微奈米結構設計於SPR生醫感測元件的應用

Abstract

表面電漿共振（Surface Plasmon Resonance）是一項新興的光學感測技術，它具有免螢光標定、高靈敏度、即時監控、多功檢測（生化反應、分子濃度）、可大量平行篩檢等優點。本研究著重於系統元件的改善，提出了一維的多層膜設計，和二維的光柵結構，以提高檢測能力。 以光學導納軌跡為理論基礎，我們設計一套非對稱式多層膜，來取代傳統SPR架構的單一金膜，利用兩種介電質材料（二氧化鈦、二氧化矽）高低折射率的週期性結構，結合雙金屬（金、銀）的設計，將共振角由原本的74°調變到61.52°，以及0.25°的信號半高寬，在量測系統的可觀察範圍內，不但擁有較大的動態量測角度，同時也具有較高的解析度及靈敏度。在實驗中，量測SPR信號的角度偏移、以及定角度下的反射強度變化，解析度可達8.13x10-6RIU。此外，利用不同之多層膜結構，進行不同波長穿透深度之解析能力，以模擬使用SPR技術來檢測奈米粒子在流體中位置高低變化的情況。 為了有助於將檢測系統微小化，我們使用以二維的結構陣列(Honeycomb)所組成週期約4μm的光柵，在833nm的入射波長以50°為入射角的選擇之下，同樣可以激發出表面電漿波，這種不需稜鏡耦合的結構，較易與其他元件整合，使系統在設計上更具彈性。

Surface Plasmon Resonance (SPR) is a novel optical sensing technique with advantages of label-free, high sensitivity, real-time monitoring, versatility (bio-chemistry reaction, concentration of molecule), and parallel detection. This research is focused on the improvement of system component , and we using the structure designs of 1D multilayer and 2D grating for enhanced performance. Based on the theory of optical admittance loci diagram, we designed a new asymmetric multilayer structure to replace traditional single gold layer. We applied the periodic refractive index change of two dielectric materials (TiO2/SiO2) combined with bimetallic design (gold/silver). SPR angle can be modulated to 61.52°, and reduced HMBW to 0.25°. The signal is located in the suitable range of measurement system, and our new device has not only a larger dynamic measurable range (1.33~1.48), but also higher resolution (8.13x10-6). In our experiment, we measured the angular shift of SPR and the reflective intensity change at a fixed angle. The resolution of the device is 8.13x10-6RIU. The multilayer structure was also used to simulate the position of nano-particle in micro-fluid channel. In order to minimize our detection system, we used the grating structure composed of 2D honeycomb array to couple surface plasmon wave and found at at proper incident wavelength of 833nm and angle of 50° has good SPR signal.