the concentration of endogenous chromophores --- a reducing water content, lipids and bilirubin to 20%, and an increasing levels of oxygen saturation to 10%. On the basis of the analysis, it is shown that the therapeutic effect of low-temperature plasma can be associated with increased antioxidant protection and the development of compensatory dehydration processes. Keywords: biological tissues, cold plasma, probing, spectroscopy, fluorescence, diffuse reflection, optical coefficients, light scattering, biochemistry, morphology.

Исследование морфофункциональных свойств биотканей ( in vivo) при воздействии низкотемпературной плазменной струи атмосферного давления

The results of spectral-fluorescent and diffuse-optical studies of living tissues under the effect of low-temperature atmospheric pressure plasma jet in a mixture of air and argon are presented. Potential fluorophores are identified and coefficients of optical absorption and transport scattering of tissues are determined. It was revealed plasma jet irradiation of tissue leads to an increase in the intensity of fluorescence and the diffuse reflection coefficient, which is linked with a twofold increase in the transport scattering coefficient and a change in the concentration of endogenous chromophores – a reducing water content, lipids and bilirubin to 20%, and an increasing levels of oxygen saturation to 10%. On the basis of the analysis, it is shown that the therapeutic effect of low-temperature plasma can be associated with increased antioxidant protection and the development of compensatory dehydration processes.

Interaction of low-temperature atmospheric pressure plasma jet mixed with argon and air with living tissues

The paper presents the results of spectral-fluorescence and diffuse-optical studies of biological tissues when exposed to a low-temperature atmospheric pressure plasma in a mixture of air with argon with an exposure of up to 10 minutes. Potential fluorophores were identified and the coefficients of optical absorption and transport scattering of biological tissues were determined. The analysis conducted allows to conclude that plasma probing leads to significant inhibition of cellular respiration and the development of coagulation effects in biological tissues.

Analysis of Hydroxyl Radical and Hydrogen Peroxide Generated in Helium-Based Atmospheric-Pressure Plasma Jet and in Different Solutions Treated by Plasma for Bioapplications

This study systematically analyzed reactive species generated with self-built helium-based low-temperature atmospheric-pressure plasma jet (He-APPJ); we measured the hydroxyl radical (·OH) and hydrogen peroxide (H2O2) above surfaces of plasma–treating solutions and in plasma-treated medium (PTM) of different solutions, including deionized water, phosphate buffered saline, and Dulbecco’s modified Eagle medium. The effects of adding O2 into He working gas on ·OH and H2O2 generation were discussed. The MCF7 cell responses to plasma treatment were also observed. The ·OH emission (309 nm) in He-APPJ and above surfaces of plasma–treating solutions were analyzed through optical emission spectroscopy, and concentrations of ·OH and H2O2 in different solutions were measured using terephthalic acid and Amplex Red, respectively. In our plasma system, it was observed that higher conductivity of solutions may cause stronger ·OH emission above solution. The ingredients of the solution may affect the concentrations of ·OH and H2O2. Addition of 0.1% O2 generates strongest ·OH emission above surfaces of plasma–treating solution with our He-APPJ, and thus, the highest H2O2 concentration in PTM. The MCF7 cell viability is influenced by the H2O2 concentration in PTM. The results of this study can facilitate further study of plasma effects on PTM and cell culture.

Application of persulfate in low-temperature atmospheric-pressure plasma jet for enhanced treatment of onychomycosis

Fungal infection of human nails, or onychomycosis, affects 10% of the world’s adult population, but current therapies have various drawbacks. In this work, we employed a self-made low-temperature plasma (LTP) device, namely, an atmospheric-pressure plasma jet (APPJ) device to treat the nails infected with Trichophyton rubrum (T. rubrum) with the aid of persulfate solution. We found that persulfate solution had a promoting effect on plasma treatment of onychomycosis. With addition of sodium persulfate, the APPJ therapy could cure onychomycosis after several times of treatment. As such, this work has demonstrated a novel and effective approach which makes good use of LTP technique in the treatment of onychomycosis.

Measurements of emission-propagation phenomena in low-energy atmospheric-pressure helium plasma

In a low-temperature atmospheric pressure plasma jet using helium gas, emission-propagation phenomena, such as streamers and striations were measured using a high-speed intensified charge-coupled device camera. A particular focus was placed on the study of the dependence of the phenomena on the distance between the nozzle of the plasma device and a target plate. When the distance decreased, a transition from the positive streamer to a spatially continuous emission resulted. A further distance reduction resulted in a new propagation mode in which the positive and negative streamers appeared alternately with different current waveforms over two cycles of applied voltage. This phenomenon may be related to residual charges of the preceding cycle when streamer propagation begins. Striation structures were observed in the tail of the positive streamer head and in the successive spatially continuous-emission region. These structures can be measured only within a shorter period than one voltage cycle.

