Breath-to-exercise monitoring via ultrafast SnO2-LSMO humidity sensors

Non-contact humidity sensing shows great promise for respiratory monitoring, offering a non-invasive pathway to assess physiological health. However, the translation of existing humidity sensors into practical applications is limited by slow response, poor selectivity, and susceptibility to environmental interference. Here, we report a co-doping strategy in which La, Sr, and Mn were incorporated into SnO 2 using La 0.7 Sr 0.3 MnO 3 (LSMO) precursors using a hydrothermal route. The SnO 2 -10LSMO based sensor exhibited superior performance, including an ultrahigh response (∼80,000), fast and repeatable dynamics, and excellent resistance to interference. Compared with nitrate-doped counterparts, the performance enhancement is attributed to the uniform distribution of dopant ions and optimized electronic structure. Importantly, real-time breath analysis demonstrated the ability to distinguish different breathing frequencies, enabling a portable platform for exercise intensity monitoring.