Air pollution becomes a global issue, while the air quality in Taiwan has rapidly deteriorated in recent years. As a result, an efficient and effective solution to monitor indoor and outdoor air quality has high business potential and industrial impact. Therefore, to establish a key technology chain in this rising field, the Taiwanese government endeavors to promote “Air Quality IoT” by leveraging the technology strength of sensors and the semiconductor industry in Taiwan. Among the key elements, PM2.5 sensors are of most importance for air quality monitoring where this sub-project aims to develop resonant type aerosol (PM2.5) sensing system through our mature MEMS technology. Thanks to low-loss micromechanical vibrating resonators, the proposed high-performance PM2.5 sensors feature high Q value, excellent mass resolution, fast response, and high sensitivity. The final goal of this sub-project is to form a reliable PM2.5 sensing module implemented and integrated into the overall “Environmental Hub” proposed by the main project. Currently, the precise air quality monitoring relies on bulky and expensive instruments, while the portable and affordable ones use optical detection method that suffers from low accuracy. PM2.5 sensor providing high accuracy with low cost is highly desirable, thus being the main target of this sub-project. This sub-project aims to deliver a miniaturized aerosol sensing unit in a four-year schedule with our industry collaborators’ help. It mainly focuses on the MEMS resonator, oscillator, and the related particulate matter sensing devices together with their sensing circuitry, calibration, and data analysis. The first year’s goal is to design, manufacture, and measure the thermally-actuated MEMS resonators and oscillators. To realize the MEMS oscillators, the sustaining circuit also needs to be used this year. Also, the measurement setup for both mass sensing and aerosol sensing will be built and evaluated. In the second year, we will complete designing and manufacturing a fully-differential MEMS resonator and oscillator to improve the device performance. The sustaining circuit (PCB electronics) will be designed and optimized to attain lower power consumption, enhance reliability, and reduce noise. The sensing range of the developed aerosol system is expected to reach 10~200μg/m3. In the third year, we will complete the aerosol sensor module based on the proposed oscillator frequency shift and set up an ambient particle measuring environment to prove the sensor’s specifications. In the final year, the proposed sensing module will be integrated with other modules from sub-projects 1, 3, and 4 on the same board with MCU and wireless module to realize sensor fusion, cloud computing, and data analysis for environment sensing hub applications.