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International Journal of Bioprinting Swelling–shrinking behavior of hydrogel

under optimal RH conditions of 90, 80, and 60%. Under the mechanical or biological properties required for
these conditions, the constructs maintained splendid shape medical applications.
throughout the 3D printing process. The well-arranged The observed phenomena can be explained as follows.
F-127 filaments provided stable support for adjacent
layers and exhibited smooth, uniform shapes. In contrast, The medical-grade biodegradable hydrogel used in this
Figure 9D–F presents ear models printed under study consists of hydrophilic polymer networks that retain
inappropriate ambient RH conditions of 80, 70, and 50% for plenty of water and exhibit pronounced humidity-driven
the small, medium, and large sizes, respectively. Although swelling–shrinking behavior. As illustrated in Figure 6,
the F-127 hydrogel filaments initially appeared continuous to minimize moisture loss and geometric variation of the
upon deposition, as printing proceeded, a gradual hydrogel filaments, specific RH levels were selected as
shrinkage and even collapse occurred due to inappropriate the optimal RH for each filament diameter. Since the ear
ambient RH. This compromised the capability to support models (Figure 9A–C) were printed under these selected
the upper layers and resulted in irregular holes within the RH conditions, the shape of each hydrogel filament was
3D-printed architectures. At the edges of each model, an maintained throughout the manufacturing process. On
evident moisture loss occurred, as demonstrated in the the contrary, when the ambient RH was inappropriate
micrographs. These fragile structures often fail to provide (Figure 9D–F), the moisture loss led to geometric shrinkage.

Figure 9. Photographs and micrographs of the 3D-printed ear models. (A–C) Ear models printed with filament diameters of (A) 0.2 mm, (B) 0.3 mm,
and (C) 0.4 mm under optimal ambient humidity conditions. (D–F) Corresponding models printed under relatively low ambient humidity conditions,
showing structural deformation. Scale bar for all upper panels: 10 mm; Magnification: 8×. Scale bar for all lower panels: 0.5 mm; Magnification: 64×.

Volume 11 Issue 4 (2025) 421 doi: 10.36922/IJB025220222