Research On Manufacturing Method And Application Of Fine Silver Grid Based On Ring Electrode Electric-field-driven Jet 3D Printing

Transparent electrodes,the thin-film electrodes with good photoelectric properties(transmittance and conductivity),have been widely used in touch screens,thin-film solar cells(OSCs),OLEDs,and transparent displays.At present,indium tin oxide(ITO)transparent electrode is one of the most popular in the industry,however,ITO is costly and difficult to bend,it cannot be used for flexible transparent electrodes.Compared with ITO,silver grid transparent electrode not only has good photoelectric performance,but also has outstanding advantages such as strong flexibility and low price.However,how to achieve low-cost mass production of high-resolution(high light transmittance)metallic silver grids is a challenging for the academic and industrial circles.Here,we designed and proposed a new printing method ring electrode electric-field-driven jet 3D printing technology,which provides a feasible method for stable printing of high-resolution silver grids.This paper mainly introduces the aspects of principle introduction,simulation,experimental research,etc.The innovation points and the completed work are mainly as follows:(1)This paper proposes a 3D printing technology of ring electrode electric-field-driven jet 3D printing method,which is different from the counter electrode of traditional electrohydrodynamic(EHD)jet printing and the single nozzle electrode of existing electric-field-driven jet 3D printing in our laboratory.This technology eliminates both the substrate electrode and the nozzle electrode.The metal ring fixed on the outside of the insulated nozzle is used as the extraction electrode,which is connected to a high-voltage power supply to form the self-excited electrostatic field,providing the electric field force required for 3D printing.Therefore,the printing material and the electrode are no longer in direct contact during the printing process,avoiding the repulsion and interference caused by the residual charge transferred from the power source to the printing material in the traditional EHD jet printing.At the same time,the nozzle and the substrate material are not restricted,insulating nozzles do not require cumbersome conductive treatment.In view of the above printing principle,the nozzle system is designed,the self-made glass nozzle is coaxially sleeved on the outside of the commercial stainless-steel nozzle,and a metal ring is installed on the outside of the glass nozzle as the extraction electrode.The feeding system is optimized and connected in the air supply module.The two-position three-way electromagnetic reversing valve uses the reversing valve to quickly release the high-pressure gas in the trachea after the high pressure pushes the printing material to overcome the capillary force of the glass nozzle tip,and quickly reduces the pressure in the pipe to ensure the stability of the material supply.(2)This technology is studied through simulation and comparative experiments.The simulation results prove that the electrostatic field can be formed between the ring electrode and the substrate under different substrate conditions.At the same time,the material and size parameters of the metal ring electrode are optimized,and the material is determined to be copper.The smaller size of the ring electrode provides the stronger field strength.The parameters of ring were chosen to be thickness of 0.05mm,length of2mm,distance to the substrate of 2mm.Experimental results prove that,compared to traditional EHD jet printing technology,this technology can print conductive materials(silver paste)on conductive substrates(silicon wafers)without discharge,and can achieve stable printing of small-pitch lines,such as the silver lines with line width of 20?m,the pitch of 5?m,and the photoresist line with line width of 5?m,the pitch is 10?m.(3)In order to apply this technology to the production of silver grids,the influence of process parameters on the results was studied and optimized.Experimental data shows that when the voltage increases from 540V to 615V,the line width increases from 0.8?m to 4.2?m.When the voltage is too high,the stability of the Taylor cone is destroyed and the appearance of the silver wire becomes worse.When the air pressure increases from14kPa to 22kPa,the line width is increased from 1.7?m to 5?m.When the air pressure is too high,too much material will cause larger droplets in the printed result;when the frequency is increased from 600Hz to 2000Hz,the line width is reduced from 6.1?m to0.4?m.When the frequency is too high,the amount of charge accumulated on the meniscus in each cycle is too small to maintain a stable Taylor cone,and the printing result is discontinuous.When the printing height increases,the line width first decreases and then remains unchanged.When the movement speed of substrate increases,the line width continues to decrease.The final parameters are determined as:voltage 565V-615V,frequency 1000Hz,air pressure 14k Pa-22k Pa,printing height 40?m,substrate moving speed 0.5mm/s-3.5mm/s.Through this process parameter window,a silver wire with a line width of 300nm-7?m and aspect ratio of 0.39-1 was produced.(4)Typical application cases:In order to demonstrate high-resolution manufacturing capabilities,based on the optimized process parameter window and the comprehensive consideration of the transmittance and conductivity,a line width of 3.5?m,a period of90?m,a square resistance of 1.34?sq^-1,and a light transmittance of 92%(550nm wavelength).Under 3V voltage,the high temperature can reach 85?in 20s.On the other hand,in order to present the ability of small pitch of printed structure,interdigital electrodes with line width and pitch of 15?m are produced,which have been used for the detection of drinking water containing copper ions.the detection limit of this interdigital electrode is 10nmol/L-1?mol/L.