Investigation On Multi-nozzle 3D Bioprinting System Based On Pneumatic Extrusion Deposition Technology

As a component and functional carrier of tissue engineering,biological scaffolds have a direct impact on the repair and regeneration of damaged parts of patients.Due to its own limitations,the traditional scaffolding methods of tissue engineering have not been able to meet the growing requirements of tissue engineering for the development of biological scaffolds.3D Bioprinting technology is based on the principle of "discrete-stack",which can accurately deposit "biological ink" in space.It has unique advantages in preparing highbionic tissues and organs.The single-nozzle 3D Bioprinting system has been difficult to meet the requirements for the formation of biological scaffolds.Therefore,it is of great significance to develop the multi-nozzle 3D Bioprinting system.Based on the principle of pneumatic extrusion deposition technology,the paper develops a multi-nozzle 3D Bioprinting system.The paper completes the development and construction of the entire system,and uses the completed printer to conduct research to verify that the printing system is reasonable,stability and feasibility.Main tasks as follows:(1)Based on the 3D Bioprinting technology background and the requirements of tissue engineering biological scaffold formation,the functional requirements analysis of the multi-nozzle 3D Bioprinting system is performed,and the expected design goals and design requirements of the printing system are proposed.The overall design plan is determined.The entire system is divided into three parts with modular design ideal: mechanical system,control system and control program.The design parameter requirements according to the actual application requirements are determined.(2)Mechanical system is divided into four parts: three-dimensional motion platform,print head,feeding system and work table.The combination form of the three-axis motion and the motion design of the platform using the transmission method of servo motor and ball screw are determined.Two specifications print heads which can be assembled by users as required are designed.The two-way ball screw device as a multi-nozzle switching transmission structure is adopted.It can converts multi-nozzle printing into multiple singlenozzle and turns to be called on demand.The feeding system of the four gas lines are designed and the gas lines are independent from each other.The "S"-shaped groove is designed inside the work table,and the liquid cooling method is adopted to achieve the cooling purpose.The 3D assembly of the multi-nozzle 3D Bioprinting system is completed by using NX with four commonly used multi-nozzle combination methods.(3)Control system is divided into four parts: motion control,temperature control,solenoid valve control and control program.The working principle of stepper motor and servo motor is analyzed.Five-axis coordinated motion control is achieved by using two MPC08 SP motion control cards.Polyimide heating film and semiconductor cooling sheet are selected to heat and cool the printhead separately to realize the integrated cooling and heating function of the printhead.The suitable type of low-temperature coolant circulation pump is selected to adjust the temperature of the work table.The general-purpose I / O expansion board is used to open and close the solenoid valve to complete automatic control of gas circuit on / off.The control program is independently developed by the laboratory.It completes the pre-processing and printing process control of the printing model and realizes multi-nozzle coordinated printing.(4)Experimental study on Multi-nozzle 3D Bioprinting system are tested.The completed printing system was used to analyze the effects of the main process parameters such as the print head temperature t,the table temperature T,the print head pressure P,the print speed Vxy,the print layer height H,and the nozzle height h in the molding process.The printing system scheme designment and the rationality of component selection are verified.The single-nozzle print molding experiments of three-dimensional brackets of four materials are performed.The results show that the developed printing system has good stability and control performance,and can be used for printing of various materials.The multi-nozzle three-dimensional bracket printing molding experiment and the special-shaped multi-nozzle printing experiment are performed by using the same four materials.The results show that the printing system developed in the paper can accurately deposit the spatial positions of multiple materials in X-Y-Z space.It realizes the multi-nozzle printing with the ability to build complex structures of multiple materials.