Gelatin-based Composite Hydrogel Extrusion 3D Printing Performance Study

3D bioprinting is an emerging research field that integrates 3D printing technology with mechanical,material and biomedical disciplines to produce personalized and specific cell scaffolds,tissues and even organs in a precise and rapid manner.Due to the special nature of printing technology,3D bioprinting requires special and strict requirements for printing material bioink,and hydrogel is widely used in the field of tissue engineering due to its good biocompatibility and excellent shear thinning properties.In this thesis,based on the requirements of extrusion 3D printing technology for molding performance,we prepared a gelatin-based composite hydrogel with gelatin as the matrix and oxidized nanocellulose,glycerol and sodium alginate as multifunctional co-solvents,and formulated the most suitable hydrogel for extrusion 3D printing by changing the ratio of each material.The main work of this thesis is as follows:(1)The definition of extruded 3D printing molding performance is systematically analyzed.Based on the results of the analysis of the key influencing factors of hydrogel molding performance,a design method to improve the hydrogel molding performance of extruded 3D printing is proposed from three aspects: bio-ink,printing process and printing structure.(2)Simulation and experiments are conducted for the printing process involved in the internal flow of hydrogel in the nozzle and the external flow process,and the simulation results such as the average flow velocity and velocity flow field distribution at the nozzle outlet are brought into the actual printing test to build up a systematic printing process parameter determination method and provide a solution for the determination of the printing process parameters of each formulation of hydrogel.(3)The properties of gelatin-based composite hydrogels with gelatin as the matrix and oxidized nanocellulose and glycerol as the multifunctional co-solvent were investigated to reveal the optimal hydrogel formulations.The hydrogel formulation GTG30 has a loose and porous internal structure with a pore size range of 200-300 μm and a maximum compressive strength of 403 k Pa.It has good molding performance in three aspects: rheological properties,filament fidelity and structural integrity.(4)The molding performance of GTG30 was tested,and it was found that the hydrogel of this formulation showed a certain degree of structural collapse during the printing process,and there was room for improvement in structural integrity.The addition of 1% w/v sodium alginate to the GTG30 formulation was found to improve the molding performance of the hydrogel.In a series of printing tests,it was found that the new formulation GTGS30 could increase the maximum compression strength up to 446 k Pa,with higher filament fidelity and structural integrity,as well as the ability to print complex structures,resulting in better overall molding performance.