Starch granular hydrogels with enhanced mechanical properties and 3D printing performance: Fabrication and characterization.

Traditional bulk starch hydrogels have weak mechanical properties and poor printability. In this study, ethanol-annealed potato starch was used to construct starch granular hydrogels (12-20% w/v). At 15%, the starch granular hydrogel (SGH15) exhibited significantly higher hardness (1390.52 g vs. 245.28 g), storage modulus (5202.90 Pa vs. 107.19 Pa), and relative crystallinity (13.0% vs. 10.9%) than traditional potato starch hydrogel (PSH15). Cryo-SEM revealed that, unlike traditional bulk hydrogel networks, the starch granular hydrogel consists of densely packed swollen starch granules with pore sizes ranging from 0.02 to 0.88 μm, which are smaller than those of PSH15 (0.77-3.12 μm). With increasing concentration from 12% to 20%, the granular hydrogels exhibited progressively higher hardness, modulus, and crystallinity, while the pore size decreased. All granular hydrogels exhibited strong gel behavior (tan δ < 0.1), unlike PSH15 (tan δ > 0.1). Notably, SGH12 and SGH15 (12% and 15% granular hydrogels) exhibited favorable thixotropic recovery and printability, forming stable 3D structures, whereas PSH15 collapsed. This study developed starch granular hydrogels in which swollen starch granules act as structural units to reinforce the hydrogel network, providing a novel approach to designing starch-based materials with enhanced mechanical properties and superior 3D printing performance.