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Silver-Coated Poly(dimethylsiloxane) Beads for Soft, Stretchable, and Thermally Stable Conductive Elastomer Composites

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journal contribution
posted on 02.11.2019, 18:29 by Chengfeng Pan, Yunsik Ohm, Jingxian Wang, Michael J. Ford, Kitty Kumar, Swarun Kumar, Carmel Majidi
We introduce an elastomer composite filled with silver (Ag) flakes and Ag-coated poly­(dimethylsiloxane) (PDMS) beads that exhibits electrical conductivity that is 2 orders of magnitude greater than that of elastomers in which the same concentration of Ag filler is uniformly dispersed. In addition to the dramatic enhancement in conductivity, these composites exhibit high mechanical compliance (strain limit, >100%) and robust thermal stability (conductivity change, <10% at 150 °C). The incorporation of Ag-coated PDMS beads introduces an effective phase segregation in which Ag flakes are confined to the “grain boundaries” between the embedded beads. This morphological control aids in the percolation of the Ag flakes and the formation of conductive bridges between neighboring Ag shells. The confinement of Ag flakes also suppresses thermal expansion and changes in electrical conductivity of the percolating networks when the composite is heated. We demonstrate potential applications of thermally stable elastic conductors in wearable devices and soft robotics by fabricating a highly stretchable antenna for a “smart” furnace glove and a strain sensor for soft gripper operation in hot water.