Atmospheric pressure air plasma discharges generate potential antimicrobial agents, such as nitrogen oxides and ozone. Generation of nitrogen oxides was studied in a DC-driven self-pulsing (1–10 kHz) transient spark (TS) discharge. The precursors of NOx production and the TS characteristics were studied by nanosecond time-resolved optical diagnostics: a photomultiplier module and a spectrometer coupled with fast intensified camera. Thanks to the short (~10–100 ns) high current (>1 A) spark current pulses, highly reactive non-equilibrium plasma is generated. Ozone was not detectable in the TS, probably due to higher gas temperature after the short spark current pulses, but the NOx production rate of ~7 × 1016 molecules/J was achieved. The NO2/NO ratio decreased with increasing TS repetition frequency, which is related to the complex frequency-dependent discharge properties and thus changing NO2/NO generating mechanisms. Further optimization of NO2 and NO production to improve the biomedical and antimicrobial effects is possible by modifying the electric circuit generating the TS discharge.

Generation of Antimicrobial NO x by Atmospheric Air Transient Spark Discharge

Medical-grade polyvinyl chloride was coated by polysaccharides through a novel physicochemical approach. An initial surface activation was performed foremost via diffuse coplanar surface barrier discharge plasma in air at ambient temperature and pressure. Then, radical graft copolymerization of acrylic acid through grafting-from pathway was directed to render a well-defined brush of high density, and finally a chitosan monolayer and chitosan/pectin alternating multilayer were bound onto the functionalized surfaces. Surface characteristics were systematically investigated using several probe techniques. In vitro bacterial adhesion and biofilm formation assays indicated that a single chitosan layer was incapable of hindering the adhesion of a Staphylococcus aureus bacterial strain, while up to 30% reduction was achieved by the chitosan/pectin layered assembly. On the other hand, chitosan and chitosan/pectin multilayer could retard Escherichia coli adhesion by 50% and 20%, respectively. Furthermore, plasma treated and graft copolymerized samples were also found effective to diminish the degree of adherence of Escherichia coli.

https://www.mdpi.com/1420-3049/15/2/1007/pdf

Polysaccharides coatings on medical-grade PVC: a probe into surface characteristics and the extent of bacterial adhesion.

This paper presents our measurements of the electron density in a streamer-to-spark transition discharge, which is named transient spark (TS), in atmospheric pressure air. Despite the dc applied voltage, TS has a pulsed character with short (~10–100 ns) high current (>1 A) pulses, with a repetition frequency on the order of kHz. The electron density ne ~ 1017 cm−3 at maximum is reached in TS with repetition frequencies below ~3 kHz, using relatively low power delivered to the plasma (0.2–3 W).The temporal evolution of ne was estimated from the resistance of the plasma discharge, which was obtained by a detailed analysis of the electric circuit representing the TS and the discharge diameter measurements using a fast intensified charge-coupled device (iCCD) camera. This estimate was compared with ne calculated from the measured Stark broadening of several atomic lines: Hα, N at 746 nm, and O triplet at 777 nm. Good agreement was obtained, although the method based on the plasma resistance is sensitive to an accurate determination of the discharge diameter. We have found that this method is also limited for strongly ionized plasmas. On the other hand, a lower ne detection limit can be obtained by this method than from the Stark broadening of atomic lines.

https://iopscience.iop.org/article/10.1088/0963-0252/23/6/065016/pdf

Measurement of the electron density in Transient Spark discharge

We present results on the development of hydrophobic coatings on polymers in an atmospheric pressure dielectric barrier discharge (DBD). The effects of X + N2 DBD are studied, where X refers to chlorine- and/or fluorine- containing precursors, aiming at surface modification with chemically bound halogen-bearing entities. The discharge parameters and the treatment conditions were optimized, both in terms of diminution of the oxygen level in the reactor and efficient creation of X + N2 environments. Surface analysis and characterization were performed using x-ray photoelectron spectroscopy, contact angle measurement and scanning electron microscopy. The deposition of stable hydrophobic coatings, with a complex structure due to polymerization and cross-linking, with contributions from both halogen species, fluorine and chlorine, is demonstrated.

https://iopscience.iop.org/article/10.1088/0022-3727/40/7/015/pdf

Hydrophobic coatings on selected polymers in an atmospheric pressure dielectric barrier discharge

Polyethylene (PE) is one of the most widely used polymers in many industrial applications. Biomedical uses seem to be attractive, with increasing interest. However, PE it prone to infections and its additional surface treatment is indispensable. An increase in resistance to infections can be achieved by treating PE surfaces with substances containing antibacterial groups such as triclosan (5-Chloro-2-(2,4-dichlorophenoxy)phenol) and chlorhexidine (1,1'-Hexamethylenebis[5-(4-chlorophenyl)biguanide]). This work has examined the impact of selected antibacterial substances immobilized on low-density polyethylene (LDPE) via polyacrylic acid (PAA) grafted on LDPE by low-temperature barrier discharge plasma. This LDPE surface treatment led to inhibition of Escherichia coli and Staphylococcus aureus adhesion; the first causes intestinal disease, peritonitis, mastitis, pneumonia, septicemia, the latter is the reason for wound and urinary tract infections.

/pdf/anti-bacterial-treatment-of-polyethylene-by-cold-plasma-for-gj2ifuh923.pdf

Anti-bacterial treatment of polyethylene by cold plasma for medical purposes.

Thin layers of atmospheric-pressure non-equilibrium plasma can be generated by pulse surface corona discharges and surface barrier discharges developing on the treated surfaces or brought into a close contact with the treated surfaces. Plasma sources based on these discharge types have the potential of meeting the basic on-line production requirements in the industry and can be useful for a wide range of surface treatments and deposition processes including continuous treatment of textiles. Comparing with atmospheric pressure glow discharge sources, the potential advantages of these plasma sources include their simplicity, robustness, and capability to process in a wide range of working gases. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Generation of Thin Surface Plasma Layers for Atmospheric‐Pressure Surface Treatments

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Generation of Thin Surface Plasma Layers for Atmospheric‐Pressure Surface Treatments