量測微粒重量濃度與粒徑分佈之微型感測器之開發

Development for Measuring Mass Concentration and Size Distribution in Micro Particle Sensor

梁道(Dao Liang)

指導教授 ： 陳俊杉

共同指導教授 ： 施文彬(Wen-Pin Shin)

國立臺灣大學/工學院/土木工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01023

摘要

室內空氣品質IAQ（indoor air quality）是判斷室內環境的舒適度或工作場所的安全性之重要指標。空氣品質的好壞，取決於其中污染物的多寡，而空氣污染物則泛指懸浮在空中微小物質。量測微粒濃度的方法，目前以光學的方式為主流，不過因為光路設計複雜，儀器的體積始終無法小型化，且對於微粒重量濃度的測定，必須要已知顆粒本身的材料密度，經由量得特定粒徑大小之數量，推算出重量濃度，故無法量測當有不同種類微粒混和時的重量。
本研究的目的旨在於發展一微型微粒感測器，能夠在不同環境中，量測出空氣中粒徑的分佈及分類後各微粒尺寸之重量濃度，並在研究初期嘗試以不同原理開發感測器元件，包括壓阻式懸臂梁感測器、光阻式感測器及電容值感測器。在研究後期利用虛擬衝擊器的概念製作粒徑分類之元件，及使用石英振盪器其負載質量改變時會造成共振頻率偏移的特性，來測量當微粒吸附於其上時的微粒重量。將這兩種元件整合其架構，透過實驗的方式找出其特性，進而實作出具有粒徑分類及微粒重量量測之微型微粒感測器。
本研究所製作之各式微粒感測器功能雖不完整，但各有已完成之部份成果。壓阻式懸臂梁感測器的實驗中，發現到製作出來的懸臂梁勁度過強，導致置於其上的微粒無法使其產生變形，而若能使懸臂梁勁度降低，配合CMOS電路及統計學的概念，將可實作出可量測微粒大小及數量的微粒感測器。在光阻式感測器的實驗中，雖無法經由輸出電壓值大小，推算出微粒數，但仍可藉由觀察輸出電壓曲線的peak數，計算出通過流道的物體數量。電容值感測器的想法，經過計算後，發現電容值變化太小，無法利用於粒徑小的微粒，但若是偵測大粒徑或是介電係數大的顆粒，應有較大電容值變化，同樣利用CMOS電路及統計學的概念，可實作出量測微粒大小及數量的微粒感測器。
虛擬衝擊器的實驗結果雖不如預期，但仍可將顆粒分為2.282μm以下、3.15~2.282μm之間及3.15μm三種尺寸。在QCM的實驗中已將其特徵曲線找出，可利用來推估QCM所吸附到的微粒重量。

關鍵字

室內空氣品質 ； 微粒 ； 感測器 ； 虛擬衝擊器 ； 石英震盪器 ； 氣膠 ； 共振頻率

並列摘要

IAQ (indoor air quality) is an important indicator for determining indoor microclimate and comfort. The indicator depends on the amount of pollutants in the air. The air pollutants refer to suspension with very small particles in the air. The optical instrument is the de-facto way to measure the concentration of particles in the air. Nevertheless, the design of such instrument is often too complicated to decrease its volume. In addition, the density of the particles must be known a priori in order to calculate weight concentration. It thus limits its capability to examine the weight of particles with mixing materials.
The objective of this work is to develop a miniature particle sensor to detect the distribution of particles and concentration of weight of each particle size in the air, and try to develop the element of sensors by different principles at the first stage of this work. These include Piezoresistive Cantilever particle sensor, Light Blockage particle sensor, and Capacitance particle sensor. At the second stage of this work, we made the element of particle size distribution by the conception of Virtual Impactor, and QCM (Quartz-crystal microbalance) is used to measure the mass of particle loading by utilizing its characteristic of resonance frequency shift. We integrate the frame of those two devices and find the property of them by experiment. Finally, we have designed and fabricated the particle sensor which can sort out the particle size and measure the mass of particle.
Several insights were gained in this work. In Piezoresistive Cantilever particle sensor, we found that the stiffness of cantilever is too high to be deformed. If we can decrease its stiffness and use the CMOS circuit and conception of statistics, we can produce the particle sensor which can measure the size and number of particle. In Light Blockage particle sensor, although we could not calculate the number of particles by the voltage difference, we were able to count the number of particles by observing the peak number of the curve of the output voltage. The variation of capacitance in Capacitance particle sensor was too small to detect the small size particles. Nevertheless, it might be useful to detect particles with larger size or larger dielectric constant.
Virtual Impactor developed in this work could be used to classify particle diameter in three different ranges, <2.282μm, 3.15~2.282μm, and >3.15μm. We have also identified the characteristic curve of QCM for mass detection. Using QCM with virtual impactor, we have demonstrated a sensing prototype to calculate the mass of particles adhering to QCM.

並列關鍵字

IAQ ； Particle ； Sensor ； Virtual Impactor ； QCM ； Aerosol ； Resonance Frequency

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