Deeply Hierarchical, Multi-Functional Materials from Naturally Grown Biosilica

We grow monocultures of diatoms, single-cellular algae featuring exoskeletons made from biosilica. We harvest these skeletons at gram scales to turn them into macroscopic materials via different routes. For instance, we use 3D-printing to produce structures consisting virtually completely of biosilica, featuring 6 levels of structural hierarchy from the 10-nm to the 10-mm scale. Since diatoms are photosynthetic organisms, this process sequesters carbon and has great potential for a new generation of materials that can remove greenhouse gases during their production. In great contrast to other biologically produced materials, they are inorganic, which gives rise to completely different functionalities. For instance, they can tolerate temperatures of up to 1,000 °C without damage, they show outstanding flame retardance, and they can withstand harsh chemical environments. Since diatom frustules feature outstanding specific strength, our diatom-based materials also have great potential for structural applications. Our preliminary tests have demonstrated specific strengths exceeding that of concrete. Since diatom frustules are highly porous and hollow, our materials can be made to feature densities <0.1 g/cm³, which not only is interesting for lightweight applications, but also leads to low thermal conductivity <0.3 W m⁻¹ K⁻¹. The combination of high temperature resistance and low thermal conductivity makes them excellent materials for thermal management.