Page 84 - IJB-9-5

International Journal of Bioprinting Biocompatible BSA-GMA and TPP of 3D hydrogels with free radical type I photoinitiator

Figure 4. SEM images of arbitrary 3D structures of BSA-GMA hydrogels with different contents and degrees of methacrylation processed by TPP. (A) SEM
images of four-pointed star structures of BSA-GMA hydrogels. Scale bar: 5 μm. (B) SEM images of woodpile structures of BSA-GMA hydrogels. Scale bar:
5 μm. (C) SEM images of hollow cage construction of BSA-GMA hydrogels. Scale bar: 1 μm.

Table 3. TPP parameters for 3D structures
Sample Four-pointed star Woodpile structures Hollow cage
R D 52 P = 17.2 mW, V = 110 μm/s P = 15.9 mW, V = 10 μm/s P = 37.0 mW, V = 22 μm/s
20
R D P = 14.2 mW, V = 110 μm/s P = 17.7 mW, V = 10 μm/s P = 11.0 mW, V = 22 μm/s
30 52
R D P = 8.1 mW, V = 110 μm/s P = 13.9 mW, V = 50 μm/s P = 12.9 mW, V = 88 μm/s
40 15
R D P = 6.1 mW, V = 110 μm/s P = 13.9 mW, V = 50 μm/s P = 12.8 mW, V = 22 μm/s
40 35
R D 52 P = 6.0 mW, V = 110 μm/s P = 4.3 mW, V = 10 μm/s P = 5 mW, V = 22 μm/s
40
to the BSA-GMA system. The minimum resolution of the 3D structure of each hydrogel system was obtained by
line width decreases with decreasing concentration and adjusting the processing parameters. We simulated the
methacrylation degree, from 362 nm for R D to 250 nm printing of arbitrary shapes from 2D to complex 3D as
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52
for R D and 199 nm for R D . Figure 3F shows the atomic an example of a two-photon polymerized BSA-GMA
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40
20
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force microscopy (AFM) image of the R D line structure, hydrogel (Figure 4). Table 3 shows the laser processing
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and the line height is 107 nm. The data of the BSA-GMA parameters for the fabrication of 3D structures for each
system are summarized in Figure 3G to thoroughly study hydrogel system. As the concentration and the degree of
the relationship between line width and polymerization methacrylation increased, less laser power was required.
power. The polymerization threshold power decreases with Figure 4A shows the four-pointed star structures that
increasing concentration and degree of methacrylation, illustrate the ability of the BSA-GMA hydrogel to
and the line width increases linearly with increasing power. process sharp patterns with TPP. The BSA-GMA with
The trend is similar for R D , R D , R D , and R D , concentrations of 20 wt% and 30 wt% used high laser
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15
30
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while R D shows an abrupt change, and the line width power, but only a shallow height of hydrogel structure was
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varies more with increasing power. BSA-GMA has better obtained. In contrast, the polymerization power of the three
TPP ability with free radical type I photoinitiator compared samples with different degrees of methacrylation, R D ,
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with pure BSA. The TPP characteristics of BSA-GMA can R D , and R D , decreased with increasing degrees of
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40
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be adjusted according to the degree of methacrylation methacrylation, and the 3D structures were clear without
and the concentration of BSA-GMA, where the degree of significant differences. All five BSA-GMA woodpile
methacrylation has a more obvious effect on the TPP. structures shrunk at a small degree, among which R D ,
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To get the actual accuracy and 3D microstructure R D , and R D had low heights without obvious lays
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15
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capability of this photoresist system in TPP, the optimal (Figure 4B). The woodpile structures of R D and R D
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Volume 9 Issue 5 (2023) 76 https://doi.org/10.18063/ijb.752