Bioinspired interface engineering through in-situ 3D printing: Achieving process-enabled multifunctional synchronization in high-modulus carbon fiber composites

Next-generation high-power electronics and aerospace systems require structural materials that combine high load-bearing capacity, efficient thermal management, and effective electromagnetic interference (EMI) shielding. High-modulus carbon fiber (HMCF) composites promise these properties, but their 3D printing process faces a key conflict. Low-viscosity resins allow damage-free printing yet create weak interfaces. High-viscosity resins strengthen the interface at the expense of fiber integrity. Here, we report the stable additive manufacturing of continuous HMCF through a bioinspired “rigid-flexible” interface engineering strategy enabled by in-situ 3D printing. A rigid continuous HMCF skeleton is seamlessly integrated with a flexible epoxy/MXene (EPMX) interfacial network. This design protects brittle HMCF during printing while establishing continuous pathways for phonon and electron transport across the interface. The optimized composites deliver record-high performance. Tensile strength reaches 491.94 MPa (111.46% increase), flexural strength is 845.48 MPa (50.36% increase), interlaminar shear strength hits 77.64 MPa (48.08% increase), in-plane thermal conductivity is 42.93 W/(m·K) (99.58% increase), through-plane thermal conductivity is 1.32 W/(m·K) (325.81% increase), and EMI shielding effectiveness reaches 47.95 dB (189.73% increase) via a reflection-dominated mechanism. All these gains come without sacrificing mechanical property. This work establishes a paradigm that converts a manufacturing challenge into a design opportunity, offering a broadly applicable platform for multifunctional composites with synergistic mechanical, thermal, and EMI shielding performance across various fibers and nanomaterial systems.