Thermal conductivity and mechanical durability of graphene composite films containing polymer-filled connected multilayer graphene patterns

Due to its high thermal conductivity, graphene has received much attention as a thermal interface material (TIM) for dissipating heat, which would otherwise be accumulated in heat sources, to heatsinks. However, the weak interlayer force induces tearing of graphene under repeated deformation; hence, the application of graphene as a TIM in the manufacturing of flexible electronics has been limited. To overcome this hurdle, the graphene composite (GC) films, in which thermoplastic polymers were infiltrated into connected multilayer graphene (MLG) patterns, were fabricated in this study. While the connected MLG patterns attained high in-plane thermal conductivity (κ_x), the polymers prevented tearing of the graphene. To investigate the effect of the graphene content on the κ_x of the GC films, the area of MLG patterns was carefully adjusted by coating a graphene solution through metal masks with various opening sizes. The κ_x of the GC-4 film was calculated as 53 W/m·K, which was slightly changed after 10,000 folding test cycles with a 1.5-mm bending radius.