Development of a MEMS-Based Resonant Airflow Sensor for Apnea Detection Using Time-of-Flight Technique

This article introduces a novel micro electromechanical system (MEMS)-based resonant airflow sensor designed specifically for respiration monitoring in application such as obstructive sleep apnea (OSA). The sensor operates based on the time-of-flight (ToF) technique and employs thin-film piezoelectric-on-substrate (TPoS) resonators. The resonators operate at ~25 MHz and are integrated into two oscillator circuits the frequency of which varies with temperature and humidity. By measuring the flight time of the airflow between sensing elements, the sensor can precisely calculate flow rates and velocities. A carefully designed laminar airflow channel is incorporated to maintain nonturbulent flow, which is essential for the accuracy of ToF measurements. Experimental validation demonstrates the sensor’s ability to measure flow rates from 0 to 10 L/min and velocities from 0 to 2 m/s with high precision and linearity with an accuracy as high as 97.85%. These results represent a significant advancement in respiratory monitoring technology, offering a noninvasive and cost-effective solution for home-based detection and management of OSA.