The spatial density distribution of H₂O₂ in the effluent of the COST-Jet and the kINPen-sci operated with a humidified helium feed gas

Abstract

Cold atmospheric plasma jets operated with a helium feed gas containing small admixtures of water vapour are excellent sources of H2O2 for direct biomedical applications. However, H2O2 is typically distributed non-uniformly throughout the effluent region, meaning the dosage received by a patient or substrate is dependent on their positioning relative to the plasma source. This study presents the spatial distribution of absolute H2O2 number densities in the effluent of two popular plasma jets, the COST-Jet and the kINPen-sci plasma jet, when operated with a humidified helium feed gas. The measurements were performed using continuous wave cavity ring-down spectroscopy with a tunable, mid-infrared laser. The H2O2 number density measured close to the jet nozzle is 2.3x10^14 cm^-3 for the kINPen-sci plasma jet and 1.4x10^14 cm^-3 for the COST-Jet. The average number density of H2O2 in the effluent of the kINPen-sci plasma jet is a factor of two higher than in the effluent of the COST-Jet. The distribution of H2O2 in the COST-Jet effluent is initially highly uniform and suggests negligible mixing of H2O2 with the ambient air up to 15 mm from the jet nozzle, although it is rapidly diluted at further distances. In the case of the kINPen-sci plasma jet, the number density of H2O2 has a more pronounced radial distribution close to the nozzle, while the mixing with the ambient air is more gradual at further distances from the nozzle. It is evident that a detailed understanding of the H2O2 production in the plasma source, as well as of the transport of H2O2 to the substrate through the effluent, is required in order to optimise the intended effects. This work serves to highlight the difference of the distinct spatial distribution of H2O2 in the effluent of both types of plasma jets when considering their direct application in biomedicine.

Ozone production by an He+O2 radio-frequency atmospheric pressure plasma jet driven by tailored voltage waveforms

“…Non-thermal, atmospheric pressure plasmas have garnered considerable interest in recent years as efficient sources of reactive oxygen and nitrogen species (RONS), with applications spanning the fields of medicine, materials processing, green industry, and agriculture [1][2][3][4][5]. In particular, atmospheric pressure plasma jets (APPJs) are versatile instruments that are operated in open air and at close to room temperature for the direct delivery of RONS to a substrate [6][7][8][9][10][11][12][13][14][15]. One such RONS is ozone (O 3 ).…”