Thermal Metamaterials with Site‐Specific Thermal Properties Fabricated by 3D Magnetic Printing

Abstract Recently, composites with global anisotropic thermal properties, including thermal conductivity and thermal expansion, have drawn increasing attention as promising thermal‐management materials for highly integrated electrical devices. However, fabricating thermal metamaterials with site‐specific thermal properties remains a great challenge. A 3D magnetic printing process to fabricate fiber‐reinforced composites with site‐specific thermal properties by controlling the orientation of the fibers is presented. In proof‐of‐concept experiments, nickel‐coated carbon fibers (NiCFs) dispersed in resin are site‐specifically aligned according to predesigned patterns through design of the magnet trajectory plan. Composites with aligned fibers are fabricated resulting in site‐specific thermal conductivity that can be locally modulated by a factor of up to 1.39, which is mainly attributable to the aligned NiCFs that can form thermal conductive pathways for phonon transport along the direction of the aligned fibers. These results demonstrate that the thermal properties of composites can be controlled by adjusting the orientation of the fibers. Finally, the present method is applied to fabricate a site‐specific thermal metamaterial as a proof‐of‐concept thermal control. The proposed strategy takes full advantage of 3D‐printing technology, opening a new avenue for manufacturing composites with programmable thermal conductivity, which is thus far inaccessible by traditional manufacturing technologies.