- 學位論文
烷基硫醇分子於空氣中自組裝於微懸臂梁金表面 之吸附行為探討
Adsorption Behavior of Self-Assembled Alkanethiols on Gold-coated Microcantilever in Air
摘要
近幾年來，因微機電產業的蓬勃發展，讓我們有機會利用微小尺寸的機械裝置作為感測器，開始從巨觀世界轉向觀察微米、奈米等尺度的世界。其中微懸臂梁式生物感測器可以將各式物理、化學反應轉換為力學能的形式，使人們得以進行量測，並因其高靈敏度以及容易偵測等優點，而成為生化領域上一種很重要的感測器。然而在有關於溫度變化對感測器的影響卻鮮少有機會探討，本研究的目的就是以這個面向為出發點，想知道感測器與待測物結合後，表面性質是否會有改變。 本研究以採用微懸臂梁以及光學量測平台，分別量測不同碳鏈長度的自組裝分子(self-assembled monolayers, SAMs)吸附於金表面所造成的表面應力，以及吸附過後金表面熱膨脹係數的改變。我們發現，短碳鏈以及長碳鏈對於表面應力以及熱膨脹係數的改變有不同的趨勢，而造成這個趨勢的原因，一是因為碳鏈之間的凡德瓦力作用，另一原因則是長碳鏈時整個系統的熵值較高。並且我們也經由長時間的實驗，得知長碳鏈的自組裝分子的表面應力會有震盪的趨勢，引發的原因應是自組裝分子在表面吸附的狀態從倒下轉為站立狀態。 完成實驗後，我們利用分子動力模擬進行不同碳鏈下熱膨脹係數的變化，以驗證實驗的正確性。最後提出與本研究相關實驗儀器上的改進，以及未來模擬所需要完成的方向。
並列摘要
With the advance of micro- and nano-fabrication technologies, the microcantilever sensor has now become an important nanomechanics-enabling device for biosensing. The microcantilever can transfer the physical and chemical interactions into mechanical responses that can be measured. The high sensitivity and low cost features of the microcantilever sensor have made it one of the promising candidates for future portable biosensing devices. The object of this thesis is to investigate the surface stress and thermal expansion coefficient of self-assembled monolayers (SAMs) adsorbed on gold-coated microcantilever beam. From the experimental result, we found that the anomaly between chain length and surface stress and thermal expansion coefficient. Van der Waals' force and entropy are responsible for the anomaly when chain length is long. In addition, measurement fluctuation of the long chain length SAMs’ surface stress is contributed to those molecules changing their configuration from lying-down to standing up. In the simulation part, we use molecular dynamics to prove the correctness of the experiment which is related to the thermal expansion coefficient. And we found the simulation’s result and the experimental result show the same anomaly between chain length and thermal expansion coefficients.