A comparison of different cold atmospheric pressure plasma jets for biomedical applications : gas temperatures, morphology, power dissipation and biological activity

The goal of plasma induced healing is to obtain a high bacteria killing rate without significant damage of the healthy cells. For this task various cold atmospheric pressure plasma jets (APPJ’s) have been developed over the years. In those APPJ’s the plasma is created with an inert gas inside a ceramic or glass tube between two electrodes. The effluent mixes outside with the air-environment. APPJ’s differ usually in electrode geometry (ring, needle), used gas-effluent (helium, argon) and excitation frequency (DC, kHz, MHz). These differences in input parameters are also changing the plasma parameters, such as the gas temperature, UV-emission and production of reactive species, which makes a direct comparison of the plasma jets challenging and contributes to the large discrepancies between biomedical experiments of different groups using (slightly) different plasma jets1. Additionally the plasma is also strongly influenced by the sample which is treated, due to the change in conductivity and capacitance which adds to the complexity. We investigate therefore also the plasmas in contact with saline solutions, which are representative for a wound. In this contribution we use one plasma jet, a plasma needle and operate it with helium and argon with mixtures of air and three different excitation modes, namely nanosecond pulsed DC, kHz pulsed radio-frequency and continuous radiofrequency. We investigate the difference of power dissipation of the plasma and spatial resolved gas temperature for the different conditions. Furthermore we investigate the dependence of these parameters when in contact with metal, ceramic and saline solution. For the pulse excited plasmas nanosecond time resolved images have been obtained to gain more insight on the morphology of those discharges when in contact with a saline solution. Preliminary results on cell and bacteria-treatment with the different plasmas are also discussed. 1. J. Ehlbeck et al., "Low temperature atmospheric pressure plasma sources for microbial decontamination," J. Phys. D: Appl. Phys., vol. 44, no. 1, p. 013002, Jan. 2011. ___________________________ * This work is part of the research program of the Foundation for Fundamental Research