The rapid development of integrated electronic devices towards miniaturization and high-power density brings to great challenge of thermal management to guarantee the lifespan and reliability of electronic devices. However, efficient heat dissipation in electronic systems is currently limited by the thermal conductivity and capability to direct heat toward heat sinks that achieved by thermal interface materials (TIMs).[1] Hexagonal boron nitride (BN) is a promising 2D material for making thermal interface materials in electronic systems thanks to its electrically insulation, high thermal conductivity, and chemical inertness.[2] The emergence of 2D material with remarkable performances in microscopic scale provides great potential to enhance functionalities in macroscopic devices. Recent experimental efforts to control the local orientation of 2D material have demonstrated significant advances in improving the bulk material performances.[3]

Herein, we create the high thermal conductivity BN-based composites as thermal interface materials by locally orienting the functionalized BN platelets using magnetically assisted slip casting.[4] The intrinsic alignment of BN composites can be precisely and remotely controlled by an external magnetic field, so that the heat can be intentionally directed to specific areas along alignment direction and promptly dissipated out of the system. As expected, the composite with vertically assembled BN platelets achieves unusually high thermal conductivity of 12.1 W/mK along the direction of alignment and good thermal stability up to 120 °C. In addition, the locally graded BN orientations in the proof-of-concept composite enable directed heat transfer away from two vertically stacked heat sources, demonstrating the potential of efficient thermal management in 3D integrated electronics.