Low-Power Wearable Breath Monitoring Device With Humidity- and Ammonia-Sensing Functions (May 2022)

Abstract

This article presents a wearable breath-monitoring device integrated with humidity- and ammonia-sensing functions. The breath-monitoring device was constructed using a piezoelectric cantilever array and hollow flexible polydimethylsiloxane (PDMS) membrane. Important parameters of breath, such as the respiratory rate and tidal volume, can be detected without actuated energy. The Nafion-based capacitive humidity sensor and ZnO nanoparticle-based resistance ammonia sensor were compactly integrated into the housing ring of a breath monitoring device. The fabricated humidity sensor demonstrated a faster response in the sensing range below 75% compared with a commercial product. The sensitivity of the fabricated ammonia sensor reached 0.16 ppm/mV and the sensor exhibited an approximately fourfold shorter response time compared with the commercial product. Two applications were tested for the developed device prototype. One was monitoring the humidity and ammonia of the environmental air along with breath parameters while breathing. The other was to examine the amount of breath air exhaled from the body of the subject. The total power consumed by the developed prototype device was approximately 46 mW, which is significantly lower than that of existing commercial products. This compact and lightweight prototype device demonstrates significant potential for wearable applications.