This graduation report aimed to improve the mechanical properties of a sustainable 3D print material made of microalgae, in order to create an macro-porous 3D structure with enhanced longevity and photosynthetic activity. This research builds upon the alginate based bio-ink from Balasubramanian et al (2021). Their material proposal lacked structural stability and print resolution, which made geometries of more than six layers impossible. Moreover, the bioprints were confined to a nutrient plate. These challenges formed the motivation for the research. The goal for the optimized bioprinting protocol was to make use of the advantages of additive manufacturing, by creating a macro-porous shape with increased surface ratio. The hypothesis was that the microalgae would have more access to light, air and nutrients which would increase oxygen release and carbon dioxide fixation. In a series of explorative studies, in close collaboration with nanobiologists, biomaterial designers and 3D printing experts, a direct ink writing approach was selected to construct the microalgae bioprints. Additional components were added to the alginate bio-ink formulation, which concluded in a material with improved print fidelity and resolution, so that more than 25 layers could be bioprinted. With the optimized protocol, the 3D printed construct could be crosslinked so that the print was stable enough to be handled. The microalgae immobilized in the ink formulation survived more than seven days in the 3D printed geometry. The photosynthetic performance of the material was observed, by building an incubator prototype with oxygen and carbon dioxide sensors. The sensors measured two different bioprints simultaneously, a macro-porous cube and a solid cube. The superiority of the photosynthetic ability of the porous geometry over the solid geometry could not be concluded, due to the limitations of the sensors and the prototype setup. Important insights were found for further research on the improvement of the test setup. The optimized microalgae bio-ink is a valuable material with sustainable benefits. The material can actively fight carbon dioxide pollution, is carbon neutral in production and is biodegradable. The technical optimization of the bio-ink in this study formed the first steps towards a functional living microalgae artefact.