| Electrohydrodynamic jet printing(E-jet printing)has the advantages of high resolution,wide materials adaptability and no "Coffee ring" phenomenon.It has great potential in the field of micro nano 3D manufacturing,especially in the field of flexible electronic manufacturing,and has developed rapidly in recent years.At present,most of the applications of E-jet printing are single nozzle printing,which has low efficiency.The use of multi-stage nozzle array printing is an effective way to improve the printing efficiency.There is electric field interference between multi-stage nozzles,which will affect the printing accuracy and is difficult to guarantee,and the higher the voltage,the more serious the electric field interference;Therefore,seeking a more friendly nozzle type with voltage conditions and a reasonable multi-stage nozzle array structure is the key to improve the printing efficiency while ensuring the printing accuracy.To solve the above problems,this work aims to find a more voltage friendly nozzle type and a reasonable multi-stage nozzle array structure.Through the combination of theoretical analysis and numerical simulation,this paper studies and designs a multi-stage nozzle array structure with better electric field uniformity,and uses intelligent optimization algorithm to optimize the design structure.The design results and relevant conclusions have engineering application reference value and practical significance for the multi-stage nozzle array of E-jet printing.The specific research contents and results are as follows:1.The basic principle of E-jet printing is expounded,and the influencing factors of E-jet printing jet stability and various modes of E-jet printing jet are discussed;The flow field,electric field control equation,multi physical field coupling method and two-phase flow interface tracking method required for the finite element numerical simulation of E-jet printing jet are discussed2.Through COMSOL multiphysics multi physical field simulation software,the simulation models of conical jet evolution process of conductive nozzle and insulating nozzle with the characteristics of restraining Taylor conical reflux are established.The correctness of the model is verified by comparing the evolution form of conical jet with Collins model,and the working stability of the designed insulating nozzle is explained by charge distribution.Finally,the influence laws of key process parameters such as voltage,jet height,nozzle inner diameter and inlet pressure on the state of conical jet are summarized.The research shows that the designed nozzle has good electric field performance and long-term stable working ability;When the stable jet is realized,the excessive voltage is easy to make the jet unstable and multiple jets appear;When the jet height is too high,the space intensity is too low to form a jet;The increase of nozzle inner diameter and inlet pressure can accelerate the jet forming speed,but the taper of Taylor cone also increases,which increases the jet instability.It is necessary to increase the voltage to ensure its stable state.3.For the design of insulated nozzle,the electric field simulation analysis of multi-stage nozzle linear array and annular array is carried out.The influence of electrode voltage,nozzle spacing and jet height on the electric field uniformity of linear array and annular array is analyzed by single factor analysis method.Taking the standard deviation of electric field intensity as the evaluation index,it is verified that the uniformity of electric field distribution of annular array is better.The suppression effects of different jet height method and multistage voltage method on the "Edge effect" in annular array are discussed;The results show that the reasonable use of the two methods can suppress the electric field interference in the ring array and improve the uniformity of the electric field;The equipment of different jet height method is relatively simple,but it will damage the printing resolution.The printing resolution of multi-level voltage method is high,but the control is difficult and the equipment is complex.In the actual printing,it needs to be selected according to the printing needs.4.Taking the standard deviation of electric field intensity of ring array as the optimization objective,the key parameters of ring array are optimized.Through the design expert software,four factors are selected for the experimental design: the peripheral nozzle voltage,the voltage difference between the central nozzle and the peripheral nozzle,the nozzle spacing and the jet height.The response surface method is used for quadratic term fitting to obtain the relationship model;The key parameter combination of ring array is optimized by Strengthen Elitist Genetic Algorithm(SEGA);Compared with the optimization results of Simple Genetic Algorithm(SGA),the optimization effect of SEGA is verified;The parameter combination optimized by SEGA is verified by finite element simulation.When the peripheral nozzle voltage is 1.4k V,the voltage difference between the central nozzle and the peripheral nozzle is 160 V,the nozzle spacing is 1 * dr and the jet height is 0.65 mm,the standard deviation of the electric field intensity is 0.744.Compared with the results optimized by Sega,the relative error between them is only2.42%.The optimization result is reliable and the electric field uniformity of the annular array is further improved. |
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