Synergistic effects of plasma-activated medium and chemotherapeutic drugs in cancer treatment

Chemotherapy is an important treatment method for metastatic cancer, but the drug-uptake efficiency of cancer cells needs to be enhanced in order to diminish the side effects of chemotherapeutic drugs and improve survival. The use of a nonequilibrium low-temperature atmospheric-pressure plasma jet (APPJ) has been demonstrated to exert selective effects in cancer therapy and to be able to enhance the uptake of molecules by cells, which makes an APPJ a good candidate adjuvant in combination chemotherapy. This study estimated the effects of direct helium-based APPJ (He-APPJ) exposure (DE) and He-APPJ-activated RPMI medium (PAM) on cell viability and migration. Both of these treatments decreased cell viability and inhibited cell migration, but to different degrees in different cell types. The use of PAM as a culture medium resulted in the dialkylcarbocyanine (DiI) fluorescent dye entering the cells more efficiently. PAM was combined with the anticancer drug doxorubicin (Doxo) to treat human heptocellular carcinoma HepG2 cells and human adenocarcinomic alveolar basal epithelial A549 cells. The results showed that the synergistic effects of combined PAM and Doxo treatment resulted in stronger lethality in cancer cells than did PAM or Doxo treatment alone. To sum up, PAM has potential as an adjuvant in combination with other drugs to improve curative cancer therapies.

Tooth bleaching by using a helium-based low-temperature atmospheric pressure plasma jet with saline solution

In this study, tooth bleaching was performed by using a helium-based low temperature atmospheric-pressure plasma jet (He-APPJ) with saline solution to avoid ozone and hydrogen peroxide (H2O2) harm. In this study, tooth samples were treated through three approaches, namely a helium flow with saline, H2O2 gel, and He-APPJ with saline. The bleaching efficacy of the He-APPJ treatment was the highest among the three groups. Furthermore, scanning electron microscopy images showed that enamel treated with He-APPJ was much less damaged than that treated with H2O2 gel. In addition, ozone tests showed that APPJ produced little ozone (<0.35 ppm). In conclusion, He-APPJ with saline solution achieves higher bleaching efficacy and is less harmful than methods that use H2O2 gel.

Surface characterization of organosilicon films by low-temperature atmospheric-pressure plasma jet

A new plasma discharge jet was created to carry out the vacuum-free formation of organosilicon thin films at atmospheric pressure. The properties of the plasma-jet-deposited organosilicon film surfaces were evaluated for different plasma powers by contact-angle, scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS) analyses. The surface analysis indicates that the plasma power is the main factor affecting film growth by plasma chemical vapor deposition at atmospheric pressure. Analysis of the surface morphology by SEM and AFM indicates that smooth and uniform organosilicon thin films can be synthesized at a relatively low plasma power. Chemical detection by XPS is used to examine the mainly inorganic characteristics of the plasma-jet-deposited organosilicon films. The results of this investigation demonstrate the possibility of growing vacuum-free plasma-deposited films for large-area processing.

Electronic ground state OH(X) radical in a low-temperature atmospheric pressure plasma jet

The wide applicability of atmospheric pressure plasma jets in biomedicine stems from the presence of reactive nitrogen and oxygen species generated in these plasma jets. Knowing the absolute concentration of these reactive species is of utmost importance as it is critical, along with the particle flux obtained from the plasma feed gas flow rate to ensure that the correct dosage is applied during applications. In this study, we investigate and report the ground state OH(X) number density acquired using cavity ringdown spectroscopy, along the propagation axis (z-axis) of a cold atmospheric pressure helium plasma plume. The jet was generated by a repetitively pulsed mono-polar square wave of duration 1 μs running at a frequency of 9.9 kHz. The voltage supplied was 6.5 kV with the helium flow rate fixed at 3.6 standard liters per minute. The rotational and vibrational temperatures are simulated from the second positive system of nitrogen, N2(C3πu−B3πg), with the rotational temperature being spatially constant at 300 K along the propagation axis of the atmospheric pressure plasma jet while the vibrational temperature is 3620 K at the beginning of the plume and is observed to decrease downstream. The OH(A) emission intensity obtained via optical emission spectroscopy was observed to decrease downstream of the plasma jet. The OH(X) number density along the propagation axis was initially 2.2 × 1013 molecules cm−3 before increasing to a peak value of 2.4 × 1013 molecules cm−3, from which the number density was observed to decrease to 2.2 × 1013 molecules cm−3 downstream of the plasma jet. The total OH(A, X) in the plasma jet remained relatively constant along the propagation axis of the plasma jet before falling off at the tip of the jet. The increase in vibrational temperature downstream and the simultaneous measurements of both the excited state OH(A) and the ground state OH(X) reported in this study provide insights into the formation and consumption of this reactive oxygen species while also providing a reference for determining the radical number density dosage for future cold plasma irradiation studies.

