O COST-Jet with and without Solid Targets*

Non-thermal plasmas (NTPs) have the capability of delivering immunostimulatory reactive oxygen and nitrogen species (RONS). However, NTPs complex chemical mechanisms pose challenges in isolating the specific contributions of individual RONS to the desired effects. Therefore, it is crucial to precisely measure and map RONS spatial distributions both with and without targets, to optimize their diverse application. This utilizes a combination of planar laser-induced fluorescence (PLIF) and planar photofragmentation laser-induced fluorescence (PPF-LIF) techniques to image the spatial distributions of three key reactive species - the hydroxyl radical (OH), hydrogen peroxide (H₂O₂), and the hydroperoxyl radical (HO₂) - in the effluent of a humid-Helium driven Capacitively Coupled Atmospheric Pressure Microplasma Jet (COST-jet). The resulting 2D profiles of these species will be investigated when the jet propagates into open atmosphere vs impinging on solid targets. Calibration methods used to quantify the PLIF/PPF-LIF signals and differentiating between H₂O₂ and HO₂ will be discussed as well as the observed formation of chemical reaction fronts where the jet effluent mixes with the surrounding atmosphere. This research enhances our understanding of OH, H₂O₂, and HO₂ in the jet effluent, bringing us closer to deciphering the complex plasma chemistry interactions required to advance medical applications and customize the deliverable densities of essential reactive species.