Reverse biomimetic interface protection inspired by fish scale structure for high-performance optimization of rice straw/magnesium oxychloride composite materials

This study aimed to address the technical challenges associated with the practical application of magnesium oxychloride cement (MOC), such as its poor interfacial compatibility and limited water resistance. This study, adopting a non-conventional conceptual framework, inspired by the structural characteristics of fish scales employed the reverse biological design approach and, for the first time, successfully achieved the bonding and reorganization mechanism of trisodium citrate (TC) within the rice straw/MOC composite material (RS/MOC), an internal microstructure that was inversely aligned and organized compared with the directional arrangement of fish scales was formed. This structure effectively resisted the directional drainage effect and impeded water penetration. The influence of TC surface modification on the water resistance and mechanical properties of RS/MOC was systematically examined. The fabricated inverse bionic composite material achieved an average density of approximately 0.23 g/cm³ . The results showed that a TC content of 0.15 % yielded the optimal overall performance. The flexural strength and compressive strength of the composite material were 1.25 MPa and 3.3 MPa, respectively, and its water resistance was significantly improved by 180 %. Furthermore, the naturally low thermal conductivity of rice straw and the porous architecture of the composite endowed the material with excellent thermal insulation properties. This research provides insight into the high-value utilization of agricultural waste and proposes an innovative, environmentally sustainable pathway for developing lightweight building materials. • Achieved high added value and high utilization rate of rice straw. • Reverse-bionic application of fish-scale structure's efficient drainage effect in cement materials for the first time. • Fabricated high-strength, water-resistant green lightweight composites.