A bottom-up approach to generate isotropic liquid metal network in polymer-enabled 3D thermal management

This work presents a bottom-up approach to construct an isotropic network of liquid metal in polymer, and such generated isotropic liquid metal network brings large enhancement on the thermal and electrical conductivity of the composite for 3D thermal management. The building blocks are composed of polymer particles coated with liquid metal. The liquid metal starts to flow and fill the gaps between the polymer particles, and fuses with each other to assemble into a continuous liquid metal network in the polymer matrix under the mechanical load during heating. The continuous filler network provides effective paths for thermal and electrical conduction, and thus enhances the thermal and electrical conductivity of the composites. Using biphasic copper-eutectic gallium indium as the filler, we generated polymer composites with thermal conductivity as high as 32.71 W/m·K (90 vol%; under compression) and electrical conductivity up to 1.18 × 106 S/m. Moreover, the measurement of the in-plane and cross-plane thermal diffusivity reveals the isotropic enhancement of thermal conductivity in such composites, which may help expand the potential application of these composites in 3D thermal management, flexible electronics, energy conversion and soft robotics.