Design And Experimental Study Of Precision Injection And Deposition System For High Viscosity Biomaterials

Bio-3D printing technology is a multidisciplinary technology that has emerged in recent years.It is a technology that prints out the required tissue model by moving the nozzle which can eject the bio-ink through the movement of the three-dimensional platform.Current bio-3D printing is generally printed by the way of extrusion.Extrusion printing can print high-viscosity materials,but the filament condition is limited by viscosity.When the viscosity is high and the viscosity is low,it is not easy to form silk.The printing viscosity range is limited..And it is difficult to print complex 3D models.In order to solve the above problems,some people use the ondemand injection method,which can print higher precision models,but their nozzles are mostly purchased commercial printer inkjet nozzles,with low power,limited printing materials.Therefore,the purpose of this paper is to design a valve-controlled eject head that can print high-viscosity materials and can print high-precision models.First,the theory design was carried out with a valve head with higher power.And the nozzle was studied from three aspects of kinematics simulation,fluid simulation and electromagnetic simulation.The possibility of printing tiny droplets was analyzed.The influence of some parameters such as striker displacement,spring stiffness,spring preload,feed pressure,nozzle diameter,nozzle length,wall clearance,cone angle,fluid viscosity,coil window height,ampere-turn,striker and static iron core radius on nozzle design and droplet formation were obtained.Based on the simulation research,the electromagnetically driven valve-controlled nozzle was designed and developed.The required experimental system including the electronic control system based on STM32 single-chip microcomputer to realize PWM control,the air pressure control with resolution of 0.0001 Mpa,a threedimensional motion platform with absolute positioning accuracy of 20?m and a droplet detection system capable of detecting droplet volume and droplet velocity was builded,which provided conditions for experimental research.Finally,the experiment studied the effects of different conditions on the droplet injection of sodium alginate.After compared with the simulation,the conditions for successful droplet discharge,the method of printing the smallest droplets,and the method of obtaining the required droplet size by controlling the feed gas pressure were obtained.And the relevant process parameters of the printed 3D model were explored,which were applied to the printing of collagen materials.The effect of various parameters on collagen printing was studied.