Experimental Research On Electrohydrodynamic Printing Of PAN And PVA Polymers

As a technique based on electrohydrodynamic theory,electrohydrodynamic printing(EHD)uses a high voltage to stretch the liquid out of the nozzle tip to the Taylor cone and form a charged jet at the tip of the Taylor cone.It has the advantages of low cost,high efficiency,and on-demand manufacturing and has great application prospects in electronic circuits,micro-nano sensors and biofilms.Aiming at the demand of PAN and PVA polymer micro-nano structure manufacturing,the EHD printing process of the polymer materials was studied.Aiming at the need of medical hemostatic materials manufacturing,an EHD printing platform was built to explore the relationship between printing parameters of PVA solution and the diameter,and hemostatic test was carried out to verify the hemostatic effect of the membrane.An experimental platform of coaxial focusing EHD printing was built,and the printing characteristics of PAN solution and the subsequent nanowire processing technology were studied.High-voltage power supply,micro-injection pump,displacement platform and other equipment were integrated,and an EHD printing platform was built for the manufacture of medical hemostatic film.A liquid electrode was designed and manufactured to improve the instability of jet whipping caused by Coulomb force.Substrate support device was reformed,and high temperature resistant materials such as polyimide were used to reduce weight and platform load.Flexible adjustment of substrate position and temperature during printing process was realized,and a coaxial focusing EHD printing experimental platform was built.PVA solution was chosen as the printing solution,added a small amount of aldehyde-based dextran(PAD)and kaolin.The medical hemostatic membrane that can be used to control the bleeding was fabricated,using the technology of EHD writing,and the printing parameters were also explored.It has been found that the process tends to be stable with the increase of voltage.However,when the voltage is too large,the jet oscillates violently and even breaks down.As the flow rate and the concentration of the solution decrease,the diameter of the fiber also decreases.A medical hemostatic membrane with a large pore diameter was prepared by using gauze with a pore diameter of 500?m as a receiving device.The biological hemostasis experiment was carried out,and it was found that the PVA/PAD/kaolin hemostatic membrane can effectively improve the blood coagulation speed and has a good hemostasis effect.Coaxial focused EHD printing experiments were carried out using the EHD printing platform.The PAN solution was first prepared and the effects of printing parameters on the printing process and results were investigated.It is found that as the voltage increases,the jet scale decreases gradually,and the whip amplitude becomes larger until the discharge breaks down.As the flow rate and needle size decrease and the printing speed increases,the scale of the printing results decreases.PAN was used as the inner functional liquid,and silicone oil was the outer high viscosity protective liquid.The PAN nanowire with a minimum diameter of 100 nm was printed and then sintered into carbon nanowire with a minimum diameter of 75 nm.A silicon substrate with a channel of 2?m to 10?m was fabricated by photolithography,wet etching,and a PAN nanobeam having a minimum diameter of 110 nm was printed on the substrate.