Humidity-Independent, Breathable and Wearable Chemiresistive Sensor Enables Exclusive Exhaled Ammonia Detection.

Breath analysis offers a promising noninvasive diagnostic strategy by capturing volatile biomarkers associated with systemic metabolism. However, existing wearable sensors are hampered by limited sensitivity, insufficient selectivity, and pronounced susceptibility to humidity under practical exhaled breath conditions. Herein, we present a wearable exhaled ammonia (NH3) sensor based on a self-supporting composite nanofiber film composed of yttria-stabilized zirconia (YSZ), titanium dioxide (TiO2), polyaniline (PANI), and sodium dodecylbenzenesulfonate (SDBS). The YSZ nanofiber network ensures mechanical flexibility and structural integrity, while the PANI/TiO2 heterojunction enhances NH3 adsorption and signal transduction, achieving a low limit of detection (300 ppb NH3) in the presence of interfering gases and high humidity (≥80 RH%). The hydrophobic SDBS modification effectively mitigates water co-adsorption, enabling stable sensor performance under high-humidity conditions. Integrated with a wireless sensing platform, the wearable sensor successfully monitors simulated exhaled NH3 in real time through mobile terminal. This work represents a significant advancement toward the development of robust, humidity-resistant wearable gas sensors, paving the way for non-invasive health monitoring and early disease screening.