應用於生物感測的表面電漿共振光纖探針之大量製作方法與其功效初步檢驗

Abstract

近來，在光纖端面製作次微米金屬結構並應用於表面電漿共振感測十分受到矚目，到目前為止已經發展了許多應用。因此，表面電漿共振光纖探針的需求與日俱增。其中表面電漿共振光纖探針的大量製作方法，是我們在本篇論文的主要焦點。 在此論文中，我們先介紹表面電漿共振光纖探針的製作過程。光纖探針的大量製作由光纖集束來實現，但由於此光纖集束即使在研磨後，仍然無法得到適合阻劑旋塗的平面，我們應用了奈米轉印技術來克服這項問題，此技術靠著材料之間表面能的差異來轉移金屬結構。我們選用聚二甲基矽氧烷做為轉印過程中印章的材料。在製作含有週期結構的印章的過程中，圖案的設計是藉由我們實驗室特有的雙光干涉曝光系統來完成。然而在將複製圖案至印章時，我們發現印章圖案在次微米的尺度下會有結構黏合的問題，此問題是因未固化的小分子而起並可由一些有機溶液或加長固化時間來減緩。將處理過後的印章鍍上金屬後，我們先於玻璃基板上進行奈米轉印並優化參數，而後才將優化的參數應用於光纖集束上。經由一系列量測結果顯示轉印結果良好，並且製作的結構為一三維結構。 為研究表面電漿共振光纖探針的光學特性，我們引用了FDTD Solutions與Comsol兩套商業軟體。模擬結果預測了反射與穿透頻譜的趨勢，同時表面電漿共振的位置與特性也被探討與證實。在外界環境的模擬當中發現到，穿透頻譜中的共振位置隨著環境改變而飄移，但另一方面，由於三維結構製作完整，反射頻譜並不隨環境而改變。在實驗量測的部分，頻譜量測結果與模擬結果有高度的相似性，證實了模擬模組的可靠性。藉由多重頻譜的重疊，暗示了利用奈米轉印技術達成表面電漿共振光纖探針大量製作的潛力。穿透頻譜在折射率感測方面亦有良好的表現，在共振位置之靈敏度為265.7 nm/RIU。本論文最後則示範以該光纖探針進行牛血清蛋白之生物感測。

To date, fabricating metallic submicron structures on an optical fiber facet and applying to the surface plasmon resonance (SPR) sensing have drawn a lot of attentions, and have led to many applications. Therefore, the need of SPR fiber probes increases steadily. The method for mass production of the SPR fiber probes is the main focus of this work. In this work, we first introduced the processes for the fabrication of the SPR fiber probes. The mass production of the probes was realized by fiber bundles. However, even if the bundle was polished, it could not generate a suitable plane for the spin-coating process of the resists. The nanotransfer printing (nTP) technique was adopted to overcome this problem. The technique relied on the different surface energies between the materials to transfer the metallic structures. PDMS was chosen as the material for the stamps used in nTP process. In the process of the fabrication of the stamps patterned with periodic structures, the patterns were designed by our unique two-beam interference lithography (IL) system. Nevertheless, it was found that the patterns on the stamps buckled up during the replication of the patterns to the stamps. The problem resulted from the uncured low molecular weight (LMW) chains, which could be removed by some organic solutions or a longer curing time. After a metallic layer was deposited on the treated stamps, we first applied the nTP process on the glass substrates and optimized the parameters. Then the optimized parameters were applied on the fiber bundles. To study the optical characteristics of the SPR fiber probes, two commercial software, FDTD Solutions and Comsol, were used in this study. The simulated results revealed the trends of the reflection and transmission spectra and the characteristics of SPR were also confirmed and discussed. In the simulation of different surroundings, the resonant position in the transmission spectrum shifted as the surroundings changed while the resonant position in the reflection spectrum remained still due to the structures’ insensitivity to the surroundings. In experiment, the measured results showed very good consistency with the simulated, which verified the reliability of the models used in the simulation. Based on the spectra obtained from different probes, the potential for mass production of the SPR fiber probes is found by utilizing fiber bundles and nTP technique. The transmission spectra showed good performance in refractive index sensing with a sensitivity of 265.7 nm/RIU for the resonant position. Finally, biosensing of bovine serum albumin (BSA) with the SPR fiber probes was demonstrated.