Janus Wettable Mask with Integrated Ratiometric Fluorescent Probe for Comfortable Exhaled H₂S Gas Sensing

The exhaled H₂S gas is considered a promising noninvasive, rapid biomarker for diagnosing oral health and respiratory diseases. However, there is an urgent need in the healthcare industry for a sensitive, accurate, low-cost, and comfortable wearable breath sensor for H₂S detection. Herein, a Janus wettable mask was developed by integrating the ratiometric fluorescent probes and asymmetric wettable fabric into the interior of the mask, for the comfortable and visual detection of H₂S. The Janus wettable mask with unidirectional biofluid transport capabilities can quickly transfer liquids from the hydrophobic side to the hydrophilic side, ensuring the dryness of the face during prolonged mask wear. The fluorescent color change from red to blue on the mask sensor can be observed by the naked eye under ultraviolet light, which enables evaluation of the H₂S gas concentration within a linear range of 1-100 ppb, and a low detection limit of 0.8 ppb. On-body experiments confirmed that the mask accurately detects exhaled H₂S gas and effectively captures the dynamic variations in H₂S gas levels at different times of the day. This study provides new insights into developing user-friendly wearable sensors and offers innovative solutions for reducing the burden on healthcare systems.