The subject of this paper is the recently developed 2.45 GHz microwave micro torch, which produces a surface wave discharge operating at low power of 25 W. Microwave plasma is generated using surfatron resonator in pure argon and argon with admixtures (up to 1.7%) of nitrogen and oxygen at the gas flow rate of 3 Slm. Two different configurations are used—a standard one and one with an additional metallic plate at the surfatron resonator end limiting the surface wave propagation along the plasma. Plasma parameters like temperatures (rotational, vibrational, electron) along the plasma torch axis as well as distribution of selected active particles are determined. The numeric simulation of the discharge and its properties are included, too. Finally, surface temperature of the fresh pork skin affected by the active particles flow is determined using thermo camera images. The obtained results show applicability of this system for the surface treatment of biological objects and possibility to modify the torch conditions by molecular gases additions.

Cold atmospheric pressure plasma (CAP) has attracted increased interest in recent years for possible biomedical, environmental and agricultural applications. A wide range of cold plasma treatment effects is observed in agricultural applications, like effects on the seed germination and seedling growth, but more systematic investigations are needed. The aim of this study was to identify the most appropriate combinations of the plasma source and duration of treatment positively affecting seed germination. In addition, the effect of cold plasma on the seedling growth and osmotic stress tolerance was studied. The seeds of three Bulgarian durum wheat cultivars were treated with cold plasma in twelve variants. The results obtained were processed statistically via two-way ANOVA. The treatment of seeds with a plasma torch for 20 s and the treatment with underwater diaphragm discharge for 5 min when the seeds were placed in both cameras in two different positions (relative to the electrodes between which the plasma is supplied, “+” and “−”) have the greatest positive effect on the all traits related to germination. The analysis of variance reveals that the variation in germination energy, shoot length and root length after the cold plasma treatment of seeds is mainly due to the interaction between the genotype and treatment variant and to a small degree due to the genotype. The treatment of seeds with cold plasma improves the osmoregulation ability of cells and therefore increases the drought resistance of genotypes.

The axial distributions of the electrons and ${\text{3p}}^5\text{4s}$ and ${\text{3p}}^5\text{4p}$ excited atoms in argon plasma columns sustained by traveling electromagnetic waves have been studied both experimentally and theoretically in the gas pressure range of 0.2–2.8 Torr. Various diagnostic methods (surface-wave interferometry, emission and absorption spectroscopy) have been used in data gathering. The theoretical model includes a self-consistent solution to the electron Boltzmann equation, electron energy balance equation, a set of balance equations for excited atoms and charged particles, the gas thermal balance equation, the wave dispersion relation, and the wave energy balance equation. The agreement between experimental data and theoretical results is very good.

The transformation of our linear “take-make-waste” system to a cyclic flow of materials and energy is a priority task for society, but the circular use of waste streams from one industry/sector as a material input for another must be completely safe. The need for new advanced technologies and methods ensuring both microbiological safety and the removal of potential chemical residues in used materials and products is urgent. Non-thermal atmospheric plasma (cold atmospheric plasma—CAP) has recently attracted great research interest as an alternative for operative solutions of problems related to safety and quality control. CAP is a powerful tool for the inactivation of different hazardous microorganisms and viruses, and the effective decontamination of surfaces and liquids has been demonstrated. Additionally, the plasma’s active components are strong oxidizers and their synergetic effect can lead to the degradation of toxic chemical compounds such as phenols and azo-dyes.

Demand for food quality and extended freshness without the use of harmful chemicals has become a major topic over the last decade. New technologies are using UV light, strong electric field, ozone and other reactive agents to decontaminate food surfaces. The low-power non-equilibrium (cold) atmospheric pressure operating plasmas effectively combines all the qualities mentioned above and thus, due to their synergetic influence, promising results in fruit surface decontamination can be obtained. The present paper focuses on the applicability of the recently developed microwave surface wave sustained plasma torch for the treatment of selected small fruit. Optical emission spectroscopy is used for the determination of plasma active particles (radicals, UV light) and plasma parameters during the fruit treatment. The infrared camera images confirm low and fully applicable heating of the treated surface that ensures no fruit quality changes. The detailed study shows that the efficiency of the microbial decontamination of selected fruits naturally contaminated by microorganisms is strongly dependent on the fruit surface shape. The decontamination of the rough strawberry surface seems inefficient using the current configuration, but for smooth berries promising results were obtained. Finally, antioxidant activity measurements demonstrate no changes due to plasma treatment. The results confirm that the MW surface wave sustained discharge is applicable to fruit surface decontamination.

Cold atmospheric plasma (CAP) applications in various fields, such as biology, medicine and agriculture, have significantly grown during recent years. Many new types of plasma sources operating at atmospheric pressure in open air were developed. In order to use such plasmas for the treatment of biological systems, plasma properties should fulfil strong requirements. One of the most important is the prevention from heating damage. That is why in many cases, the post-discharge region is used for treatment, but the short living particles in the active discharge zone and reactions with them are missed in that case. We use the active region of surface-wave-sustained argon plasma for biological systems treatment. The previous investigations showed good bactericidal, virucidal, seeds germination and decontamination effects at a short treatment time, but the discharge conditions for bio-medical applications need specific adjustment. A detailed theoretical and experimental investigation of the plasma characteristics and their possible optimization in order to meet the requirements for bio-medical applications are presented in this paper. The length of the plasma torch, the temperature at the treatment sample position and the microwave radiation there are estimated and optimized by the appropriate choice of discharge tube size, argon flow rate and microwave power.