New high thermal conductivity materials have been developed to enable enhanced heat transport within electronics packages and other thermal management applications. Many of these engineered materials have anisotropic thermal properties inherent to their fabrication, especially the sheet-like materials that are commonly used as heat spreaders. [1] For example, large-area graphene/graphite sheets fabricated in roll-to-roll processes have high in-plane thermal conductivity (but lower through-thickness conductivity)[2] and reinforced polymer composites that include high-strength carbon fibers have high thermal conductivity along the axis of the fibers, but poorer thermal conductivity in the direction perpendicular to the fibers.[3] Generally, these materials offer significantly improved hot spot dissipation compared to conventional heat spreaders, but their anisotropic properties must be characterized to allow for accurate design of thermal solutions.