In-situ printing of an oxygen-generating tubular alginate hydrogel embedding Chlorella vulgaris

Immobilizing microalgae in hydrogels offers advantages over suspension culture, allowing for a compact design of a photosynthetic system in air. Despite the bioactivity of microalgae embedded in a hydrogel, a continuous supply of water and nutrients is crucial to sustain photosynthesis for extended periods. A tubular structure of an alginate (ALG) hydrogel can be formed using matrix-assisted three-dimensional printing encapsulating Chlorella vulgaris through ion crosslinking. A silicon-nanoparticle matrix with multivalent cations enables spontaneous solidification of ALG liquid inks with high-fidelity printing, creating optimal printing and ion-diffusion parameters for the fabrication of tubular hydrogel structures. The bioactivity of C. vulgaris in hydrogels is confirmed by measuring the level of generated oxygen about 13 mg/L at 0.1 mL/min of flow rate through the tubular hydrogel structures, and the generation efficiency supports the application of microalgae in purification in the future.