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標題: | 錐形光纖探針檢測器於酒類與細菌檢測之發展與應用 The development and applications of tapered fiber tip for liquor quality and bacteria detections |
作者: | Yi-Hsin Tai 戴義欣 |
指導教授: | 黃定洧(Ding-Wei Huang) |
關鍵字: | 錐形光纖,近場光源,假酒,介電泳力,大腸桿菌,專一性檢測, Axicon fiber,near-filed light source,Fake wine,dielectrophoresis (DEP) force,Bacteria,specific detection, |
出版年 : | 2016 |
學位: | 博士 |
摘要: | 本論文利用蝕刻錐形光纖探針做為檢測的主軸,根據Snell折射定律,此錐形光纖在液體環境下,入射光於錐形光纖針尖內會形成全反射,形成相當程度的近場光源,在液體折射率由低變高時針尖的近場光會耦合至遠場,造成遠場繞射的光強度與光場分佈變化,此遠場訊號配合適當的收光面積,可以非常靈敏、即時的量測到微量液體的折射率變化,在論文中第一部份為利用此錐形光纖的近場光學特性,檢測假酒中的甲醇及水的含量。另外此針尖的近場光也會因微小透明顆粒的靠近,耦合至遠場,造成收光強度明顯的增強,在論文中第二與第三部份,由此技術結合介電泳力應用於偵測水中大腸桿菌含量,並利用離焦技術及特異性抗體修飾,提升大腸桿菌檢測靈敏度及專一性檢測能力。
論文的第一部份,是描述利用靈敏度高於5000 %/RIU並具有32°錐角的錐形光纖,來測量假酒的訊號變化,在量測不同濃度混合比例的乙醇與甲醇的液體時,從訊號變化可明顯看出,不同比例的混合酒其揮發速度與折射率變化的關係,利用預先量測出的標準折射率變化曲線,可做為鑑別假酒的參考值,同時也利用此光纖量測不同品牌的酒、檢測體積、溫度以及滲水的假酒各情況下的訊號變化,靠著量測初始的折射率值以及揮發速率曲線,可清楚辨別上述各個條件的差異情況。 在論文中第二部份裡引入介電泳力的應用,為了在針尖產生介電泳力以做為生物檢測的應用,於蝕刻光纖表面鍍上鈦及鋁金屬,並將交流電通入光纖針尖與相對應的透明導電玻璃上,藉此產生介電泳力,當外加電壓於鍍鈦及鋁光纖後,於量測1.36微米小球溶液以及大腸桿菌水溶液時,可利用介電泳力將小球及桿菌吸附於光纖尖端,達到聚集及快速檢測的效果,當小球及桿菌被吸附於針尖上時,針尖的近場光被散射,由遠場光強度可鑑別出各別的濃度差異,小球及大腸桿菌的檢測極限分別可達1 particle/mL及 20 CFU/mL。 在論文中第三部份介紹光學離焦技術及影像分析,藉此可進一步提升檢測靈敏度,靠著分析在不同蝕刻溫度下各光纖針尖的折射率靈敏度,找出最佳蝕刻的錐狀光纖角,利用離焦技術並配合最佳蝕刻溫度所製成的光纖,進一步提升光纖的折射率檢測靈敏度,在相同折射率區間下,離焦0.72 mm後的訊號強度變化比起焦平面提升約30倍以上。當在鍍鈦及鋁光纖上產生介電泳力檢測桿菌時,利用離焦技術及配合影像分析,與使用40x物鏡離焦0.1 mm的條件下,可獲得比起焦平面上訊號多2倍以上的變化量,此外於鍍鈦鋁光纖的針尖表面修飾專一性抗體,使光纖擁有專一性檢測菌種的能力,結合適當的介電泳力及配合流道內穩定的流速,可檢測出約低於103 CFU/mL的桿菌濃度。並用非專一性桿菌與專一性桿菌的測試比較,鑑定錐狀光纖檢測的專一性能力,而以此證明專一性桿菌比起非專一性桿菌有3倍以上的訊號變化。 This study explored some potential uses of a wet-etched axicon optical fiber. According to the Snell’s law, total internal reflection occurred at the interface between the axicon fiber tip and the surrounding medium while coupling light into the axicon optical fiber, a considerable amount of near-filed optical distribution were regenerated at the tip. When the refractive index of the surrounding medium was increased, the near-field light at the axicon fiber tip was coupled to the far field. And the light intensity and distribution for the far-field optical pattern were also changed. With the proper detection area, the variation of refractive index of small amount of liquid can be detected in real time owing to the high sensitivity of the sensing system. In the first part of the dissertation, the near-filed optical property of the axicon fiber tip was introduced for detecting the purity of wine mixed with methanol and water. Besides, the transparent particles close to the tip can also couple the near-field light to the far field. The collected optical intensity was significantly increased. In the second and third parts of the dissertation, the axicon fiber tip was introduced for detecting bacteria in water. Furthermore, the defocusing technique and specific modification were used to increase the sensitivity and the ability of the specific detection for the bacterial medium. In the first part of the dissertation, an axicon fiber tip at a 32° angle with a sensitivity greater than 5000% per RIU was introduced for measuring the signal change for mixtures of ethanol and methanol. At different volume ratios of these mixtures, the relationship between the change of the refractive index and the evaporation rate of the alcohol could be determined and the advance measure curve for the change of the refractive index could be used to identify impure wine. The axicon fiber tip was also used to detect different brands of wine, different volumes of wine, and wine mixed with water. Depending on the initial refractive index and evaporation rate, the signal can be clearly distinguished in the described conditions. In the second part of the dissertation, the application of a dielectrophoresis (DEP) force was described. For biological applications, the axicon fiber tip was coated with Ti and Al thin films, and an alternating current (AC) voltage was applied to the tip and an opposite indium tin oxide (ITO) substrate to generate a DEP force. For measuring mediums containing 1.36-μm polystyrene particles and Escherichia coli bacteria by using the coated axicon fiber tip, the DEP force was generated to attract the particles and the bacteria, allowing them to aggregate on the tip and reducing the detection time. The far-field light at the axicon fiber tip was scattered. The change of the refractive index in varying concentrations of the mediums could be distinguished by measuring the far-field intensity at the tip. The detection limits were 1 particle/mL and 20 CFU/mL for the particle and the bacterial mediums, respectively. In the third part of the dissertation, the defocusing technique and image analysis for increasing the detection sensitivity was described. The sensitivities of fiber tips at different etching temperatures were measured by image analysis, for determining the optimal etching angle. Etching the fiber at the optimal temperature with the defocusing technique considerably increased the sensitivity of the refractive index. When the fiber tip was used to measure the refractive index within the same range, the change of the signal at a 0.72-mm defocusing distance was 30 times higher than that at the focal plane. When the Ti/Al-coated fiber tip with the DEP force was used to measure the bacterial medium, the change of the signal at a 0.1-mm defocusing distance was twice as high as that at the focal plane determined using a 40× objective lens with the defocusing technique and image analysis. In addition, the surface of the fiber tip was immobilized with an antibody specifically for detecting K12 bacteria. Combined with the proper DEP force at a suitable flow rate in the channel, the measured detection limit for the K12 bacteria was 1.8 × 103 CFU/mL. For a specific competition experiment, the nonspecific BL21 and specific K12 bacteria were measured sequentially. The measured signal for K12 was 3 times than that for BL21. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/60131 |
DOI: | 10.6342/NTU201603803 |
全文授權: | 有償授權 |
顯示於系所單位: | 光電工程學研究所 |
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