Liquid metal enables compatible through-plane thermal transport and microwave absorption in flexible PDMS composite

Abstract

Thermal interface materials combining high thermal conductivity with microwave-absorption capability are increasingly required for 5G communication modules, flexible electronics, and aerospace electronic systems, especially as chip sizes shrink and integration density increases. Herein, leveraging the deformability and metallic characteristics of liquid metal (LM) and the high thermal conductivity of boron nitride (BN), we developed flexible polydimethylsiloxane (PDMS)-based thermal interface materials which possess compatible thermal-transport and microwave-absorption performance. The designed composites exhibit tunable thermal-transport and microwave-absorption performance through LM/BN filler regulation. At a total filler loading of 70 wt%, the BN-richer formulation exhibited a measured through-plane thermal conductivity of 1.899 W m −1 K −1 , approximately seven times that of neat PDMS. In contrast, the LM-richer formulation showed stronger microwave-absorption characteristics, with the reflection loss calculated from the measured electromagnetic parameters reaching a minimum of −32.1 dB and a maximum effective absorption bandwidth of 2.16 GHz at a calculated matching thickness of 5.0 mm. These results establish filler partitioning as a practical design parameter for coordinating thermal transport and microwave attenuation in flexible multifunctional thermal interface materials.