具銀膜加熱器之微型前濃縮晶片應用於微型氣相層析系統

Abstract

本研究為開發一種微型前濃縮晶片(Micro Preconcentrator, μPCT)，其為微型氣相層析系統 (Micro Gas Chromatography, μGC)之關鍵元件，氣相層析系統可針對人體所呼出之氣體混合物進行詳細分析，並以非侵入的方式監控人體健康狀況及提前預防肺部相關等疾病，亦可應用於環境監測及空氣汙染檢測等方面。 本研究所提出之微型前濃縮晶片，相較於其他研究團隊之設計，於微流道內製作有高加熱效能之微銀膜加熱器，其透過簡易的微機電製程(MEMS)技術，僅須一道光罩，並結合微流體技術及化學還原反應(多倫反應，Tollens’reaction)即可達到，大幅降低製程所需之時間和成本。並且針對先前研究之前濃縮晶片於量測上所碰到的缺點，進一步加以改善與改良，且可就其填入之吸附劑不同，能吸附不同物性之氣體化合物。並利用微加熱元件，能有效地將吸附之氣體進行分離與濃縮,達到高度的氣體選擇性及氣體濃縮效果。 本研究之μPCT將整合於氣相層析系統，以纖維素燒結碳化之碳膜作為吸附劑，進行揮發性有機氣體(Volatile organic compounds, VOCs)之量測與分析。當輸入功率為5 W時，具有50℃/s 之加熱速度，到達熱脫附之溫度僅需6秒，實驗中以濃度為10 ppm、1ppm、100ppb之Acetone、Benzene及Toluene作為待測氣體，脫附之氣體樣品將經過長度為17公尺之石英分離管柱進行分離，最後再經由火焰離子感測器偵測分離後氣體之訊號並加以分析。新設計前濃縮晶片採樣流速為過去設計的十倍，解決過去研究流阻過高、採樣流速過低的情況，濃縮容量亦較過去設計大，並可針對濃度較低(100ppb)之樣品氣體進行濃縮，濃縮效能表現更好。

We developed a micro preconcentrator (μPCT) for the micro gas chromatography (μGC), which can be employed to analyze the human exhaled breath for the non-invasive monitoring of the health condition of human body. It is believed that one can detect some lung related diseases and apply this device to the environmental and air-pollution monitoring. A simple micromachined process s based on one photomask combined with microfluidic technique and the Tollens’ reaction is developed for a novel μPCT. The new design of the μPCT solved some problems and shortcomings that previous design encountered during the experiments and the measurements. With high efficient thermal capability and sufficient adsorption capacity, we could coat different kinds of adsorbents to adsorb several targeted gases in μPCT, concentrate the trace analytes, and separate them successfully by its heating element, thus improving the selectivity and the concentration effect of gases. With the micro silver heater, the μPCT can be heated to 300℃ rapidly by applying a constant electrical power of ~5 W with a heating rate of 60℃/s. Three volatile organic compounds (VOCs), acetone, benzene, and toluene, are collected through the proposed novel μPCTs and separated successfully using a 17-m-long gas chromatography (GC) column. The sampling flow rate of the novel μPCT is ten-fold faster than previous design, and the novel μPCT is able to concentrate sampling gases with lower concentration (100ppb). The novel μPCT has better and more efficient performance in concentrating.