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International Journal of Bioprinting Swelling–shrinking behavior of hydrogel

Figure 5. Humidity distribution in the ambient air with a filament diameter of 0.3 mm, illustrating the geometric variation of the printed filament under
various relative humidity (RH) conditions.

concentration of water vapor in the ambient air exceeds As demonstrated in Figure 7B, five geometric variation
that within the hydrogel, moisture absorption occurs at the curves are obtained for the 0.2 mm filament. All curves
fluid–fluid interface, leading to geometric swelling of the display a clear linear reduction over time, with the most
printed filaments. 39 pronounced shrinkage observed at an RH of 50%. Likewise,
The swelling–shrinking behavior of printed filaments the geometric variation curves of the 0.3 mm filament, as
was quantitatively compared and investigated (Figure 7). presented in Figure 7C, show similar trends when the RH
As demonstrated in Figure 7A, the original and deformed is not more than 80%. However, the geometric variation
shapes of the filament are outlined separately using curve exhibits an increasing trend at an RH of 90%.
dashed lines. During the humidity-driven geometric In Figure 7D, linear increases in the curves of 0.4 mm
transforming process, the height of each printed filament filaments occur when the RH is not lower than 70%, with
was measured and symbolized as “H2,” while the height the most prominent swelling occurring at 90% RH.
of the original shape of the filament was symbolized as Generally, significant geometric variations of extruded
“H1,” which corresponded to the radius of the original filaments are not permitted in the manufacturing
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filament. To quantitatively evaluate the extent of geometric of 3D biomimetic architectures. To meet the strict
shrinkage, the ratio of H2 to H1 was calculated for each requirements of medical applications, deviations between
printed filament. the size of the shrinking filament and that of the original

Volume 11 Issue 4 (2025) 417 doi: 10.36922/IJB025220222