Yuqin Wang, Li Liu, Masoomeh A. Laskoukalayeh, Nur-Adania Nor-Azman, Nieves Flores, Moonika S. Widjajana, Shih‐Hao Chiu, Sukrit Gaira, Mohamed Kilani, Shi‐Yang Tang, Yanrong Yang, Richard B. Kaner, Mohammad B. Ghasemian, Francois‐Marie Allioux, Kourosh Kalantar‐Zadeh
Liquid metal (LM) polymer composites are made to be soft and deformable but usually require post-synthesis sintering to rupture the insulating gallium oxide shell around droplets to become conductive. Here, we introduce sintering-free Janus composite made of eutectic gallium-indium (EGaIn) dispersed into poly(vinylidene fluoride) matrix, achieving high conductivity (>10 5 S m −1 ) through spontaneous fluorination of the Ga 2 O 3 shell during synthesis. Fluorine doping converts the oxide layer into a highly doped n -type semiconductor, enabling inter-particle electron tunneling. A percolation transition is observed at ∼52 vol % EGaIn, where charge transport shifts from thermal emission near the threshold to field emission at higher loadings. The material's Janus architecture and multifunctionality are demonstrated through motion sensors, bioelectronic interfaces for cellular stimulation, and orientation-dependent thermal management. This reactive-composite strategy recasts the native oxide shell as a tunable semiconductor rather than a barrier, offering a new route to robust, multifunctional soft electronics.