射出成型波導模態共振生物感測器 之表面孔洞效應分析

Analysis of Sub-surface Cavities on The Performance of Injection-Molded Guided-Mode-Resonance Biosensors

古逸凡(Yi-Fan Ku)

指導教授 ： 張國恩

國立中正大學/工學院/機械工程學系/碩士(2015年)

摘要

本文之研究方向主要分成兩個大項，第一為探討表面孔洞效應對於雙面光柵波導式生物感測器靈敏度提升與其光學性質之影響，第二為發展以光強度做為偵測機制之低成本，高靈敏度生物晶片感測平台。
在雙面光柵波導式生物感測器靈敏度提升中，我們可藉由調整濺鍍之工作氣體氧氣與氬氣比例的不同，其能使波導光柵與基板之間產生表面孔洞，而實驗證實這些表面孔洞能夠有效的增加生物感測器性能，而引入孔洞後之感測器靈敏度可大幅增加至184.06 nm/RIU，與沒有孔洞之生物晶片相比足足提升了211%。接著我們用有限元素模擬將孔洞群定義為多孔性結構層，而我們在結果發現，這些表面孔洞會使基板之等效折射率降低，如此電場能量分佈將會往待測物方向飄移，這不僅能夠使漸逝波面積增加，還能夠使穿透深度變長，因此生物感測器所能偵測到待測物的範圍就會變大，感測器靈敏度就會因此提升；此外我們還發現多孔性結構層之折射率變化與感測器靈敏度關係並非線性，當多孔性結構層折射率接近待測物折射率時，感測器靈敏度將有顯著的提升。
在低成本之生物晶片感測平台系統上，我們使用低成本綠光發光二極體做為入射光源，以及利用光偵測器作為光偵測單元，並利用偵測光強度的大小做為檢測機制，這不僅僅能夠使生物感測器之性能提升，更能夠大幅降低檢測平台之成本。由實驗結果發現，在實驗架構中加入雷射光濾波片或短波長濾波片能夠增加正規化靈敏度55%，折射率解析度最佳為7.58×〖10〗^(-5)RIU，已可與其他光學式生物感測系統比擬，且具有低成本的優勢。
本文所發展的雙面光柵波導生物晶片感測系統具有低晶片製作成本、低感測平台成本與高靈敏度，在未來可在生醫檢測、食品摻偽檢測等方面有所應用。

關鍵字

模態共振 ； 生物感測器 ； 波導 ； 雙面光柵

並列摘要

This study focuses on improving the performance of injction-molded guided-mode resonance biosensors. Two main topics are included: (a) enhancement of sensitivity via-subsurface cavities, and (b) development of low-cose, high-sensitivity low-cost, label-free intensity-resolved optical signal acquisition platform.
On the topic of sensitivity enhancement, sub-surface cavities are created at the interface between the waveguide and cyclic olefin copolymer (COC) substrate by adjusting the sputtering parameters. As the oxygen content increases in the sputtering process, the mean cavity size is increased, and the sensitivity is enhanced by 221%, in comparison to a reference GMR sensor without a cavities. Finite-element-method simulations are performed to analyze the effect of cavities. The results show that the cavities decrease the effective refractive index of the medium beneath the waveguide and significantly redistribute the resonance mode profile. As a result, the evanescent wave is extended toward the sensing area and the penetration depth is increased. In addition, we find the relationship between the refractive index of cavity layer and the sensitivity is nonlinear. As the refractive index of cavity layer approaches that of analyte, the sensitivity is significantly enhanced.
For the development of label-free intensity-detection signal acquisition platform, the detection is built based on transmission experiments using a low-cost green light-emitting diode as the light source, and a photodetector as the detecting unit. With the spectrum-limited light source, the intensity of transmission light becomes convolution of LED and GMR transmission spectra, successfully converting the GMR shifts to intensity changes. Our experiments show that a refractive index resolution of 7.58×〖10〗^(-5) RIU is achieved. This present investigation demonstrates a low-cost, label-free, high sensitivity bio-sensing platform for practical applications in food adulteration, bio-medical and chemical detection.

並列關鍵字

biosensors ； waveguide ； double-side grating ； guide-mode resonances

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