Análise termográfica dos efeitos diretos de jato de plasma atmosférico com diferentes ponteiras de fulguração

Abstract

The atmospheric pressure plasma jet (APPJ) has been consolidated as a promising technology due to its structural simplicity, low energy consumption, and ability to generate abundant reactive oxygen and nitrogen species without the need for vacuum systems. It has applications in various fields, particularly in medicine, for sterilization, wound healing, and surface modification processes. However, the understanding of the direct thermal effects of this type of plasma on biological tissues remains limited, which is a crucial factor for ensuring the safety and effectiveness of future clinical protocols. This study aimed to evaluate the temperature variation caused by the direct contact of plasma jets generated by direct current (DC), alternating current (AC), and radiofrequency-based devices, considering the geometry of the applicator tips used on different ex vivo biological tissues. Plasma was applied continuously for seven minutes on three types of ex vivo biological tissues: pig skin, bovine liver, and chicken skin. Different applicator tips were employed in association with three plasma devices: PLASMED (DC), PLASMAX (AC), and NIOO (AC), maintaining an approximate distance of 1 mm between the jet outlet and the sample surface. Thermographic data were acquired using a FLIR T540 infrared camera, and the images were subsequently processed with software developed in MATLAB to record minimum, mean, and maximum temperatures at 60-second intervals. The results showed that the thermal response depends simultaneously on the type of tissue, the tip geometry, and the plasma source. The DC device exhibited more stable temperature variation profiles, while the AC-based systems demonstrated greater thermal variability. Applicator tips with smaller contact areas, such as needle-type tips, concentrate energy and produce higher initial temperature rises, especially in thinner tissues, like chicken skin. Conversely, tips with more rounded geometries promoted more uniform heating, reducing the occurrence of temperature peaks. Among the tested tissues, bovine liver exhibited a more stable behavior and higher mean temperatures, which can be attributed to its higher water content. In contrast, pig skin showed a greater thermal amplitude, and chicken skin demonstrated higher susceptibility to oscillations. It can be concluded that the thermal variation induced by atmospheric plasma is multifactorial, resulting from the interaction between the energy source, the tip geometry, and the physicochemical properties of the target tissue. These findings highlight that the safety of biomedical plasma applications cannot be defined solely by device power but requires the standardization of application conditions.