A new stereolithographic 3D printing strategy for hydrogels with a large mechanical tunability and self-weldability

3D printing hydrogels with a good resolution, diversified geometries, and a tunable mechanical performance is still a big challenge, which is mainly due to the low photo-reactivity of the high-water containing precursor and the low modulus of the photo-cured hydrogel. In the present work, an acryloylmorpholine - acrylic acid - PEG diacrylate drygel was firstly printed with a good fidelity and subsequently post- treated with an aqueous solution containing specific ions, during which hydration of the hydrophilic network and coordination between the carboxyl and ions occurred simultaneously. The obtained dual-crosslinked hydrogel combined a complex geometry and a good stretchability. This approach decoupled the printability and mechanical properties of the hydrogels. To furtherly show this advantage over conventional direct hydrogel 3D printing, ultrasoft hydrogel lattice structures which cannot be self-supported and purely ionic crosslinked hydrogels with a good self-weldability were demonstrated.