Bionic 3D printed corals

Summary Symbiotic corals have evolved as a highly optimised photon augmentation system leading to space-efficient microalgal growth and photosynthetic quantum efficiencies that approach theoretical limits 1–3 . Corals are characterized by an elastic animal tissue hosting microalgae and a light scattering calcium carbonate skeleton that maximizes light delivery towards otherwise shaded algal-containing tissues 4,5 . Rapid light attenuation due to algal self-shading is a key limiting factor for the upscaling of microalgal cultivation 6,7 . Coral-inspired light management systems could overcome this limitation and facilitate scalable bioenergy and bioproduct generation 8,9 . Here, we developed 3D printed bionic corals capable of growing various types of microalgae with cell densities approaching 10 9 cells mL -1 , up to 100 times greater than in liquid culture. The hybrid photosynthetic biomaterials are produced with a new 3D bioprinting platform which mimics morphological features of living coral tissue and the underlying skeleton with micron resolution, including their optical and mechanical properties. The programmable synthetic microenvironment thus allows for replicating both structural and functional traits of the coral-algal symbiosis. Our work defines a new class of bionic materials capable of interacting with living organisms, that can be exploited for the design of next generation photobioreactors 7 and disruptive approaches for coral reef conservation 10 .