Bio‐Mimicked Silica Architectures Capture Geometry, Microstructure, and Mechanical Properties of Marine Diatoms

The authors create life‐sized synthetic replicas of marine diatom coscinodiscus sp frustules out of cyclohexyl polyhedral oligomeric silsesquioxanes (POSS). The authors demonstrate that these synthetic structures have biosilica‐like amorphous atomic‐level microstructure and mechanical attributes similar to those of a natural diatom. In situ beam bending and fracture experiments on micron‐sized excised sections of natural and synthetic diatoms reveal similarities in their mechanical properties: a Young's modulus of GPa and a fracture toughness of 0.78 ± 0.10 MPa m^−1/2 for the synthetic materials; those of natural diatoms are GPa and MPa m^−1/2, respectively. In situ single edge notched beam (SENB) bending fracture experiments reveal that fracture behavior of the natural and synthetic specimens is virtually indistinguishable and is characterized by the same brittle failure and crack‐arresting behavior enabled by the double‐wall geometry. Their fracture toughness is comparable to that of fully dense silica, which suggests that the natural diatoms’ frustule maintains its mechanical resilience even at <50% of the weight attained through multi‐scale architecture. The demonstrated ability to fabricate a synthetic hard biomaterial that is virtually indistinguishable from its natural counterpart while capturing its complex architecture, microstructure, and mechanical properties provides a powerful platform for investigating the specific role of each geometrical feature at every relevant length scale in the often sophisticated, multi‐scale hierarchical construct of hard biomaterials, and provides a robust pathway for property optimization.