Bioinspired Zwitterionic Hydrogels With Bound‐Water Reinforcement for Deep‐Sea Robotic Velocity Sensing

ABSTRACT Mechanosensing plays a critical role in enabling precise underwater vehicle navigation and trajectory estimation; however, challenges persist in device robustness and signal fidelity under high hydrostatic pressure. Inspired by the pressure‐adaptation strategy of deep‐sea organisms, we developed a zwitterion‐modified triple‐network hydrogel featuring poly(vinyl alcohol)/poly(acrylamide) backbones and trimethylamine N‐oxide (TMAO)‐derived ion pairs. In this hierarchical architecture, pTMAO acts as a cooperative factor that modulates the local hydration environment, thereby facilitating the subsequent formation of densely packed crystalline domains through zwitterion‐amplified Hofmeister crosslinks. This mechanism stabilizes hydration shells and preserves Grotthuss proton‐relay efficiency, enabling 26.9 MPa compressive strength and 96.7% signal retention under laboratory‐simulated kilometric hydrostatic pressure. Integrated with a vortex‐induced vibration sensor and a physics‐informed neural network, the system achieves underwater trajectory reconstruction with only 1.8% error. Furthermore, shallow‐water insitu trials in the Bohai Sea demonstrate a mean descent velocity estimation error of 3.62 mm s − 1 without rigid housings. These results establish a biomimetic design strategy for pressure‐resistant soft materials and demonstrate a hydrogel‐based mechanoelectrical sensing platform validated in real ocean environments, paving the way for future deep‐sea exploration.