Smart Face Masks as Wearable Respiratory Sensors: A Review of Sensor Technologies, Materials, and Future Directions

Smart face masks are rapidly evolving into versatile wearable devices capable of simultaneously tracking a variety of physical and biochemical signals for both personal healthcare and environmental monitoring. This review focuses on respiration monitoring and highlights recent advances in materials, device architectures, and sensor design for mask-integrated platforms. We categorize current approaches into six sensor types, humidity, gas, temperature, pressure, strain, and triboelectric, and summarize their transduction principles, material/fabrication strategies, and representative demonstrations for quantifying respiratory metrics. Finally, we discuss key challenges for real-world use, including sensor cross-sensitivity, long-term stability, and user safety, noting that everyday activities like talking or head movement can affect measurements. We also highlight future opportunities in cost-effective manufacturing, modular designs, and AI-enabled data analysis to improve accuracy and reliability in respiratory monitoring.