Tree-inspired bio-composites with 3D anisotropic thermal and electrical conductivities prepared by parallel-engineered graphene integration

Abstract

In nature, numerous bio-materials exhibit anisotropic physical and chemical properties, attributable to their distinctive microstructural characteristics. Inspired by this, artificial composites can be meticulously designed to replicate such anisotropic behavior and attain targeted properties. Here, we successfully constructed wood/graphene bio-composites with parallel-aligned graphene structures by a synergistic process of electrostatic self-assembly and densification using delignified wood as a template. Through the design of parallel-arranged graphene structures, the modulation of phonon and electron transport paths is achieved and differentiated propagation properties are exhibited along different directions. This structural arrangement endows the bio-composites with unique 3D orthogonal anisotropic thermal and electrical conductivity properties. Specifically, the bio-composites integrated with 0.5 wt% graphene demonstrated thermal conductivity of 0.77, 0.25, and 0.12 W/m·K⁻¹ in the x, y, and z directions, respectively, representing a significant enhancement of 2.1–11.8 times over that of natural wood. Concurrently, the electrical conductivity in different directions was markedly improved from 10⁻¹² to 10⁻⁴-10⁰ S/cm. Furthermore, the bio-composites showcased superior tensile strength, reaching up to 79.1 MPa, along with notable flame-retardant properties. In Summary, this research provides a pioneering strategy for the preparation of composites with 3D orthogonal anisotropic thermal and electrical properties, a functionality that enables them to be used for thermal management applications such as thermal insulation and heat dissipation.