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The transportation of drugs through model tissues that are being treated by an argon plasma jet was investigated in this paper. Gelatin gel films were used to construct the model tissues and lidocaine was used as a representative drug. The argon plasma jet enhanced the penetration of lidocaine and the enhancement rate increased with the discharge voltage and the frequency. When the discharge power of the plasma jet was low, it was deduced that the enhancement effect was mainly attributed to the electric field of the plasma jet. The enhancement effect was holistic and was hindered by the macromolecules of gelatin in the model tissues. When the discharge power of the plasma jet increased beyond a threshold level, the surface streamers of the plasma jet produced a deformation effect in the model tissue, thereby resulting in a star-shaped pattern on the surface of the model tissue. In that case, the penetration enhancement of lidocaine was dominated by the deformation effect; however, it was mainly confined to the surface layer. For comparison, a helium plasma jet was also used to enhance the penetration of lidocaine. When the discharge power was low, the enhancement effect of the helium plasma jet was higher than that of the argon plasma jet because the He gas flow and the electric field of He plasma jet enhanced the penetration of lidocaine jointly; however, the enhancement effect of the Ar plasma jet was only attributed to the electric field. When the discharge power increased beyond a threshold level, the enhancement effects of the two plasma jets were almost the same. [ABSTRACT FROM AUTHOR]

Argon is a widely used working gas of plasmas, which is much cheaper than helium but on the other hand much more difficult to generate diffuse discharge at atmospheric pressure. In order to meet the application requirements, plenty of researches have been reported to facilitate the diffuse discharge happening for argon plasmas, and in this paper an approach of using ethanol gas (EtOH) impurity is investigated. The discharge characteristics of Ar + EtOH plasma jet are studied as a function of the applied voltage and the concentration of EtOH, from which the concentration of EtOH between ∼200 and ∼3300 parts per million (ppm) is determined necessary for the generation of diffuse discharge. Compared with the helium plasma jet in literature, it is deduced that the diffuse discharge is probably caused by the Penning ionization happening between the metastable argon and EtOH. The discharge products of Ar + EtOH (672 ppm) plasma jet are measured and the corresponding chemistry pathways are analyzed. About 20% of EtOH is decomposed via complex chemical reactions to form more than a dozen of neutral species, such as CH3CHO, CH3COOH, CO, H2O, and CnH2n+2 (n ≥ 3), and various kinds of ionic species, including C+, CH+, ArH+, CH3CH2O−, etc. [ABSTRACT FROM AUTHOR]

Cold atmospheric-pressure plasmas in Ar + H2O gas mixtures are a promising alternative to He + H2O plasmas as both can produce reactive oxygen species of relevance for many applications and argon is cheaper than helium. Although He + H2O plasmas have been the subject of multiple experimental and computational studies, Ar + H2O plasmas have received less attention. In this work we investigate the composition and chemical pathways in Ar + H2O plasmas by means of a global model that incorporates 57 species and 1228 chemical reactions. Water vapor concentrations from 1 ppm to saturation (32 000 ppm) are considered in the study and abrupt transitions in power dissipation channels, species densities and chemical pathways are found when the water concentration increases from 100 to 1000 ppm. In this region the plasma transitions from an electropositive discharge in which most power is coupled to electrons into an electronegative one in which most power is coupled to ions. While increasing electronegativity is also observed in He + H2O plasmas, in Ar + H2O plasmas the transition is more abrupt because Penning processes do not contribute to gas ionization and the changes in the electron energy distribution function and mean electron energy caused by the increasing water concentration result in electron-neutral excitation and ionization rates changing by many orders of magnitude in a relatively small range of water concentrations. Insights into the main chemical species and pathways governing the production and loss of electrons, O, OH, OH(A) and H2O2 are provided as part of the study. [ABSTRACT FROM AUTHOR]