Interface-Engineered Manufacturing of Gradient Wood with Heterogeneous Structure for Lightweight and Sustainable Structural Materials

Developing sustainable structural materials to replace traditional carbon-intensive structural materials fundamentally reshapes the concept of circular development. Herein, we propose an interface engineering strategy that utilizes water as a liquid medium to replace the residual air within natural wood. This approach minimizes the absorption of water-based softening agents by microcapillary channels of wood, enabling the controlled softening of the cell walls. The resulting spatially heterogeneous structure, induced by surface densification, effectively enhances the mechanical strength of the gradient wood by mitigating strain localization and minimizing damage accumulation. Gradient wood demonstrates a high flexural strength (193.24 ± 12.16 MPa), compressive strength (91.18 ± 2.82 MPa), low density (0.77 g/cm³), and excellent fatigue resistance. Moreover, the dense structure eliminates gaps between wood lumens at the surface of the gradient wood, effectively preventing oxygen infiltration. This gradient wood, characterized by high strength and resistance to combustion, holds significant potential for applications in advanced engineering structures fields.