Evidence, origin and impact of liquid flows in plasma medicine in vitro treatments with APPJs

Abstract

Abstract Plasma jets are being intensively studied for biomedicine applications but their fine control remains challenging due to the mutual interactions between plasma and target. Even considering one of the simplest scenario in a research laboratory, using a plasma jet to treat a 2D cells culture in a plastic multi-well plate, it is not known in detail how the physical environment of the micro-well may influence the nature of the plasma jet treatment. This study aims to shed light by investigating for the first time the liquid flows induced by the plasma treating a biologically-relevant liquid (e.g. PBS) in standard tissue culture grade multi well plates (i.e. 96, 24, 12 and 6 wells). Evaporation, induced by the anhydrous gas flow, is demonstrated to govern the thermal effect and be at the origin of the observed liquid cooling. Moreover, the formation of stable vortexes in the liquid induces a non-uniform distribution of plasma generated reactive species. This phenomenon, reported for various vessels and volumes of liquid, does not originate from thermal gradients but is instead the likely result of a combination of electrohydrodynamic forces and gas flow tangential components induced by the plasma impinging on the liquid surface.