水溶液環境原子力顯微鏡系統之設計與開發
Other Title
Design and Development of Atomic Force Microscope Systems for Liquid Environment
Date Issued
2013
Author(s)
Advisor
黃光裕
Abstract
在水溶液環境中之操作能力為原子力顯微鏡的重要優勢之ㄧ，此優點使原子力顯微鏡廣泛地被應用於生化研究的領域。然而，水溶液介質會嚴重影響微懸臂探針之動態特性，進而增加取得高解析與穩定影像的困難度。 在此篇論文中，分別探討微懸臂探針之幾何造型、激振機構、以及像散式偵測方法以改善在水溶液中之性能。考慮微懸臂尺寸，等比例減小微懸臂長度與厚度可提高Q值與共振頻率。此外，相較於微懸臂第一共振模態，高階共振模態可提供較高之質量靈敏度。在激振機構方面，開發之微懸臂夾持針座可有效減低水中之雜峰，並能提供彎曲式以及扭曲式兩種不同激振模式。藉由光路的修改，像散式偵測系統之靈敏度可被最佳化，並提高光學掃描模式對生物細胞成像之解析度。 最後，應用以上經驗開發一像散式偵測之水溶液原子力顯微鏡系統，水中雜峰可低於真實微懸臂共振峰值之26.0%。此外，藉由達到對石墨單原子層台階以及DNA樣品於水溶液中成像，驗證系統解析度以及量測軟性生物樣品之能力。
The ability to operate in liquid environment is a remarkable advantage of the atomic force microscope (AFM). This advantage enables the AFM to be applied to the bio-chemical field widely. However, the dynamic properties of the cantilever tip are influenced significantly in liquid, and cause the difficulty in getting high resolution and stable images. In this dissertation, the cantilever geometry, the excitation mechanism, and the astigmatic detection method are studied for improving the AFM’s performance in liquid. Considering the cantilever dimensions, the resonant frequency and the Q-factor can be raised through decreasing cantilever thickness and length proportionally. Besides, the high-order resonances can provide higher mass sensitivity than the fundamental one. In the excitation mechanism, a clamp-modification holder is developed for reducing spurious peaks and enhancing the real resonant peak, and provides a more apparent flexural or torsional excitation. Moreover, the sensitivity of the astigmatic detection system is optimized, and the resolution of the optical scanning method is also improved for imaging the bio-sample. Accumulating the experience above, a liquid-AFM system is developed based on the astigmatic detection method. The spurious peaks are suppressed down to 26.0 % of the resonant peaks in the liquid environment. Furthermore, it is verified that the liquid-AFM can realize high-resolution scanning images of the sub-nano scale graphite layer and the soft DNA sample in water.
Subjects
原子力顯微鏡
水溶液環境
像散效應
AFM
Liquid environment
Astigmatism
Type
thesis