A Function‐Structure‐Integrated Optical Fingertip with Rigid‐Soft Coupling Enabling Self‐Decoupled Multimodal Underwater Sensing

ABSTRACT Achieving reliable underwater force‐feedback grasping and sensing remains a grand challenge due to system fragmentation, spatiotemporal desynchronization, and poor stability in aquatic environments. Here, we report a function–structure–integrated optical fingertip sensor that synergistically combines multimodal perception with a rigid–soft hybrid bionic design. Embedded distributed fiber Bragg gratings (FBGs) and a structurally decoupled architecture enable simultaneous sensing of contact force (60 ms response), slip, temperature (7.53 pm/ C), and underwater pressure (2.57 pm/kPa). Functional partitioning of the flexible skin, skeletal frame, and internal diaphragm allows unified contact, state, and environmental perception within a centimeter‐scale device. A bioinspired protruding interface amplifies local strain while effectively decoupling normal and tangential forces. In addition, the sensor demonstrates outstanding electromagnetic‐interference immunity, long‐term operational reliability, and robust underwater sealing, enabling stable performance in complex aquatic environments. Experiments show high classification accuracy (97.9% hardness; 100% roughness) and excellent pressure‐sensing linearity . We additionally developed a cable‐driven dual‐finger underwater system enabling synchronous multimodal monitoring and adaptive stable grasping under buoyancy‐induced disturbances through integrated force–slip feedback. This work delivers the first miniaturized optical fingertip unifying underwater grasping and environmental perception, establishing a new paradigm for real‐time, robust underwater multimodal sensing, manipulation, and intelligent ocean‐interaction technologies.