Research On Electric-field-driven Jet Deposition 3D Printing Technology

There is a very wide range of scientific and practical engineering needs for multi-material and multi-scale structures in the fields of new materials,the tissue engineering,bionic structures and software robots.It is urgent to develop new reliable process for integrated manufacturing of multi-material and multi-scale complex structure.In this paper,an electric-field-driven(EFD)jet deposition printing has been proposed to implement multi-scale and multi-material additive manufacturing with high resolution and efficiency as well as low cost.Systematic researches,which involved theoretical analyses and numerical simulations and experimental explorations,have been carried out.The main research work and innovation are as follows:(1)This paper presents an electric-field-driven jet deposition 3D printing technique which is based on electrostatic induction and electrohydrodynamic cone-jetting behavior.The EFD jet 3D printing only requires a conductive nozzle connecting the anode of high-voltage pulse power,the ground electrode(conductive substrate)is no longer pre-requisite.The electric field required for the ejection is generated by the electrostatic induction between the conductive nozzle and the target substrate.With the new way of generating electric field,the EFD jet deposition 3D printing breaks through of the constraints of the E-jet printing and possesses some distinct strengths and unique capabilities which include the independence of used substrate(evenness,conductivity,etc),larger height of printed objects,suitable for various solutions and melted materials with ultrahigh viscosity,macro/microstructures multi-scale fabrication.(2)Taking into account both printing accuracy and printing efficiency,two novel working modes,pulsed cone-jet mode and continuous cone-jet mode,are proposed for implementing multi-scale 3D printing.The influences of the process parameters(voltage,air pressure,pulse duration time,translation stage speed,etc.)on the printed results are investigated in two working modes.In the pulsed cone-jet mode,the air pressure and pulse duration time have a more prominent effect on the printed dot diameter as compared to the applied voltage.In the continuous cone-jet mode,the line width increases with the increase of the air pressure and decreases with the increase of the stage speed.The voltage amplitude has little influence on the printed line width but determines the start of the continuous jetting coupled with the air pressure(3)We have established a mathematical model for EFD jet deposition 3D printing,and analyzed the multi-physics coupling process in detail.The finite element simulation software(COMSOL MULTIPHYSICS)is used to simulate the electric field distribution and intensity around the nozzle and the ejection behavior.On the one hand,it shows that the new method can produce the stable electric field between the conductive nozzle and the target substrate.Since there is no electric conduction between the conductive nozzle and the target substrate,it enables the EFD jet deposition 3D printing to set a lower nozzle height to generate more powerful and stable electric field.On the other hand,it reveals the relationship between the flow field,electric field and charge density field in the process of liquid ejection.The surface charge at the meniscus accumulates under the action of the electric field,which causes the movement of the liquid and deforms the meniscus.Meanwhile,the change of the charge position causes the electric field to redistribute.The above process is cycled until the jetting ends.(4)The proposed technology has a strong universality for substrate(or printed object)materials and the print height and printed materials which is verified by experimental methods.Several typical patterns and structures are fabricated to display the capability and advantages of the proposed technique in manufacturing multi-scale and multi-material structures.A serial of variable width lines(5-100?m)is printed by the same nozzle with an inner diameter of 60?m.Using the melt electric-field-drive jet deposition 3D printing technique,we print a micro-scale structure with a high-aspect-ratio of 20: 1 and a 3D biological scaffold with high resolution.Combined with multi-nozzle technology,we successfully print out the 3D electronic structure products with multi-material and multi-scale features.