2.6. Process parameters and microstructure
Understanding of the shear stress is a crucial factor to consider in the 3D bioprinting process. Studies have demonstrated that shear stress is affected by the diameter of the nozzle, printing pressure, and viscosity of the material to be printed. However, in mechanically driven extrusion-based printing, extrusion speed is another important factor that affects shear stress. When the nozzle diameter and hydrogel viscosity remain unchanged, the shear stress increases with the extrusion printing speed.
We examined the microstructure of hydrogel filament by 3D printing with varied extrusion printing speed and nozzle diameter to freeze the cross-sectional structure formed during extrusion. Then, according to the shear stress gradient at the nozzle, we established a model diagram for pore distribution of the printed gel fibre section.
2.7. Microstructure of samples
After immunofluorescence, the cells on the material were fixed. Next, the samples were washed with phosphate-buffered solution (PBS), dehydrated stepwise with a graded series of ethanol (50, 70, 90, and 100% v/v), and sputter-coated with gold (~20 nm). The samples were examined at an acceleration of 15 KV by using a scanning electron microscope.