Although biomimetic designs are expected to play a key role in exploring future structural materials, facile fabrication of bulk biomimetic materials under ambient conditions remains a major challenge. Here, we describe a mesoscale "assembly-and-mineralization" approach inspired by the natural process in mollusks to fabricate bulk synthetic nacre that highly resembles both the chemical composition and the hierarchical structure of natural nacre. The milfimeter·thick synthetic nacre consists of alternating organic layers and aragonite platelet layers (91 weight percent) and exhibits good ultimate strength and fracture toughness. This predesigned matrix-directed mineralization method represents a rational strategy for the preparation of robust composite materials with hierarchically ordered structures, where various constituents are adaptable, including brittle and heat-labile materials. Biological materials are built from limited components, but their mechanical perfor mances, such as strength and toughness, are far beyond their artificial counterparts. The secret of success is their hierarchically ordered structure at multiscale levels (1 4). The most studied model among these biological rna terials is the nacreous part in some mollusk shells that oonsists of about 95 weight% (wt %) of brittle aragonitic Ca00 3 and 5 wt% of organic materials (5). Mollusks produce nacre by first generating several layers of insoluble 13 chitin matrix filled with silk fibroin gel (6). Then aragonite cores form on the surface of the matrix at the nuclea tion sites (7), followed by lateral growth in the confined space of adjacent organic layers, which finally leads to a V<.ronoi ~ (5). These arago nite platelets, despite their single crystal diffraction pattern, are not perfett single crystals but essen tially cmsist of nanograins with the same aystal lographic orientation (mesocrystals), whereby the platelets are not as fragile as perfect single crys ta1s (8). The mature nacre bas a "brick and mortar" microstructure where aragonite platelet layers are bound by an organic matrix (3). Through a number of such structural designs and toughening mech anisms at muhiscale levels (2, 9, 10), nacre ream ciles its toughness and strength, which are mutually exclusive in most artificial materials (11).In contrast to biological materials, the evolu tion of synthetic structural materials bas been achieved predominately by developing new syn thetic compounds rather than optimizing the micro/nanostructures of existing materials. (Fig. 1, A and B, and fig. Sl), a chitosan matrix with predesigned laminated structure is fubricated ( fig. S2, A, B, D, and E). Then the matrix is acetylated (Fig.lC) and transformed to 13 chitin to avoid unwanted swelling or dissolution ( fig. S2, C and E, and table Sl). The acetylated matrix is mineralized in a peristaltic pump driven circula tory system via the decomposition of Ca(H00 3 )z in the presence of polyacrylic acid (P AA) and M~· (Flg. lD). Then the final material is obtained by silk fibroin infiltration and...

Low-density compressible materials enable various applications but are often hindered by structure-derived fatigue failure, weak elasticity with slow recovery speed and large energy dissipation. Here we demonstrate a carbon material with microstructure-derived super-elasticity and high fatigue resistance achieved by designing a hierarchical lamellar architecture composed of thousands of microscale arches that serve as elastic units. The obtained monolithic carbon material can rebound a steel ball in spring-like fashion with fast recovery speed (∼580 mm s−1), and demonstrates complete recovery and small energy dissipation (∼0.2) in each compress-release cycle, even under 90% strain. Particularly, the material can maintain structural integrity after more than 106 cycles at 20% strain and 2.5 × 105 cycles at 50% strain. This structural material, although constructed using an intrinsically brittle carbon constituent, is simultaneously super-elastic, highly compressible and fatigue resistant to a degree even greater than that of previously reported compressible foams mainly made from more robust constituents.

Energy storage and conversion technologies are considered to be the most promising ways to utilize renewable energy resources. Over the past few years, numerous researchers have dedicated their time to...

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