A Bioinspired 3D Tactile Force Sensor under Deep-Sea High Hydrostatic Pressure Environments for Underwater Robotic Adaptive Grasping

Underwater tactile force sensing is crucial for achieving nondestructive and stable object manipulation in ocean robotics, especially in deep-sea environments where traditional vision-based methods are not available due to extreme darkness. However, deep-sea high hydrostatic pressure (>10 MPa) brings in serious interferences on tactile force measurements (<0.01 MPa), leading to few available deep-sea tactile sensors. To solve this problem, this paper develops a biomimetic deep-sea three-dimensional force sensor (3D-DSFS) inspired by the excellent adaptability of deep-sea organisms, where an open lattice sensing layer was developed by flexible 3D printing to balance internal and external pressures of sensors, allowing it to withstand extreme deep-sea hydrostatic pressures. Also, mimicking the hierarchical architecture of human skin, a stratified magnetoelastic sensor was developed for 3D force monitoring. In laboratory pressure-chamber tests, the results demonstrate that the 3D-DSFS is robust to hydrostatic pressures (signals drift <5% within 0-100 MPa) and can reliably detect static and dynamic 3D forces (average error <5%). Integrated into an underwater robotic gripper operating in about 100-m real-world deep-sea environments, the 3D-DSFS can still reliably monitor 3D forces. The 3D-DSFS was used for real-time robotic grasping control, achieving nondestructive and antislippage grasping (unlike sensorless grippers causing damage or slippage). With excellent deep-sea adaptability and accurate 3D force sensing, the 3D-DSFS is anticipated to improve deep-sea robotic operations for ocean engineering fields.