Enhancement of In-Plane Thermal Conductivity of Flexible Boron Nitride Heat Spreaders by Micro/nanovoid Filling Using Deformable Liquid Metal Nanoparticles

With the fast development of integrated circuit devices as well as batteries with high energy densities, the thermal management of electronic components is becoming increasingly crucial to maintaining their reliable operations. Boron nitride nanosheets (BNNS), which have superhigh thermal conductivity along the in-plane direction while remaining electrically insulating, were widely regarded as an ideal filler for preparing high-performance polymer composites to address the “thermal failure” issue. However, due to the instinctive rigidity of BNNS, the nanosheets are unable to form a tightly interfacial contact between the adjoining fillers, resulting in some micro- and nanovoids within the heat transfer pathways and severely limiting further thermal conductivity enhancement for BNNS-based composites. Herein, soft and deformable liquid metal (eutectic gallium-indium, EGaIn) nanoparticles were employed to fill the gaps between the adjacent BNNS with a rational design of mass ratios of BNNS and EGaIn, leading to a strongly synergistic effect with BNNS on thermal conductivity improvement. As a result, the composite film (BNNS: 63 wt