▎ 摘　　要

Due to the strong liquid intermolecular force, feasible sensing-detection methods in liquid environments are absent. Inspired by fish swim bladder, herein, a hollow-structured microfiber is designed to realize high-performance sensing in liquid environments. It composes of 2D polypyrrole (2DPPy) and reduced graphene oxide (rGO), and its wall has a porous skeleton of 2DPPy/rGO/2DPPy (2DPrG2DP). The internal cavities of porous skeleton will be filled by the liquid, while leaving a bubble inside the hollow micropipe due to the liquid surface tension, thus forming a solid/liquid/gas triple-phase interface. This hollow microfiber transforms the unmanageable liquid-phase sensing into gas-phase sensing. During this process, the good mechanical strength of 2DPPy enables the high sensing operability, and the reversible gas extrusion-withdraw process enables the high sensitivity. The hollow 2DPrG2DP microfiber-based sensor can be potentially used to machine trouble shooting, water level monitoring, ocean current monitoring, tsunami warning, body fluid and blood monitoring, and oil transportation monitoring.