Uncovering Aragonite Nanoparticle Self-assembly in Nacre—A Natural Armor

Nacre (mother-of-pearl) has long been identified as the best natural armor, with superior mechanical strength and eminent toughness. How does nacre disperse 95 vol % aragonite nanoparticles in 5% biopolymer matrix without agglomeration? Can we learn from this to produce nacre-like nanocomposites with a high volume fraction of reinforcements? Here we report, for the first time, the direct observation of the aragonite nanoparticle self-assembly process and dome-shaped platelet formation in the nacre from bivalve Perna viridis. At the early stage of platelet formation, the aragonite nanoparticles were found to first self-assemble into a core–shell structure and then form a dome-shaped platelet following the predesigned pattern. The dome-shaped platelets are stacked together to form an interlocking network against sliding of the platelets, thereby contributing significantly to nacre’s strength and toughness. The findings advance our understanding of nacre’s formation mechanism, provide new design guidelines for developing bioinspired materials, and lay a constitutive foundation for modeling the deformation behavior of nacre.