Smart Supramolecular Humidity Sensors Based on Crystalline Organic Cages for Noninvasive Freshness and Respiratory Monitoring

Noninvasive monitoring is most powerful when physiologic and environmental signals can be captured without contact or sample destruction, using materials that respond rapidly, remain stable, and integrate easily into wearables. Despite its growing impact across health, safety, and quality assessment, there is still a clear gap in materials that simultaneously deliver high sensitivity, long-term stability, and device-level compatibility. Smart supramolecular sensing (SSS) platforms-built on dynamic, reversible intermolecular interactions-offer a compelling strategy for next-generation noninvasive monitoring technologies. Here, a crystalline N3O3 organic cage-based humidity-sensing SSS system is reported that exhibits ultrafast response, exceptional reversibility, and long-term operational stability. Comprehensive theoretical and experimental analyses reveal that the compact cage architecture fosters a robust supramolecular network, which facilitates Grotthuss-type proton hopping and enables high-performance sensing. Practical utility in two representative is demonstrated, noninvasive scenarios: i) contactless evaluation of fruit surface moisture for freshness assessment, and ii) wireless respiratory monitoring using a smart facemask that continuously tracks exhaled humidity patterns and can flag abnormal breathing behavior. These findings position SSS platforms as robust and versatile building blocks for the development of the next-generation wearable and noninvasive monitoring technologies.