Single-Component\nCellulose Acetate Sulfate Hydrogels\nfor Direct Ink Writing 3D Printing

Hydrogels, typically favored for 3D printing due to their\nviscoelasticity,\nare now trending toward ecofriendly alternatives amid growing environmental\nconcerns. In this study, we crafted cellulose-based hydrogels, specifically\nemploying cellulose acetate sulfate (CAS). By keeping the acetyl group\nsubstitution degree (DS<sub>acetyl</sub> = 1.8) and CAS molecular\nweight constant, we varied rheological properties by adjusting sulfate\ngroup substitution (DS<sub>sulfate</sub> = 0.4, 0.7, and 1.0) and\nCAS concentration (2–5 wt %). Rheological characterizations,\nincluding shear-thinning, yield stress, and thixotropy, were performed\nto identify optimal conditions for formulating CAS hydrogel ink in\ndirect ink writing for 3D printing under selected experimental conditions.\nBased on rheological findings, CAS hydrogels with DS<sub>sulfate</sub> 0.7 and concentration of 4 wt % was used for 3D printing, with subsequent\nevaluation of printing metrics. Additionally, the effect of ionic\ncross-linking using Ca<sup>2+</sup> ions on the structural integrity\nof 3D-printed structures was evaluated, demonstrating effective preservation\nthrough reinforced polymer networks. The shrinking and swelling behaviors\nof the 3D-printed structures were also significantly affected by this\nionic cross-linking. Building on these findings, this work could broaden\nthe range of cellulose derivatives available for the preparation of\ncellulose-based hydrogels for 3D printing.