Fast-response fully flexible Pd nanofilm-based hydrogen sensor for micro-leakage detection

To address the problems of insufficient conformal adaptability, difficulty in near-source detection, and response delay of conventional rigid hydrogen sensors in micro-leakage detection, this work proposes a flexible hydrogen sensor based on a Ti/W/Pd multilayer nanofilm structure, enabling rapid and in-situ hydrogen micro-leakage detection. Ti/W interdigital electrodes and a Pd hydrogen-sensitive film were constructed on a flexible PI substrate through photolithography, electron-beam evaporation, and lift-off processes, in which the Ti layer was used to enhance interfacial adhesion, the W layer served as the conductive electrode, and the Pd film acted as the core hydrogen-sensitive layer. SEM revealed wrinkles and gully-like features in the Pd film after hydrogen exposure, indicating hydrogen-induced structural reconstruction associated with PdH x -related lattice expansion, stress redistribution, and conductive-pathway modulation. XPS and XRD results further confirmed the metallic state characteristics and stable crystalline structure of the Pd film. Benefiting from the flexible Ti/W/Pd multilayer film structure and the efficient catalytic dissociation of hydrogen by Pd, the sensor achieved a response of 37.1% and a response time of 4.6 s toward 1% H 2 at room temperature, and the response time was further shortened to 0.5 s at 105 °C. The sensor exhibited distinguishable responses over the range of 4–40,000 ppm, as well as good repeatability, humidity adaptability, gas selectivity, and curved-surface attachment stability. A wireless hydrogen micro-leakage detection system constructed based on this sensor enabled real-time acquisition, transmission, and display of leakage signals, and showed superior near-source detection capability compared with a commercial MQ-8 hydrogen sensor in simulated micro-leakage tests at clamp connections, verifying its feasibility for application in complex connection and sealing structures.