Bio-Inspired Nanonetwork-Structured Materials from Bottom-Up Approach as Mechanical Metamaterials

Nature has long been an outstanding source for inspiring structural designs for fabricating materials with unrivaled mechanical properties, outperforming man-made materials. Inspired by Mantis shrimp, this work aims to suggest a bottom-up approach for the fabrication of well-ordered nanonetwork hydroxyapatite (HAp) thin film using self-assembled polystyrene-block-polydimethylsiloxane (PS-b-PDMS) block copolymer (BCP) with a diamond nanostructure as a template for templated sol-gel reaction. Based on nanoindentation uniaxial micro-compression results, the well-ordered nanonetwork HAp shows high energy dissipation, high energy absorption per volume, and high compression strength, outperforming many cellular materials due to the topologic effect at the nanoscale. Interestingly, similar approach can be applied to mimic the skeleton structure of knobby starfish, providing a bottom-up approach for fabricating nanonetwork-structured single-crystal calcite. The diamond-structured calcite exhibits exceptional specific energy absorption superior to natural materials from a bottom-up approach and artificial counterparts from a top-down approach due to the deliberate structuring at the nanosize. This work highlights the potential of exploiting BCP templated synthesis to fabricate well-ordered nanonetwork monoliths, giving rise to the brittle-to-ductile transition, and thus appealing mechanical properties with the character of mechanical metamaterials.