2020, Baeva, Margarita, Loffhagen, Detlef, Becker, Markus M., Siewert, Erwan, Uhrlandt, Dirk

This paper describes the behaviour of the plasma parameters of microarcs generated between a cooled copper anode and a ceriated tungsten cathode by means of a one-dimensional unified non-equilibrium model for gap lengths between 15 and 200 μm and current densities from 2 × 105 up to 106 A/m2. The results obtained show that the decrease of the gap length to a few tens of micrometres for a given current density results in a progressive shrinking of the quasi-neutral bulk in the microplasma and its complete disappearance. The decrease of the gap length further leads to an increase of the discharge voltage and the electron temperature and to slightly less heating of the gas. © 2020 The Authors. Contributions to Plasma Physics Published by Wiley-VCH Verlag GmbH & Co. KGaA

2021, Sremački, Ivana, Bruno, Giuliana, Jablonowski, Helena, Leys, Christophe, Nikiforov, Anton, Wende, Kristian

A radio-frequency driven plasma jet in annular geometry coupled with an aerosol injection into the effluent is proposed for the controllable reactive oxygen species (ROS)/reactive nitrogen species (RNS) production and delivery on biological targets in the context of plasma medicine, e.g. wound care. The role of the aqueous aerosol in modulating the reactive species production is investigated by combining physical and chemical analytics. Optical emission spectroscopy, electron paramagnetic resonance spectroscopy, and a biochemical model based on cysteine as a tracer molecule have been applied, revealing that aerosol injection shifts the production of ROS from atomic and singlet oxygen toward hydroxyl radicals, which are generated in the droplets. Species generation occurred mainly at the droplets boundary layer during their transport through the effluent, leading to a limited cysteine turnover upon introduction into the aerosol solution. The subsequent delivery of unmodified cysteine molecules at a target suggested the application of the plasma source for the topical delivery of drugs, expanding the potential applicability and effectiveness. The presence of RNS was negligible regardless of aerosol injection and only traces of the downstream products nitrate and nitrate were detected. In summary, the aerosol injection into the effluent opens new avenues to control UV radiation and reactive species output for the biomedical applications of non-thermal plasma sources, reaching out toward the regulation, safety, and efficacy of targeted applications.