Page 294 - IJB-9-2

International Journal of Bioprinting Methodology of hydrogel printability

Figure 5. Platform designed to carry out the collapse test of the hydrogel
filaments extruded with bioprinter.

Thus, printability (Pr) is defined by the following
[24]
equation :
π 1 L 2
Pr = • = (II) Figure 6. Visualization of a hydrogel with low gelation (A), with perfect
4 C 16 A gelation (B), and with excessive gelation (C).
Where C (circularity) is:
Table 4. Characterization of the printability of HAMA 5%
4π A
C = (III) using the quantitative assessment of gelation state
L 2
Hydrogel Image Pr State of
Where L is perimeter and A is area. gelation
Pr = 1 implies the square printing shape of the holes in HAMA 5% <1 Low
the matrix and thus presents a perfect gelation condition .
[25]
Thus, the closer the value obtained is to 1, the higher the
printability of the hydrogel. On the other hand, a hydrogel
that obtains a printability value lower than 1 will exhibit
low gelation, and a hydrogel that obtains a value above 1
will exhibit excessive gelation (Figure 6).
The data can be used to study the gelation properties of In the following example (Table 4), the printability
the same hydrogel when the concentrations of the different of HAMA 5% was observed. According to the scheme
elements that form it are modified, or even to compare presented above in Figure 6, and depending on the
different types of hydrogels according to these properties amorphous shape of the squares in the matrix, the value of
in order to determine which one has better printing Pr is lower than 1 (Pr < 1), indicating that the printability
characteristics. is poor.
The images to observe the Pr value are obtained using a 3.4. Printing grid test
USB 40× to 100× digital microscope placed perpendicularly Printing grid test allows to determine the capacity of a
to the surface where the regular matrix is located, which, hydrogel to reproduce a given pattern and its tendency
as already mentioned, allows sharp images to be captured to generate accumulations or clusters . It can be used to
[26]
and processed directly on the computer. The platform check whether the hydrogels under study have sufficient
used to support the microscope and allow the images to be mechanical properties to generate a grid or pattern of
obtained from the same position and angle was designed squares and rectangles of different dimensions like the one
with Inventor. in Figure 7.

Volume 9 Issue 2 (2023) 286 https://doi.org/10.18063/ijb.v9i2.667