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.