Numerical study on propagation mechanism and bio‐medicine applications of plasma jet

Abstract

In this study, the propagation mechanism of plasma jet and some bio-medical applications are investigated by two-dimensional numerical model. The key equations of plasma physics and chemistry related with plasma jet are firstly introduced. The simulation results suggest that the sheath forms near the dielectric tube inner surface, which results in the plasma channel to shrink in the radial direction inside the dielectric tube. The photoionisation of air species plays a crucial role in the transition from the localised discharge to streamer. The Penning ionisation increases the electric conductivity of the plasma channel and facilitates the formation of ring-shaped plasma bullet. For the plasma jet in the open air, electronimpact dissociation of H 2 O, electron neutralisation of H 2 O + , as well as dissociation of H 2 O by O(1D) are found to be the main reactions to produce OH. For micro plasma jet, the higher ignition voltage as the tube diameter decreased is attributed to the deceasing pre-avalanche electron density inside the tube. The simulation of plasma treatment of bacteria biofilm indicates that the mean free path of charged species in µm scale permitted the plasma penetrate into the cavity of the biofilm, and the structure of the biofilm results in the non-uniform distribution of ROS and RNS. The simulation of plasma treatment of cells immersed in liquid suggests that the HO 2 generated by plasma aqueous species is the only way for superoxide to penetrate cell membrane and damage cytosolic fumarase B.

Ignition properties of helium discharges in dielectric tubes with radius from 50 µm to 3 mm

“…Atmospheric pressure low temperature plasma has shown great potential in various application fields including medical treatment and material processing . Typically, the dielectric barrier structure is used in the plasma devices to generate moderate discharge with abundant active species, while the conducting current and gas temperature remain low to avoid electric and thermal damages .…”

Physicochemical properties of the AC-excited helium discharges using a water electrode

“…-NO 2 induces cell apoptosis through DNA damages and can be employed for cancer therapy [20,21]; while -NO 3 is an important fertilizer for stimulating growth of plants [3,22]. From the aspect of fundamental studies on the discharge itself, the complicated physical-chemical processes involving water vapor with high concentrations at the gasliquid interface make the control of plasma key parameters and the formation mechanisms of primary species more challenging [7,9,23,24].…”

Interactions between multiple filaments and bacterial biofilms on the surface of an apple

“…The model uses a 2D finite element method to solve the plasma governing equations. The relevant equations used in the model are the same as those described in the literature [21,23]. The Poisson equation is used for the electric field in the whole computational domain, both the plasma area and the non-plasma area, therefore, the permittivity (ε/ε 0 ) and conductivity of the bacterial biofilms are necessary to input into the model.…”

“…The electron energy conservation equation computes the electron temperature. The three-term exponential Helmholtz model as referred in the literature [20,23,39] is solved for the photoionization source between N 2 and O 2 , due to photoionization playing an important role in the process producing radiation electrons in front of the plasma channels.…”

“…To give guidance to the experiment and realize good reproducibility of plasma sterilization ultimately, we attempt to simulate the process of streamer propagation and the interactions between plasma filaments and bacterial biofilms. Therefore, it is necessary to determine the key mechanisms of transportation and plasma chemistry with the help of other researchers' simulation models [18][19][20][21][22][23]. Babaeva et al presented a 2D simulation model to study the intersection between air plasma filaments and human skin with a small wound in the context of plasma medicine [15].…”