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Advanced functional materials should be developed to address the increasing demand of intelligent systems capable of sensing and self-monitoring. Among different material systems, soft matter composites have attracted much attention during the past several years. Because of their mechanical compliance, they can be used in variety of applications including human computer interactions, wearable biosensors, and internet of things (IoT). Liquid metal polymer composites are a promising class of soft multifunctional materials. Micro and nanoscale droplets of gallium alloys that are liquid at room temperature serve as functional units in these composites. Eutectic gallium indium (EGaIn) and eutectic gallium indium tin (known as Galinstan) are the common non-toxic liquid metal (LM) with high electrical and thermal conductivity. Here, we present a micromechanics model to predict the effective elastic and functional behaviors of EGaInpolymer composites. This Eshelby inclusion-based model has higher accuracy because it accounts for the solid gallium oxide layer that forms around the liquid inclusions. Although the influence of this oxide interphase can be neglected for composites with large diameters (<30 microns), it has a significant effect on elasticity of LM nanocomposites. In addition to studying the core-shell structure of LM inclusions, the formulated model is used for composites with different filler volume fractions and polymer matrices. Moreover, the overall dielectric properties and thermal conductivity of the EGaInpolymer composites are predicted using this model. The modeling results show excellent agreement with finite element analysis and available experimental results. Lastly, we discussed the potential application of LM composites in emerging intelligent systems.
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