Through-Thickness Vertically Aligned Graphene-Fiber Thermal Interface Materials with Thermal Conductivity Approaching the Parallel-Model Estimate and Low Thermal Contact Resistance.

Conventional elastomer-based thermal interface materials (E-TIMs) are constrained by the trade-off between high thermal conductivity and low thermal contact resistance, limiting their use in high-power chip cooling. We developed a vitrimer-enabled, through-thickness vertically aligned graphene-fiber E-TIM that addresses this limitation by combining vertically continuous heat-conduction pathways with an adaptive polymer interface. Continuous graphene fibers were mechanically aligned, infiltrated with a β-hydroxy ester vitrimer-based polydimethylsiloxane matrix, and assembled through stacking-welding to form dense, continuous heat-transport pathways along the thickness direction. At a graphene-fiber volume fraction of only 16.71 vol %, the E-TIM achieves an ultrahigh through-plane thermal conductivity of 160.2 W m-1 K-1, approaching the parallel-model estimate, indicating efficient translation of the axial thermal conductivity of GFs into macroscopic through-plane heat transport. Thermally activated transesterification in the vitrimer matrix enables stress relaxation, layer welding, and interfacial morphological reconstruction, reducing the thermal contact resistance to 14.4 mm2 K W-1 under 40 psi. Molecular dynamics simulations further suggest that vitrimer-induced interfacial reconstruction increases the effective contact area and interfacial thermal conductance beyond conventional viscoelastic creep. In a device-level cooling demonstration, the E-TIM outperforms a commercial E-TIM by lowering the steady-state heat-source temperature by 20.8 °C, highlighting its strong potential for high-power chip thermal management.