This study investigates the thermal behavior of conductive and nonconductive mesh substrates during exposure to a custom built atmospheric pressure plasma jet (APPJ). The jet operates using a coaxial dielectric barrier discharge configuration with a novel gas diffusing dielectric core. It is powered by a high frequency AC source operating at 21 kHz with a 33% duty cycle. The surface temperature was recorded in real time using a calibrated FLIR i7 infrared camera, a method increasingly used in plasma thermal studies for its noninvasive mapping of heat transfer. The following three parameters were varied: working gas (argon or helium), jet standoff distance (5–60 mm), and exposure duration (10–240 s). Identical stainless steel and polypropylene plastic meshes were used to compare thermal behavior under identical plasma exposure conditions. The results identify that the heat transfer and subsequent behavior is highly dependent on both gas type and the substrate conductivity. Helium plasmas produced higher relative peak temperatures than argon, particularly at short standoff distances. Stainless steel meshes demonstrated faster heating and steeper gradients, while polymer meshes showed slower heat accumulation and a wider thermal distribution. The heat transfer reduced significantly beyond a critical standoff distance (approximately 40 mm) due to jet divergence and reduced energy coupling. Using thermography, this work provides an understanding of plasma effects on mesh geometries. The findings are relevant to biomedical and industrial applications where porous or patterned substrates are common and thermal exposure is critical. They offer a basis for controlling APPJ treatments through the interplay of gas species, thermal conduction, and exposure geometry.
Lalor et al. (Mon,) studied this question.