Research On 3D Printing Process And Mechanism Of Tough Hydrogel

Hydrogels have found their promising applications in biomedicine,intelligent materials,new sensors and other fields due to their unique mechanical properties and remarkable biocompatibility.Recently,due to the development of various tough hydrogels,the mechanical properties of hydrogels have been significantly improved,which also highly extends their application.However,due to the complicity of the crosslinking process of tough synthetic hydrogels,the hydrogels generally have poor formability and processability,and cannot be used to prepare complex functional structures or devices through traditional processing techniques.Fortunately,the rapid development of 3D printing technology brings a new method for hydrogel processing,which helps solving the problem of manufacturing complex hydrogel structures.Nevertheless,there are still lots of challenges of applying 3D printing technology to the preparation of tough hydrogels.Therefore,in this thesis we mainly studied the 3D printing of a new type of highly tough hydrogels,including the synthetization of hydrogel,development of 3D printing platform,investigation of hydrogel printability and hydrogel curing mechanism.Firstly,we synthesized a polyion complex(PIC)gel,based on poly(3-(methacryloylamino)-propyl-trimethylammonium chloride)/poly(sodium pstyrenesulfonate)(PMPTC/PNaSS)hydrogel.Here,we improved the synthetic process by reducing the internal defects and obtained the PIC gel with better mechanical properties.Rheological behaviors of PIC solutions and tensile strength,Yong's modulus,fracture strain and fracture energy of molded PIC hydrogels were tested,which helps developing and understanding of 3D printing of PIC hydrogels.Then,a 3D printing platform with an extrusion system was developed for 3D printing of PIC hydrogels.In this part,printability of PIC hydrogel,spatial resolution and mechanical properties of printed hydrogels were investigated systematically.Moreover,the rheological properties and curing rate of PIC solution were investigated and used to explain the experimental results of PIC hydrogel printing performance.At the last of this part,several complex two-dimensional and three-dimensional structures were printed using PIC hydrogels to demonstrate the excellent processability of PIC hydrogels.Also,the 3D printing of spider web was introduced to exhibit the practical application of PIC hydrogels.At last,the diffusion based-curing behavior of PIC hydrogels was studied.The diffusion of water molecules into hydrogel solutions and the diffusion of NaCl into water were found to lead to the curing of the PIC hydrogel.The one-dimensional diffusion of water and NaCl ions with different polymer concentrations of PIC hydrogel was experimentally investigated to measure the curing rate of PIC hydrogels.After that,a physical model was proposed to study the curing mechanism of PIC hydrogels.Based on the numerical results,the curing mechanism of PIC hydrogels and the effects of polymer concentration were discussed.