부산대학교 도서관

In this article, we present a monolithically integrated multifunctional sensor for respiratory applications, which consists of a bidirectional micro flow sensor with dual microheaters and a stacked microelectromechanical systems (MEMS) temperature/humidity sensor. Importantly, the integrated multifunctional sensor is fabricated using a low-cost CMOS-compatible MEMS process. In addition, the MEMS humidity sensor is further coated with a polyimide (PI) layer to enhance its water absorption and sensitivity. The performance of each sensor is evaluated in conjunction with its interface circuit. The results show that the flow sensor has a high sensitivity of 0.62 mW/(m/s) $^{\mathrm {1/2}}$ within a detectable flow range of −12–12 m/s. The temperature sensor shows a sensitivity of −57.1 mV/°C over a linear range of 0 °C–50 °C, while the humidity sensor exhibits an average sensitivity of 15.8 fF/%RH. Moreover, the preliminary results from this monolithically integrated sensor in human breath monitoring, confirm its potential as a promising low-cost Internet of Things (IoT) node for respiratory applications.