Diving-Bell-Spider-Inspired Superhydrophobic Graphene/CNT–Polyurethane Composite for Underwater Strain Sensing

Stable strain sensing in humid and underwater environments requires both controllable electromechanical transduction and protection of conductive pathways against water-induced interference. However, carbon-based flexible sensors often suffer from uncontrolled conductive-pathway disruption during deformation and resistance fluctuation under aqueous conditions. Herein, a diving-bell-spider-inspired superhydrophobic graphene/CNT–polyurethane composite strain sensor (BDBS) with periodic slit structures is developed. The laser-patterned porous PU scaffold localizes deformation around predefined slit regions, thereby regulating the separation and reconnection of conductive pathways. Graphene sheets form extended two-dimensional conductive regions on the porous PU skeleton, whereas one-dimensional CNTs are expected to bridge neighboring graphene-rich domains, helping maintain partial conductive continuity during deformation. Meanwhile, the PDMS-modified rough surface provides a superhydrophobic water-repellent interface that limits direct liquid interference. Through the coupling of slit-guided deformation, conductive-network evolution, and interfacial protection, the BDBS exhibits a gauge factor of 77.09, response/recovery times of 150/175 ms, and stable operation over 10,000 cycles. The sensor further enables human-motion monitoring and differentiation of underwater robotic-shark motion patterns. This work provides a potential bioinspired materials-design strategy that couples mechanically regulated conductive-network evolution with water-repellent interfacial protection for reliable soft sensing in aqueous environments.