Diffusion-induced phase separation 3D printed scaffolds for dynamic tissue repair

Many hydrogen-bonded cross-linked hydrogels possess unique properties, but their limited processability hinders their potential applications. By incorporating a hydrogen bond dissociator (HBD) into these hydrogels, we developed injectable 3D printing inks termed diffusion-induced phase separation (DIPS) 3D printing inks. Upon extrusion into water and subsequent diffusion of HBD, these ink cure rapidly. The DIPS-printed scaffold retained most of the original hydrogel properties due to the regeneration of hydrogen bonds. Additionally, the reversible nature of hydrogen bonds provides DIPS 3D-printed scaffolds with exceptional recycling and reprinting capabilities, resulting in a reduction in the waste of valuable raw ink materials or additives. Postprocessing introduces new crosslinking methods that modulate the mechanical properties and degradation characteristics of DIPS scaffolds over a broad range. Based on its suitable mechanical properties and bioactivity, we successfully repaired and functionally reconstructed a complex defect in penile erectile tissue using the DIPS scaffold in a rabbit model. In summary, this approach is relevant for various hydrogen-bonded cross-linked hydrogels that offer mild printing conditions and enable the incorporation of bioactive agents. They can be used as scaffolds for dynamic tissue reconstruction, wearable devices, or soft robots.