A recent study describes a new sensor developed by researchers from China and South Korea. The sensor uses ultrathin (~88 nm) amorphous indium gallium zinc oxide (IGZO) nanofibers for wireless and real-time monitoring of human breath.
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This advancement in room-temperature (RT) gas sensors is increasingly valuable in low-power Internet-of-Things (IoT) applications, such as smart sensors, wearables, and mobile robots. Metal oxide semiconductor-based sensors are particularly appealing due to their affordability, high sensitivity, and ease of use, making them ideal for detecting flammable, toxic, and exhaled gases. Yet, achieving further fiber diameter reduction and real-time monitoring integration remains a technical challenge.
IGZO nanofibers were created as the charge transport layer to enhance the surface area for gas diffusion using an electrospinning approach. The resulting field-effect properties demonstrated an average mobility of 2.2 cm²/V·s and an on/off ratio of 10⁵.
Qing Ma, Study Lead Author and Postdoctoral Fellow, School of Electronic Science and Engineering, Southeast University
The team effectively monitored different human breathing patterns—fast, normal, and deep—demonstrating the sensor's rapid responsiveness and reliable performance.
Ma added, “By integrating the sensor with a flexible circuit board and mounting them on a face mask, we achieved wireless and real-time monitoring of respiratory status, highlighting its potential for practical applications in health monitoring.”
Their research also uncovered that oxygen levels, water vapor, and temperature influence the sensor’s conductivity. When a voltage is applied, the sensor's current drops as someone exhales, then quickly recovers with each breath cycle, achieving a fast response time of about 0.7 seconds.
Senior and co-corresponding author Binghao Wang stated that this is a promising solution for pandemic prevention and personalized healthcare.
An IGZO NF-based sensor integrated into a flexible circuit achieved a compact size of 15 × 35 mm², marking significant progress in the miniaturization efforts for smart mask technology. The recorded electrical signals can be visualized via a smartphone equipped with a customized mobile app, underscoring the potential for the widespread adoption of IGZO TFT-based sensors in wearable technology.
Binghao Wang, Study Senior and Co-Corresponding Author, Southeast University
Journal Reference:
Ma, Q. et. al. (2024) Nanofibrous metal oxide semiconductor for sensory face masks. Wearable Electronics. doi.org/10.1016/j.wees.2024.09.001