Concentric brick-and-mortar architecture: beyond planar nacre-mimics

The brick‑and‑mortar (BM) architecture of natural nacre is a classic paradigm for biomimetic materials combining strength and toughness. However, conventional planar BM (PBM) architectures exhibit pronounced anisotropy; their direction-dependent weakness compromises structural reliability under complex multi-directional stresses. Here, we introduce a concentric BM (CBM) architecture, with microplatelets circumferentially aligned in a polymer matrix. This design spatially redistributes the weak interlamellar direction axisymmetrically, leaving no globally aligned weak plane and enhancing strength and toughness across multiple loading modes. These gains arise from improved stress homogenization, suppressed interfacial slip and delamination, and energy-dissipative multi-directional crack propagation. Notably, fatigue life under cyclic flexure exceeds that of the PBM counterpart by over three orders of magnitude (>10³-fold) at equal stress. By reconfiguring the PBM motif into a CBM architecture while preserving its strength–toughness synergy, this work provides a biomimetic design strategy for rod-shaped structural components subjected to multi-directional loading.