A Biomimetic Thermal Conduction Network Enables Metal-Level Thermal Conductivity in Polymer Nanocomposites

The rapid miniaturization and integration of modern electronics have intensified heat generation, creating an urgent demand for high-performance thermal interfacial materials (TIMs). Although constructing oriented thermal conduction networks in polymer composites is effective in achieving high through-plane thermal conductivity for TIM applications, conventional approaches often involve harsh processing and overlook limitations in the overall heat flux, hindering further breakthroughs in thermal conduction performances. Herein, inspired by the transpiration process in bamboo, we design a biomimetic "bamboo stem array-leaf" thermal conduction network using a mild noncovalent functionalization and hierarchical structural assembly strategy. In this design, vertically aligned polydopamine-functionalized pitch-based carbon fibers (mPCFs) act as "stems" for primary heat conduction, while polyamide epichlorohydrin-modified graphene nanoplatelets self-assemble onto the mPCFs, serving as "leaves" to enhance horizontal heat diffusion. This bioinspired network synergistically integrates efficient long-range heat transport with enhanced interfacial thermal coupling with the polymer matrix, boosting the overall heat flux across the composite. The resultant epoxy composite achieves an exceptional through-plane thermal conductivity of 289.5 W m^-1 K^-1, surpassing most polymer composites and even certain metals. Moreover, the underlying thermal conduction mechanisms are clarified by correlating experimental results with predictions from classical models and finite element simulations. This work establishes an alternative paradigm for developing high-performance polymer nanocomposites with metal-like thermal conductivity for advanced TIM applications.