Soft Hydrogel Shapeability via Supportive Bath Matching in Embedded 3D Printing

Abstract Embedded 3D printing is widely adapted for fabricating architected soft and non‐self‐supporting hydrogels for applications ranging from tissue engineering to soft robotics. Although the matching between hydrogels and supportive baths sets the foundation in embedded 3D printing, the rule‐of‐thumb for supportive bath selection and creation is not yet established. Herein, the “shapeability” of distinct classes of hydrogel inks (i.e., pH‐responsive, photo‐crosslinkable, thermal‐sensitive, chemically crosslinkable monomeric, and cationic and anionic inks) in diverse representative support baths (i.e., gelatin slurry, agarose fluid gel, Carbopol and oil‐based baths) is evaluated. The results show that the dominate mechanisms for interfacial instabilities, including diffusion‐driven or charge‐driven, can be predicted by evaluating the composition pairing of the pre‐crosslinked hydrogel ink and supportive bath. Based on this, a general and simplistic guideline for supportive bath selection to attain hydrogel shapeability is proposed. The approach can widen the spectrum of hydrogel materials that can be structured on‐demand for a plethora of functionalities.