Study On 3D Printing Process Of Poly(ε-caprolactone)-hydrogel Composite Scaffold

3D bioprinting is a technology that prints "bio-ink" mixed with living cells layer by layer to form a three-dimensional structure.The printed structure not only can be used in tissue engineering,cell culture with 3D scaffold,drug screening,but also provides a new direction for artificial tissue and organ production.Therefore,the 3D bioprinting is one of the most cutting-edge and research-valued fields in the 3D printing technology research.In the past decades,3D bioprinting technology has continued to develop.However,due to factors such as materials and processes,the resolution and quality of printing cannot be satisfactorily achieved,leading to the vague vision of achieving functional tissue and organ printing.Polycaprolactone-hydrogel composite scaffold is a common application for 3D bioprinting.This work seeks to improve the print resolution and quality of this composite scaffold.In this article,a high-precision multi-material 3D bioprinting system based on the modular design concept was first designed and manufactured.Its mechanical structure,hardware circuit,control software and slicing software were all designed to meet the multi-material 3D bioprinting requirements.On this system,this research combined simulation with experiment to optimize the process of fused deposition modeling(FDM)printing of polycaprolactone(PCL)and motor assisted microsyringe(MAM)printing for alginate(SA)hydrogels.Series of exploration work were carried out,and finally high-precision 3D printing of the polycaprolactone-hydrogel composite scaffold was successfully achieved.This project established a FDM heat flow model and used simulation method to perform numerical analysis.It was found that the fluid-solid coupling interface morphology of the nozzle melt was a key factor in determining the smoothness of printing and print quality.It was studied how the process parameters such as the wind speed caused by fan,heating tube temperature,the nozzle aperture and the like affected the print quality of PCL.The best value of these parameters were found and verified by experiments.In addition,SA/CS/GDL solution with different compositional proportions was selected as injectable hydrogel material.The regression analysis was carried out to summarize the logistic relationship between the squeezed force and the time during solution’s chelation process.According to the experimental results,the variable-speed injection control algorithm based on time-varying pressure compensation was proposed to optimize the process parameters of the MAM nozzle.Experiments on monofilament tensile test,mesh printing experiment and composite scaffold printing showed that the performance of the multi-material 3D bioprinter designed in this work and the process improvement methods studied on this basis were all feasible and effective.Polycaprolactone-hydrogel composite bioscaffolds with high resolution can be manufactured by means of the method mentioned in this article,which will play a positive role in promoting the 3D bioprinting of functional tissues and organs.