A Room-Temperature Dual-Gas Humidity/Ammonia Sensor Based on Gallium Oxide for Breath Analysis

Abstract

The analysis of human breath to detect both respiration state and breath biomarkers is of great importance in the fields of exhaled noninvasive breath monitoring and diagnosis. Thus, we have elaborately synthesized gallium oxide (Ga2O3) with different oxygen species as humidity and gas sensitive materials to monitor respiratory function and ammonia (NH3). In this work, the sensing characteristics and breath monitoring applications of the humidity/ammonia sensor based on the Ga2O3 are systematically investigated. The humidity sensor demonstrated high responsivity (over three orders of magnitude), low humidity hysteresis (1.83%), and good long-term stability. The ammonia sensor has a response of 1.2% to 2-ppm ammonia at 70% relative humidity. To investigate the potential application of the sensor in detecting ammonia in exhaled gas, a simulated breath test was conducted.