水氣的存在與介電層材料的親水性對有機薄膜電晶體感測氨氣的影響

Abstract

肝病為盛行於台灣的疾病，可堪稱為國民病。多數人罹患慢性肝炎後，約有5%的機會會轉變為肝硬化，為一種嚴重且不可逆的病變，目前沒有理想的治療藥物。一般透過侵入式方法監控肝病患者的血氨濃度，當超過血氨的正常值約每百毫升5~50毫克，患者依個人耐受性不同即會產生肝昏迷現象，故使氨氣成為肝病患者的監控指標之ㄧ。肝硬化患者多為居家照護，因此發展非侵入式的氨氣感測器監測患者的血氨濃度可幫助監控患者的病程，並提供肝昏迷一個預警機制。有研究報告指出肝硬化病者之呼氨濃度為0.745 ppm高於正常未患病者0.278 ppm。 有機薄膜電晶體 (OTFTs) 可被大面積製造、具低成本、可拋棄式的優點，適合用來開發非侵入式醫療診斷感測產品或環境監測上之應用。於前期實驗中，已開發出對氨氣具有高靈敏感測之元件 (可偵測最低氨氣濃度0.5ppm)。我們推測當水分子存在時，氨氣極易與之結合形成銨離子 (NH4+)。而銨離子為主要影響有機薄膜電晶體的感測能力。在本研究中旨在探討水分子濃度的提升影響銨離子的形成且增加元件電性的變化量。其次，我們改變元件介電層的材料：PMMA及PVP，利用材料的親水特性吸引水分子靠近，能形成更多銨離子，進而與元件作用，提升氨氣感測的靈敏度。

Liver disease is common in Taiwan. Most people infected with hepatitis B or C develop chronic liver disease; less cases of liver disease are caused by alcoholism and fatty liver diseases. Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrous scar tissue. Cirrhosis is generally irreversible and no has ideal medication for therapy. When the liver is dysfunctional, nitrogen compounds cannot be metabolized to ammonium (NH4+); however, ammonia (NH3) is an important indicator for chronic liver disease. Reports have shown that breath ammonia levels are significantly higher in cirrhotic patients (0.745 ppm) than in healthy subjects (0.278 ppm). Organic thin film transistor (OTFT) is a promising non-invasive, inexpensive, portable, and disposable diagnostic device because of its low-cost fabrication process and high-sensitivity to gas molecules. In our previous study, the OTFT sensor was sensitive to ammonia gas of 0.5 ppm (parts per million), and did not respond to carbon dioxide, ethanol, formaldehyde or methane. Ammonia is highly soluble in water and binds with water molecules to form ammonium (NH4+). We propose that ammonium is a major factor affecting the sensing ability of OTFT. In this study, we raised water vapor content to form more ammonium ions and enhance the change of electrical characteristics. Second, we chose two materials, PMMA and PVP as a dielectric layer of OTFT. Based on the fact that PVP is more hydrophilic, we discovered that raising water vapor content enhances the ammonia sensing ability of OTFT.