Double-Sided Mechanical Interlocking Enables Soft-Rigid Conductive Interfaces With a Record High Toughness for Flexible Electronics

The pronounced mismatch between polymeric electrodes and metallic components hinders the formation of robust electrical contacts. While most approaches rely on chemical design to strengthen interfacial interactions, we present a double-sided mechanical interlocking strategy that provides both stability and adaptability. A conductive fabric scaffold bridges polymers and metals, with adhesives sequentially applied to both sides. The adhesive infiltrates and encapsulates scaffold fibers, forming a thread–hole adhesion that can only be disrupted by bulk failure. This mechanism achieves a record high interfacial toughness of 730 J m⁻² between conductive elastomer and copper using commercial silver pastes. Peeling tests show delamination occurs between silver paste and copper, indicating even higher toughness could be obtained with better-performing products of conductive adhesive. Notably, the interface stability surpasses that of the electrode itself, remaining intact even when the electrode fails. The design is broadly compatible with elastomeric or hydrogel matrices and with diverse commercial adhesives. It enables the construction of reliable epidermal electronics and hydrogel-based devices. Overall, this interlocking strategy provides a versatile platform for integrating soft and rigid conductors in hybrid electronic systems.