A Flexible and Electrically Conductive Liquid Metal Adhesive for Hybrid Electronic Integration

Electrical and mechanical integration approaches are essential for emerging hybrid electronics that must robustly bond rigid electrical components with flexible circuits and substrates. However, flexible polymeric substrates and circuits cannot withstand the high temperatures used in traditional electronic processing. This constraint requires new strategies to create flexible materials that simultaneously achieve high electrical conductivity, strong adhesion, and processibility at low temperature. Here, an electrically conductive adhesive is introduced that is flexible, electrically conductive (up to 3.25x105 S m-1) without sintering or high temperature post-processing, and strongly adhesive to various materials common to flexible and stretchable circuits (fracture energy 350 <Gc < 700 J m-2). This is achieved through a multiphase soft composite consisting of an elastomeric and adhesive epoxy network with dispersed liquid metal droplets that are bridged by silver flakes, which form a flexible and conductive percolated network. These inks can be processed through masked deposition and direct ink writing at room temperature. This enables soft conductive wiring and robust integration of rigid components onto flexible substrates to create hybrid electronics for emerging applications in soft electronics, soft robotics, and multifunctional systems. This article introduces an electrically conductive adhesive with liquid metal and silver that is flexible, highly electrically conductive, robustly adhesive, and processable at low temperatures. This overcomes several challenges for component integration in hybrid electronic systems and provides a path forward for emerging applications in soft electronics, soft robotics, and multifunctional systems.image