Simulation And Experiment Of Microplasma Jet Etching Based On Fluid-assisted Focusing

Atmospheric pressure cold microplasma jet（APμPJ）is a new type of low temperature plasma generation technology.It gets rid of the limitation of a vacuum environment,and has the advantages of low temperature,low cost,high concentration of various active substances,simple equipment,no special requirements for operating environment,etc.,which makes it one of the hot topics of current research.The results have shown that the plasma jet has an extension phenomenon on the surface of the material to be etched during the etching process,resulting in the actual contact line width being much larger than the jet diameter in the free state.It seriously affects the machining accuracy,increases the difficulty of jet control,and directly affects the etching rate and etching effect.In this paper,by establishing the fluid dynamics model of APμPJ and the diffusion-limited etching model,the molar concentration distribution and velocity change of working gas under the action of shielding gas,as well as the etching process and final etching morphology of active particles,are analyzed respectively.The main work contents and conclusions are as follows:（1）APμPJ generator is designed and constructed,which mainly includes equipment selection of gas delivery system,control system,test system and discharge system,design of discharge electrode and construction of discharge device.Through testing experiments,reasonable working gas and shielding gas are selected.（2）A fluid dynamics simulation model of APμPJ is established.The simulation model established by COMSOL is used to explore the effects of shielding gas flow rate,distance difference between inner and outer tubes,and outlet shape of shielding gas outer tube on the molar concentration distribution and gas velocity of the working gas.By analyzing the concentration distribution of the jet on the substrate,the focusing effect of the shielding gas on the jet is further explored.The results show that under the action of shielding gas,the greater the N₂ flow rate and the distance difference,the stronger the focusing effect;the larger the outlet shape,the weaker the focusing effect.（3）A diffusion-limited etching model of the plasma jet is established.Based on MATLAB software,the diffusion process of active particles on the surface of the material to be etched and the evolution of etching morphology,as well as the influence of model parameters such as move probability and diffusion coefficient on the etching results are simulated.The etching results are characterized by contact line width and etch depth.The results show that the etching process with active particle diffusion is more suitable for the actual etching situation.At the same time,the greater the move probability,the greater the etching depth;the greater the diffusion coefficient,the greater the contact line width.（4）Taking polyethylene terephthalate（PET）film as the etching sample,the verification experiment of fluid-assisted focusing etching of polymer film is carried out.The parameters in the above numerical simulations are experimentally verified by the single-variable method.Based on the action of shielding gas,the influence of shielding gas flow rate,distance difference between inner and outer tubes,outlet shape of shielding gas outer tube,and working voltage on the contact line width of jet and etching depth are analyzed.The results show that the experimental results are highly similar to the numerical simulation results,which verifies the accuracy and feasibility of the numerical simulation results.In this paper,a fluid dynamics simulation model and a diffusion-limited etching model of APμPJ are established.The effects of different process parameters on the focusing effect and etching morphology under the action of shielding gas are analyzed,and the evolution of active particles during the etching process is analyzed.The feasibility and accuracy of the simulation and model are verified by experiments.This paper can provide a reference for the in-depth study of the fluid-assisted focusing effect of shielding gas and realize the high-precision and controllable processing of polymer films.