Synergistic effect of multi-parameters on NO density of a helium atmospheric pressure plasma jet in contact with skin

Nitric oxide (NO) is a crucial molecule for living organisms, which acts as a messenger in most mammalian organs. Fortunately, plasma jet can generate an abundant amount of NO. In this paper, the NO generated by a helium plasma jet when it is interacting with pig skin is diagnosed using laser-induced fluorescence (LIF) method. The multi-parameters' effect of the distance between the nozzle and the skin surface (distance d), the gas parameters (gas flow rate, O-2 and H2O percentage) and the applied voltage parameters (the amplitude and frequency of the voltage) on the NO density is explored. The results show that the NO density increases and then decreases as the gas flow rate increases. The gas flow rate corresponding to the maximum NO density is positively correlated with the distance d. In the case of high gas flow rate or small distance d, premixing a small amount of O-2 or H2O content lead to higher NO density. Higher voltage amplitude and frequency can increase NO density, but high voltage amplitude at high flow rate and small distance d lead to a decrease in NO density. The generation pathway of NO is mainly affected by N-2(A), N, O-2, O, OH, H and NO2, and the consumption pathway is closely related to the particles N, O, OH, O-3 and HO2. Among them, N and O atoms participate in both generation and consumption. Therefore, the synergistic effect of multi-parameters, the emergence of different effects is closely related to the synergistic effect of these two particles.