Skin decontamination by low-temperature atmospheric pressure plasma jet and dielectric barrier discharge plasma

Over the past few years, plasma medicine has become an important field in medical science. Cold plasma has proven anti-inflammatory, antimicrobial and antineoplastic effects. To test the decontamination power of two cold plasma sources [low-temperature atmospheric pressure plasma jet (APPJ) and dielectric barrier discharge plasma (DBD)] in vivo on human fingertips. After 3, 15, 30, 60, 90, 120, 150, 180, 210 and 240 s of spot treatment with the APPJ and DBD, the log reduction factors (RFs) of physiological (PF) and artificially (AF) contaminated flora (Staphylococcus epidermidis and Micrococcus luteus) were calculated. The bacterial load was determined after counting. Tolerance (paresthesia, pain and heat) was measured using a numerical rating scale. Both plasma devices led to a significant reduction in PF and AF. The maximum log reduction factors for PF were 1.3 for the DBD at 210 s and 0.8 for the APPJ at 60 s. For AF, the maximum log reduction factors were 1.7 for the DBD at 90 s and 1.4 for the APPJ at 120 s. Treatment with both devices was well tolerated. Both the APPJ and DBD were highly effective in eradicating PF and AF from the fingertips of healthy volunteers. No plasma-resistant isolates were observed. Cold plasma appears to have potential for skin disinfection. For hand hygiene purposes, plasma exposure times would need to be reduced significantly by technical means.

Chaos in atmospheric-pressure plasma jets

We report detailed characterization of a low-temperature atmospheric-pressure plasma jet that exhibits regimes of periodic, quasi-periodic and chaotic behaviors. Power spectra, phase portraits, stroboscopic section and bifurcation diagram of the discharge current combine to comprehensively demonstrate the existence of chaos, and this evidence is strengthened with a nonlinear dynamics analysis using two control parameters that maps out periodic, period-multiplication, and chaotic regimes over a wide range of the input voltage and gas flow rate. In addition, optical emission signatures of excited plasma species are used as the second and independent observable to demonstrate the presence of chaos and period-doubling in both the concentrations and composition of plasma species, suggesting a similar array of periodic, quasi-periodic and chaotic regimes in plasma chemistry. The presence of quasi-periodic and chaotic regimes in structurally unbounded low-temperature atmospheric plasmas not only is important as a fundamental scientific topic but also has interesting implications for their numerous applications. Chaos may be undesirable for industrial applications where cycle-to-cycle reproducibility is important, yet for treatment of cell-containing materials including living tissues it may offer a novel route to combat some of the major challenges in medicine such as drug resistance. Chaos in low-temperature atmospheric plasmas and its effective control are likely to open up new vistas for medical technologies.

Hybrid Laser-Plasma Micro-Structuring of Fused Silica Based on Surface Reduction by a Low-Temperature Atmospheric Pressure Plasma

In this contribution, we report on a novel hybrid laser-plasma method for material processing applications. This method is based on the combination of both an ArF excimer laser (λ = 193 nm) and a low-temperature atmospheric pressure plasma jet source for the chemical reduction of glass surfaces. Here, a hydrogen-containing plasma gas was applied. Due to the layer of silicon suboxide that is generated in this vein, the absorption of the incoming machining laser beam is significantly increased after 15 minutes of plasma-treatment. Several machining experiments in terms of frontside ablation were performed on fused silica. Here, both pure and plasma-treated surfaces were ablated using single laser pulses with a pulse duration of 20 ns. By introducing the presented hybrid technique, the ablation threshold for micro-structuring was reduced significantly by a factor of 4.6 whereas the peak-to-valley height Rz of the machined area was decreased by a factor of 2.3. Further, back-side ablation using the presented method was considered. By a terminal tempering process, the initial transmission characteristics of fused silica can be reconstituted.

Laser Micro-Structuring of Fused Silica Subsequent to Plasma-Induced Silicon Suboxide Generation and Hydrogen Implantation

A low-temperature atmospheric pressure plasma jet was used for chemical reduction of fused silica. For this purpose, a hydrogen-containing plasma was applied. A silicon suboxide layer was generated and hydrogen was implanted into the bulk material. Changes in stoichiometry, concentration of hydrogen and optical transmission were determined. An ArF excimer laser was used for the ablation of untreated and plasma-treated fused silica. The ablation threshold was significantly decreased by a factor of 4.6 in case of plasma treated substrates. Furthermore, in multi-pulse experiments, the ablation rate remained constant at least up to a depth of 10.5 μm.

