Breath monitoring based on the optical electronic nose system

The identification of volatile organic compounds (VOCs) presented in exhaled human breath can provide direct evidence of the health status of patients. Electronic nose (e-nose) has been known as an efficient technique for odor classification of numerous products, living and non-living objects and environment. In this work, an optical e-nose system that consists of organic thin film gas sensor and optical detection system was investigated on its potential for biomedical applications. The gas sensor was prepared based on metal-porphyrin compounds that are the optically active to various basic VOC. In addition, low-cost light emitting diodes (LEDs) array and a CMOS photo-detector were integrated to analyze the color change in the sensing material. The sensing materials were tested with various common VOCs, for examples, alcohols, acetone, ammonia and water. Pattern recognition, namely principal component analysis (PCA), clearly distinguished the different concentration of ammonia vapor, and discriminated ammonia from acetone vapor. Moreover, optical e-nose successfully detected the change of exhaled breath such as before and after eating. Consequently, this system is expected to be further developed as a breath monitoring system.