The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smtd.202200246.The inorganic particle can react with the liquid metal by the mechanically induced reaction; b) The inorganic particle cannot react with the liquid metal by the mechanically induced reaction. The melting point of Ga, eGaIn, Galinstan, In, In-Bi, and Pb-Bi is respectively 29.8, 15.4, 6, 156.6, 72, and 125 °C. And they were ground with the inorganic particle at temperatures above their melting point.

For advanced thermal interface materials (TIMs), massive inorganic addition for high isotropic thermal conductivities conflicts with suitable rheological viscosity for low contact thermal resistance. Traditional strategies rarely resolve such a contradiction, and it remains an academic and industrial challenge. Herein, inspired by the structure and function of the bone joint, a best-of-both-worlds approach is reported that endows a standard polydimethylsiloxane/alumina (PDMS/Al 2 O 3 ) TIM with simultaneously enhanced rheological mobility and thermal conductivity. It is conducted by employing morphology-controllable gallium-based liquid metal (LM) to the surface of Al 2 O 3 by a scalable mechanochemical process. At the typical polymer-LM-Al 2 O 3 interface, LM droplets with low cohesive energy can release the freedom for macromolecular chain relaxation and reduce the viscosity, successfully allowing the high-loading TIMs (79 vol.%) to keep the thixotropic state and effectively reducing its contact thermal resistance with a copper substrate by 65%. At the same time, adjacent LMs merge to thermally bridge separate Al 2 O 3 particles, which facilitates the interfacial thermal conduction and enhances the thermal conductivity from 5.9 to 6.7 W m −1 K −1 . Along with additional electrical insulation, this filler modification strategy is believed to inspire others to develop high-performance polymer-based TIMs for future advanced electronics.

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