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Fabrication of Layered Gradient Brain-like Tissue by 3D Bioprinting
A B

C

Figure 4. Effect of different pre-cooling time at 4℃ on the performance of the G6A1C1 bio-inks. (A) Curve of viscosity and shear rate
of the mixed bio-inks. (B) Outflow state of the bio-inks. (C) The micro-morphology of the printed structures printed by the bio-inks with
different pre-cooling time.

3.2. Determining the printing parameters of the Table 3. Range and variance analysis data of line width of the
G6A1C1 bio-ink printed structure
Type of data Factor A Factor B Factor C
The G6A1C1 bio-ink was used to print a single- processing
layer grid structure with side length of 12 mm and
spacing of 2 mm. The order of the influence of the Range analysis 730.73 856.53 1213.13
k1
printing parameters on the line width (Table 3) and
forming accuracy (Table 4) of the printed structure k2 761.60 786.60 559.40
was as follows: Needle diameter D > moving speed v k3 811.60 660.80 531.40
653.73
195.73
Range
80.87
> extrusion rate u. Needle diameter D (P < 0.01) and
moving speed v (P <0.05) had significant effects on the Sequence C>B>A B3 C3
Optimal levels
A1
line width. These three factors had no significant effect Optimal combination A1B3C3
on the forming accuracy.
According to the results of these two evaluation Variance analysis 4996.1 29513.9 446455.8
Mean-square value
indexes, the optimal printing parameter for the G6A1C1 F value 5.397 31.883 482.298
bio-ink to print the single-layer structure was chosen
as follows: The diameter D of the needle was 27G, the Significance level ---(0.156) *(0.030) **(0.002)
(P value)
moving speed v was 15 mm/s, and the extrusion rate u was
60 μl/min. When using this printing parameter to print a 3.3. Effect of post-processing on the performance
multi-layer structure, it was found that the extruded inks of the printed structure
could not deposit continuously due to the fast-moving
speed (Figure 5D). Therefore, it was necessary to (1) Effect of temperature on the performance of the
optimize the printing parameters when printing a multi- printed structures
layer structure. The continuity and stability of the printed
multilayer structure can be guaranteed by reducing the G6A1C1 bio-ink was used to print a grid structure with
moving speed (Figure 6). Therefore, according to the 15 layers. The printed structure was immersed into a
experimental results, the printing parameters of multi solution containing 1% CaCl for 30 min at 20°C and
2
layer structure were determined as shown in Table 5. 37°C, respectively. The compression modulus of the
76 International Journal of Bioprinting (2021)–Volume 7, Issue 3