Analysis of atmospheric pressure plasma for biological applications

In the last 25 years the field of plasma medicine encountered a large growth. Different sources have been developed and studied, for different purposes: among them, in the Padova laboratories the Plasma Coagulation Controller has been ideated, designed and built. The biological effects of this helium-driven source have been observed both in antibacterial applications and in blood coagulation. As for other sources, the interaction between plasmas and biological substrates which leads to observed effects is a complex combination of different phenomena and actors; the totality of the processes is still far to be understood. Reactive oxygen and nitrogen species, generated in the interaction of plasma with atmosphere, are considered to have the main role in medical effects of plasmas: the aim of this thesis is to characterize the production of these compounds in the source, and its variation as a function of the power and environmental conditions. The species are measured using Fourier-transform infrared absorption spectroscopy, a technique which allows a precise and fast measurement of gases concentrations. The source is therefore adapted to the optical system, providing it with all the instruments necessary to control the atmosphere in which the plasma is generated; then, all the setup is optimized, minimizing the errors and the noise sources. As final results, the presence of ozone, nitrous oxide and nitric acid has been detected. Moreover, the variation in production of these species as function of the atmosphere humidity has been measured, proving that as the humidity rise, the production of ozone fall. Finally, the measured data are compared to theoretical models, finding compatibility.