The introduction of 3D printing in bioapplication is progressing fast due to its unique advantages. 3D bioprinting could be used in various medical applications such as tissue engineering, organ printing, cell-based sensors, surgical and diagnostic aids, and manufacturing of medically related products. Hydrogels have been used as bioinks due to their high biocompatibility, low toxicity, and high water content, making them similar to the extracellular matrix. Common hydrogels consist of different kinds of natural polymers, like alginate. For printing applications, these materials should have enough viscosity and shear-thinning behavior. Moreover, they should be able to crosslink with UV, heat, or ionic crosslinking. For increasing the structural fidelity of the hydrogels, another material should be added to them. Cellulose is one of the attractive materials for mixing with hydrogel due to its high hydrophilicity, biocompatibility, and mechanical properties coming from its high surface area. Because of these properties, hydrogels with alginate and cellulose are good candidates for using them in 3D bioprinting. In this research, direct ink writing (DIW) technology was used. Systems with hydrogels have high biocompatibility and show good enough structural fidelity. Rheological results show good enough viscosity and shear-thinning behavior of the hydrogel inks. Moreover, the printed models have good structural fidelity without any expansion. These results with high biocompatibility coming from hydrogel make synthesized hydrogel inks good candidates in tissue engineering applications.
Orthodontic application, printing organ models, and surgical aids are other applications of 3D Printing in biotechnology. For this application, photocurable polymers with higher thermomechanical properties and photocurable ability could be used for printing patient-specific models of different organs. In this research, systems with photocurable polymers were synthesized and printed using ultraviolet assisted DIW. All polymeric systems show proper viscosity and shear-thinning behavior. The printed model with these inks shows high structural fidelity without any considerable shrinkage in the structure.  DSC data shows good thermal properties for this system, making them good candidates for surgical aid applications.