Bioinspired Integrated Auxetic Conductive Elastomer Composite With High Stretchability and Robust Interface.

Auxetic conductive elastomers (ACEs) are appealing due to their unique negative Poisson's ratio (NPR) effects. Nevertheless, conventional ACEs are often produced by the creation of geometric structures through pore-forming techniques on conductive elastomers, which substantially compromise their mechanical and conductive performance. Inspired by the composite structure of skin comprising collagen fibers and elastin, this study reports an integrated auxetic conductive elastomer (IACE) composite composing a high-modulus conductive elastomer as the auxetic skeleton and a low-modulus conductive elastomer as the soft matrix. Benefitting from the covalent interlinkages and topological entanglements at the skeleton-matrix interface, the IACE is flat and void-free with no abrupt soft-to-hard transition. Compared to the auxetic skeleton alone, the IACE exhibits enhanced mechanical properties, including a fracture stress of 2.6 MPa, an elongation at break of 457%, and a toughness of 7.2 MJ m-3. Furthermore, its auxetic behavior with NPR effect is consistently observed across a wide strain range of 0-85%. Leveraging the unique ion transport pathway enabled by auxetic deformation, the IACE demonstrates reliable sensing performance with improved sensitivity over a broad deformation range. This work presents a promising strategy for developing ACEs with the robust interface and wide auxetic strain, advancing their potentials in intelligent flexible electronics.