Bioinspired Chiral Template Guided Mineralization for Biophotonic Structural Materials.

Nature provides numerous biomineral design inspirations for constructing structural materials with desired functionalities. However, large-scale production of damage-tolerant Bouligand structural materials with biologically comparable photonics remains a longstanding challenge. Here, an efficient and scalable artificial molting strategy, based on self-assembly of cellulose nanocrystals and subsequent mineralization of amorphous calcium carbonate, is developed to produce biomimetic materials with an exceptional combination of mechanical and photonic properties that are usually mutually exclusive in synthetic materials. These biomimetic composites exhibit tunable mechanics from "strong and flexible", which exceeds the benchmark of natural chiral materials, to "stiff and hard", which is comparable to natural and synthetic counterparts. Especially, the biomimetic composites possess ultrahigh stiffness of 2 GPa in their fully water-swollen state-a value well beyond hydrated crab exoskeleton, cartilage, tendon, and stiffest synthetic hydrogels, combined with exceptional strength and resilience. Additionally, these composites are distinguished by the tunable chiral structural color and water-triggered switchable photonics that are absent in most artificial mineralized materials, as well as unique hydroplastic properties. This study opens the door for a scalable synthesis of resilient biophotonic structural materials in practical bulk form.