High-performance non-silicone thermal interface materials based on tunable size and polymorphic liquid metal inclusions

Incorporating liquid metal droplets into polymer matrix has become one of the most promising strategies to enhance the thermally conductive performance of thermal interface materials (TIMs) for the escalating heat dissipation demands from highly integrated electronic devices. However, most of the TIMs typically choose silicone polymer as the matrix material, which would exhibit silicone oil precipitation and siloxane evaporation after long time utilization. Here, we present a non-silicone TIM with efficient heat dissipation capability by incorporating multi-shaped and proper-sized liquid metal droplets into an epoxy matrix via a combined fabrication approach. This liquid metal epoxy composite (LMEC) exhibits a high thermal conductivity enhanced up to 14 W \(\hbox {m}^{-1}\) \(\hbox {K}^{-1}\) (nearly 78\(\times\) increase over the matrix) at 85% volume fraction and an ultra-low thermal resistance of 0.0043 K \(\hbox {W}^{-1}\) at 65% volume fraction. Its Kapitza radius and thermal interfacial resistance are estimated from the experimental results, respectively, about 75 nm and \(4.17 \times 10^{-7}\) \(\hbox {m}^{2}\) K \(\hbox {W}^{-1}\), which helps explaining the reduced thermal conductivity of composites with small droplet inclusions. Moreover, actual cooling tests on a high power heating device demonstrate that 65% LMEC shows superior cooling effects than the non-silicone TIMs of indium foil, pure liquid metal, 85% LMEC, and the silicone oil-based liquid metal composites of 65 and 85% volume fraction, which indicate that not the TIMs with higher intrinsic thermal conductivity would exhibit superior heat dissipation effects, but those possessing low thermal resistance between the heat source and heat sink show better heat transfer properties.