Hetero-structured hydrogel with transition layer: Achieving synergistic sensing-actuating integration for intelligent ship

Temperature-driven hydrogel actuators exhibit great potential due to their stimulus responsiveness property, flexible design, and low energy consumption. However, the asymmetry of the conventional bilayer hydrogel makes the structure with low interfacial toughness and more prone to delamination. Herein, the polyacrylamide-polydopamine/photo-initiated-poly (N-isopropylacrylamide)‑sodium alginate-CaCl 2 (PPM/ p -PM-Alg-Ca 2+ ), a hetero-structured bilayer hydrogel featuring a transition layer, was developed. Due to the good water absorption of the p -PM-Alg-Ca 2+ layer, the pre-solution of the PPM penetrated into the p -PM-Alg-Ca 2+ layer and formed interpenetrating networks to achieve topological entanglement at the interface, obtaining a bilayer hydrogel with a transition layer. The bilayer hydrogel demonstrates the performance of rapid response actuation (30 s bending from 0° to 320°) and recovery capability (40 s restoring to original state), good signal conversion ability and fast response time (40 ms), and good photothermal performance (heated to 66 °C within 7 min under 808 nm laser irradiation). The transition layer enhanced the interfacial toughness (17.0 kPa) to inhibit the separation of bilayer structure. The hydrogel integrates into the sensor and actuator to realize the non-contact security alarm, dynamic monitor of a ship, and actuator for item collection, providing an integrated solution for the intelligent upgrading of ships and effectively supporting the construction of an intelligent system.