Electrostatically engineered thermal interface materials with multiscale boron nitride-alumina-nanodiamond fillers in polyvinyl alcohol composites for tailored anisotropic thermal conductivities

Thermal interface materials (TIMs) are essential for managing heat in high-power electronic devices, yet developing advanced TIMs faces challenges due to interfacial thermal resistance between fillers or at filler-matrix boundaries. Furthermore, the anisotropic nature of micro-nanostructured fillers like 1D/2D materials limits the optimal tuning of in-plane and through-plane thermal conductivities. Herein, we introduce electrostatically engineered TIMs using multiscale hybrid fillers—modified boron nitride (m-BN)-alumina (Al₂O₃), and m-BN-nanodiamond (ND)—dispersed in polyvinyl alcohol (PVA) to manipulate m-BN alignment and reduce interfacial resistance, tailoring anisotropic thermal conductivities. In the multiscale design, m-BN layers (~ 100 nm) surround spherical Al₂O₃ particles (microscale) to disrupt planar alignment, while ND particles (5–10 nm) bridge gaps, enhancing alignment and interfacial contact. The optimal TIMs achieve a 54% reduction in anisotropy index and a 192% improvement in through-plane thermal conductivity compared to m-BN-only TIMs. The composites exhibit a 37% increase in strength and a 234% improvement in elongation, alongside low dielectric constant and loss factor, fulfilling multifunctional requirements such as mechanical integrity and electrical insulation. LED cooling components using the TIMs lower operating temperatures, confirming their outstanding performance. This hybrid design offers a versatile framework for multifunctional TIMs, extending to other 2D materials like graphene, MXene, and metal dichalcogenides. Electrostatically engineered thermal interface materials (TIMs) using multiscale hybrid fillers—modified boron nitride (m-BN), alumina (Al₂O₃), and nanodiamond (ND)—dispersed in polyvinyl alcohol (PVA) composites are devised to tailor the desired anisotropic thermal conductivities. The optimal TIMs achieve a 54% reduction in anisotropy index and a 192% improvement in through-plane thermal conductivity compared to m-BN-only TIMs. The composites exhibit a 37% increase in strength and 234% improvement in elongation, alongside low dielectric constant and loss factor, fulfilling multifunctional requirements such as mechanical integrity and electrical insulation.