Wearable, Breathable, and Wireless Gas Sensor Enables Highly Selective Exhaled Ammonia Detection and Real-Time Noninvasive Illness Diagnosis

Wearable gas sensors capable of real-time analysis of exhaled breath have been identified as ideal devices for noninvasive illness diagnosis. However, due to their inherent rigidity and brittleness, as well as high cross-sensitivity, conventional semiconductor gas sensors face significant challenges in achieving high flexibility, robustness, and selective exhaled breath analysis. Herein, we propose a wearable gas sensor by anchoring a SnS₂ nanosheets/polyaniline (PANI) sensing layer in situ onto a permeable and flexible yttria-stabilized zirconia (YSZ) nanofiber substrate for the analysis of exhaled NH₃. The cross-linked meshes of the YSZ network and the abundant voids between SnS₂ nanosheets effectively release the stress concentration in YSZ/SnS₂/PANI films, enabling the sensor to withstand severe folding/bending deformation. The organic PANI sheath endows the YSZ/SnS₂/PANI-based gas sensor with enhanced toughness (0.66 kJ·m^–3), stable electrical connection, and excellent robustness. The unique protonation/deprotonation sensing mechanism, coupled with the heterojunction effect of the sensing layer, ensures outstanding selectivity (sensor immunity coefficient ≈ 69%) and a high response to NH₃. To support wearable applications, the sensing signals from the wearable sensor are transmitted wirelessly via Bluetooth and displayed on a smartphone. This work greatly advances the application of a wearable semiconductor sensor in personal disease diagnosis.