Nacre, the iridescent lining of seashells, pairs remarkable strength with remarkable toughness: hard mineral tablets bound by soft organic layers form a "brick-and-mortar" structure that slides and deflects cracks to dissipate energy. Synthetic copies inherit the same trick - and the same flaw. Their soft interfaces work beautifully along the layers, but across them they become easy sites for separation. Keeping that energy-dissipating capacity while making layered composites reliable under loads from every direction has remained an open challenge.
A team led by Professors Huai-Ling Gao and Xiaohao Sun at the University of Science and Technology of China, with Duohong Zou at Shanghai Jiao Tong University, asked a disarmingly simple question: What if the brick-and-mortar architecture were reconfigured into a cylindrical form? In a study published 31 October 2026 in National Science Review, they report a concentric brick-and-mortar architecture in which ceramic platelets wind around the rod axis like the growth rings of a tree.
Rolled into a concentric cylinder, the layers no longer line up in one direction: a crack can no longer find a single straight highway running through the material.
The fabrication is equally pragmatic. Alumina microplatelets bonded by bacterial-cellulose nanofibers self-assemble into flexible films; rolling the films into cylindrical preforms and vacuum-infusing liquid resin, later polymerized in place, yields dense centimeter-scale rods whose concentric layers are the finished microstructure, and no post-assembly shaping is required.
Tested head-to-head against flat brick-and-mortar composites of nearly identical composition and density, the concentric rods came out ahead in every loading mode tried. When they finally failed, cracks were forced along tortuous three-dimensional paths rather than splitting straight along a single plane, so far more energy was consumed in the process. Computer simulations explain why: the concentric layout spreads stress more evenly and never lets long, straight bands of intense shear develop.
The most dramatic gap appeared under cyclic loading. At equal maximum stress in bending, the concentric rods endured more than 1,000 times as many cycles as the flat control. Three-dimensional X-ray images tell the story: damage in the flat material gradually links up into one dominant crack, while in the concentric material the curved interfaces block such connectivity, letting distributed frictional sliding keep dissipating energy for millions of cycles.
As a practical demonstration, the team fabricated a functional drive-shaft prototype and precision structural components directly from the composite, with no secondary shaping of the architecture required. The team is now working to extend the approach to ceramic-based systems and to larger component sizes.
"Rearranging the architecture, rather than changing the ingredients, can remove the globally aligned weak direction of layered composites. We therefore hope to bring nacre-mimetic materials into multi-directional structural applications," Huai-Ling Gao said.
The article, "Concentric brick-and-mortar architecture: beyond planar nacre-mimics", is available online. https://doi.org/10.1093/nsr/nwag681