Plasma Medicine in Dermatology: Basic Antimicrobial Efficacy Testing as Prerequisite to Clinical Plasma Therapy

Plasma medicine has become an emerging field in medical sciences since cold plasma has demonstrated significant antibacterial properties in vitro and in vivo. However, systematic antimicrobial plasma testing against bacteria, fungi, and parasites is still lacking. Chronic wounds, fungal skin and nail infections, and colonization with multidrug-resistant pathogens like Staphylococcus aureus (MRSA) often pose significant therapeutic and economical problems and new therapeutic concepts are strongly warranted. The challenge of worldwide increasing resistance problems including different pathogens like methicillin-resistant MRSA, vancomycin-resistant enterococci, and gram-negative species producing betalactam hydrolysing enzymes (extended spectrum s-lactamases) constitute the need for alternative antimicrobial treatments. Cold plasma therapy with a completely different mode of action compared to conventional antimicrobials may offer an alternative to conventional external antibiotic and antiseptic therapies. In order to estimate the possible role as physical antiseptic, basic susceptibility data from plasma are needed. To provide such data, the plasma susceptibility of representative skin and wound pathogens against low-temperature atmospheric pressure plasma jet (APPJ device) and dielectric barrier discharge plasma treatment was tested in vitro on agar. The same plasma sources were used to test clinical fungal isolates in vitro and isolates of the parasite demodex folliculorum ex vivo. Plasma treatment proved to be highly effective in eradicating all treated strains and species including Escherichia coli, Pseudomonas aeruginosa, Klebsiella group (K. pneumoniae ssp. pneumoniae, K. oxytoca), Staphylococcus aureus, hemolysing Lancefield Streptococci (group A and B), Proteus group (P. mirabilis, P. vulgaris), Acinetobacter spp., Stenotrophomonas spp., Enterococcus faecalis, Candida albicans, and Staphylococcus epidermidis. Plasma irradiation of Trichophyton rubrum, Trichophyton interdigitale, Microsporon canis, and the yeast Candida albicans was able to kill >90% of the organisms during 30 s in vitro with no isolate exhibiting resistance. The APPJ-plasma killed Demodex folliculorum after exposure time of 2 s. Our data suggest plasma as a possible new option in the treatment of microbial, fungal, and parasitic dermal infections.

In Vitro Killing of Clinical Fungal Strains by Low-Temperature Atmospheric-Pressure Plasma Jet

Plasma medicine is an expanding focus and offers new aspects of therapy combining potent physical partial efficacies, like such as ultraviolet, infrared, and reactive species and particles, and nowadays, many successful treatments of different illnesses have been described. Fungal skin and nail infections pose significant therapeutic and economical problems. To test the plasma susceptibility of clinical strains of the most frequently encountered fungal species involved in dermatomycosis, clinical isolates of Trichophyton interdigitale, Trichophyton rubrum, Microsporum canis, and Candida albicans were irradiated by a cold atmospheric pressure plasma jet. Punctual plasma irradiation eradicated fungal growth of all species with the largest inactivation zones with most progress in the first 15 s of treatment, treating C. albicans and least progress in that of , the lowest being M. canis. No isolate exhibited resistance to plasma treatment. Plasma treatment also completely eradicated reproductive fungal elements of T. interdigitale in dandruff of patients with tinea pedis ex vivo and in the environment in contaminated shoes. Accordingly, cold plasma seems suited to antifungal in vivo treatment of fungal skin infections and decontamination of environmental infective material.

Synthesis of Organosilicon Film on Polycarbonate by Means of Low-Temperature Atmospheric-Pressure Plasma Jet

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Plasma-polymerized organosilicon films are deposited at room temperature by a novel double-pipe-type atmospheric-pressure plasma jet (APPJ), using hexamethyldisilazane (HMDSN) as precursor and argon (Ar) as carrier gas. The surface properties of the resulted plasma films are investigated as a function of radio-frequency plasma power and position from the plasma nozzle. The atmospheric-pressure plasma-polymerized films have been analyzed by static contact angle measurement, a Fourier transform infrared spectrometer, a UV–vis spectrometer, and atomic force microscopy. The ultrathin APPJ-polymerized films have been studied and correlated to chemical composition and surface morphology. UV–vis spectra have demonstrated the optical transparency of the APPJ polymerized films. </para>