Coaxial Hydrogel Optical Fibre Skin for Interference‐Free Multimodal Tactile Perception

ABSTRACT Flexible photonic fibers enable precise, interference‐free multimodal tactile sensing in wearable interfaces, owing to their intrinsic immunity to electromagnetic interference and cross‐modal coupling, together with rapid response. Until now, optical fibers that simultaneously exhibit mechanical robustness, signal decoupling, and environmental stability remain scarce, and system‐level integration is even rarer. Inspired by the distributed sensory arrangement of jellyfish tentacles, we propose a photonic skin composed of coaxially structured hydrogel optical fibers, in which pressure and temperature signals are routed through independent photonic and ionic channels for interference‐free multimodal sensing. The stretchable, highly reproducible, refractive‐index‐matched core‐cladding photonic fiber was constructed by continuous coaxial spinning with in situ photopolymerization. It resolves the long‐standing trade‐off between mechanical stretchability, low‐loss optical guiding, and temperature/humidity robustness in hydrogel fibers. The assembled sensing skin achieves high pressure and temperature sensitivity with a sub‐10‐ms response, surpassing existing benchmarks. It integrates with a lightweight, flexible printed circuit and multimodal tactile fusion machine‐learning architecture to form a wearable system, enabling wireless control, adaptive gesture recognition (99.21% accuracy), and multimodal object classification (99.22% accuracy). This work presents a fully integrated photonic skin platform bridging material‐level signal decoupling and system‐level multimodal perception for intelligent tactile interfaces in complex environments.