Machine Learning Enabled Fluorescent Anti-Freezing Core-Shell Hydrogel Realizing Deep-Sea Morse Code Communication for Human-Machine Interaction Engineering.

Underwater intelligent systems demand flexible materials with robustness, environmental tolerance, and functional integration. Hydrogels, which combine flexibility with conductivity, show promise but often fail under harsh conditions. Herein, an antifreezing, antiswelling hydrogel with core-shell architecture was fabricated by ion concentration gradient modulation. Polyacrylamide/poly(acrylic acid) pregel immersed in Al3+ solution produced a concentration gradient. The external layer generates a dense metal oxide film, acting as a robust protective armor, while the inner polymer network preserves elasticity. A dynamic cross-linking network endowed the hydrogel with mechanical robustness (561% strain) and fracture strength (0.188 MPa stress), superior frost resistance (-48 °C), and a swift response time (198 ms). Machine learning-enabled Morse code decoding established a nonverbal underwater communication system, enabling remote human-machine interaction and efficient robotic control. The proposed hydrogel-based system achieves integrated "sensing-control-communication" in extreme environments, offering innovative strategies for continuous digital motion monitoring and human-machine interaction.