可攜式PM2.5感測系統之開發

Development of a Portable PM2.5 Sensing System

蔡博存(Po-Tsun Tsai)

指導教授 ： 田維誠

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.01201

摘要

氣喘病人容易對於環境之許多物質感受到刺激而引發氣喘，而在空氣汙染此因素中，多環芳香烴化合物(PAHs)為其中一項危害氣喘病人且引發氣喘之有毒物質，而此類物質多附著於PM10及PM2.5之表面，又因為PM2.5之影響範圍相當廣，故對於PM2.5之偵測及提供警訊對於氣喘病人是相當的重要，而現今準確之偵測設備多為固定式量測，對於氣喘病人之監控其實相當有限。此外，其分析機器也是相當之昂貴。
本研究嘗試設計一即時分析且可攜性之氣體微粒感測器，期許能使氣喘病人隨身攜帶且即時監控其身處環境之有害物質濃度，使得醫生能對其病人之病症有更完善的參考資料，使得能更精準的判斷且給予病人建議，給予病人更完善的醫療診斷。其中感測器有石英晶體微天平(QCM)及CMOS MEMS電容感測器兩類，但在本研究中，QCM僅能量測PM10之粒子；CMOS MEMS感測器則是以商用製程TSMC CMOS MEMS 0.35μm 2P4M平台下線，再由本團隊進行後製程及封裝處理，此CMOS MEMS感測器以梳狀電容做為微粒感測器之結構，當微粒進入到感測器時，改變梳狀電容的介電常數，使得電容值因此增大，以此來測量空氣中微粒之多寡及濃度，其感測器在不同的條件下所得之敏感度為1.00*10^-2~1.20*10^-2pF/μg，並且可量測濃度最低可至20μg/m^3；而在三種間隙對於PM2.5粒子之落入程度的比較，4μm間隙之落入程度遠大於8μm、12μm之落入程度。系統則結合可攜式抽氣幫浦、感測器、動態量測電路、後端電腦數據處理以及溫濕度計，故可利用此系統快速的計算粒子濃度，使得實現可攜且即時分析的微粒感測器；此外，利用溫濕度計及實驗前校正，可大量去除溫濕度對感測器所造成之誤差，使得感測器較為忠實的呈現粒子落入間隙之反應。

關鍵字

微機電系統 ； PM2.5 ； 石英晶體微天平 ； 電容感測器 ； 梳狀電極電容 ； 可攜式系統 ； 微粒感測器 ； 氣喘

並列摘要

Asthma attacks of the patients can be triggered by several environmental pollutants. One of the most significant pollutants in our environmental is PM2.5 particles (diameter of the particulate matters smaller than 2.5um). Some of poisonous materials such as polycyclic aromatic hydrocarbon (PAHs) are easily attached to the surface of PM2.5 particles and can be absorbed by the asthma patients through breathing or food chain. Traditional measurements of PM2.5 are typically performed in a fixed station. However, this measurement by a station is not suitable for the real time monitoring to track the asthma patients activities. In addition, the analysis system of the PM2.5 is also very expensive.
In this research, we aimed to develop a real time and portable particle sensor which asthma patients can use to monitor their exposure during daily activities. The system consisting of a portable air pump, a sensor, an interface circuit and a laptop can monitor the particle concentration and calculate the real time data simultaneously. Two sensors were characterized in this study. The first one is a commercially available QCM and the other one is a CMOS MEMS capacitance sensor with the comb structures fabricated through a commercial 0.35μm 2 polysilicon and 4 metal CMOS MEMS process followed by the self-developed post processes. The comb structure design has 104 gaps between electrodes. When PM2.5 particles fall in between the gap, the dielectric constant in between two electrodes is increased, and then the overall capacitance value of the sensor is increased as well. The sensitivity of the sensor is approximately 1.00*10^-2~1.20*10^-2pF/μg under different environmental conditions. Finally, the influences of humidity and temperature were removed from our study with a model and a portable and real time air quality monitoring for asthma patients can be realized.

並列關鍵字

MEMS ； CMOS MEMS ； PM2.5 ； Portable system ； QCM ； Comb structure capacitance ； Particle sensor ； Asthma

參考文獻

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