Multiscale Interfacial Confined Locking from Nano to Macro Enables Strain Insensitivity in Epidermal Electronic Devices

Stable electrical conductivity in epidermal bioelectronics is essential for accurate health monitoring of humans. Yet, the poor adhesion between active conductive materials and elastic substrate leads to conductivity issues during deformation. Here, a multiscale interfacial confined locking strategy is proposed that combines molecular entanglement between the conductive polymer and the substrate with physical confinement within the electrospun membrane pores. To date, multiscale interfacial confined locking structures show the best interfacial adhesion strength (9.48 MPa) compared to previous works. Such structures benefit from a ≈13.9 times interface adhesion improvement over those without this design. For the first time, multiscale interfacial confined locking structures are prepared by in situ polymerization and swelling to enhance the interfacial adhesion strength, and the method can be extended to different substrates (e.g., polyurethane). The high adhesion promotes the wavy and wrinkled microstructure of the nanomesh film, which enables it to maintain a near-constant resistance under tensile strain (≈200%). The prepared strain-insensitive conductive film has been successfully applied to epidermal bioelectronics (e.g., sensor and bioelectrode).