Janus Wettable\nMask with Integrated Ratiometric Fluorescent\nProbe for Comfortable Exhaled H<sub>2</sub>S Gas Sensing

The exhaled H<sub>2</sub>S gas is considered a promising\nnoninvasive,\nrapid biomarker for diagnosing oral health and respiratory diseases.\nHowever, there is an urgent need in the healthcare industry for a\nsensitive, accurate, low-cost, and comfortable wearable breath sensor\nfor H<sub>2</sub>S detection. Herein, a Janus wettable mask was developed\nby integrating the ratiometric fluorescent probes and asymmetric wettable\nfabric into the interior of the mask, for the comfortable and visual\ndetection of H<sub>2</sub>S. The Janus wettable mask with unidirectional\nbiofluid transport capabilities can quickly transfer liquids from\nthe hydrophobic side to the hydrophilic side, ensuring the dryness\nof the face during prolonged mask wear. The fluorescent color change\nfrom red to blue on the mask sensor can be observed by the naked eye\nunder ultraviolet light, which enables evaluation of the H<sub>2</sub>S gas concentration within a linear range of 1–100 ppb, and\na low detection limit of 0.8 ppb. On-body experiments confirmed that\nthe mask accurately detects exhaled H<sub>2</sub>S gas and effectively\ncaptures the dynamic variations in H<sub>2</sub>S gas levels at different\ntimes of the day. This study provides new insights into developing\nuser-friendly wearable sensors and offers innovative solutions for\nreducing the burden on healthcare systems.