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  • 學位論文

整合微球面反射鏡於懸臂樑自由端之設計與應用

The Design and Applications of the Cantilever with an On-Tip Micro Spherical Reflecting Mirror

指導教授 : 蔡睿哲
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摘要


藉由整合微球面反射鏡(Micro spherical reflecting mirror)於懸臂樑感測器的自由端(Free end),反射光束的光偏折角(Optical deflection angle) 將可以被有效地放大,也就是能夠增加投射在位置感測器(Position-sensing detector, PSD)偵測面上的光偏折位移(Optical bema displacement),進而提升懸臂樑感測器所搭配之光學偵測系統的靈敏度(Sensitivity/responsivity)。而微球面反射鏡之曲率半徑的設計,將決定光學系統靈敏度所能提升的程度。如果給定一個懸臂樑自由端偏折量(Tip displacement)以及一段固定的距離(懸臂樑自由端到PSD偵測面的垂直距離),整合曲率半徑較小的微球面反射鏡之懸臂樑感測器能夠產生較大的光偏折角,也就是增加光束在PSD偵測面上的光偏折位移。因此,整合微球面反射鏡之懸臂樑感測器(Micro spherical reflecting mirror integrated cantilever, MSRM-integrated cantilever),能夠克服PSD內固有的系統雜訊(Noise),以及環境雜散光(Stray light)的影響,成功的提升光學偵測系統的靈敏度。另外,當我們固定微球面反射鏡的曲率半徑時,增加入射角度也能夠放大光偏折位移。這也意謂著我們可以藉由改變入射角度來動態調整光學偵測系統的靈敏度。 在本論文中,我們將MSRM-integrated cantilever應用在表面張力與濃度的量測上。在實驗的過程中,MSRM-integrated cantilever會架設於靜置的水珠(氯化鈉溶液或酒精水混合液)的上方,而乘載水珠的玻璃基板,由精密的移動平移台緩慢地抬升,一旦懸臂樑的底部碰觸到水珠表面時,水珠會瞬間形變且懸臂樑會因為表面張力的緣故,受到一個向下的拉力而偏折彎曲。此時懸臂樑的偏折量會與水的表面張力有關,而水的表面張力會受到氯化鈉的莫耳濃度所影響。根據我們的實驗,水的表面張力會從72.1 mN/m增加到77.7 mN/m,當氯化鈉的莫耳濃度從0 M提高到3.13 M。同時,我們也驗證有機溶質會降低水表面張力的現象,例如:乙醇水混合液(Alcohol-water mixture)。當乙醇的莫耳濃度從0 M增加至0.81 M時,它的表面張力從71.4 mN/m降到57.5 mN/m。

並列摘要


By fabricating a micro spherical reflecting mirror (MSRM) on the tip of a cantilever, the deflection angle of the laser beam is significantly magnified. Therefore, the sensitivity of an optical sensing system is enhanced. The curvature of the spherical reflecting mirror determines the system sensitivity. Given a certain bending amount and a fixed distance between the cantilever and the position-sensing detector (PSD), the cantilever combined with a MSRM with a smaller radius of curvature produces a larger optical deflection, i.e. better system sensitivity. Also, under a given radius of curvature of the MSRM, the system sensitivity can be adjusted by changing the incident angle. A larger incident angle exhibits better system sensitivity/responsivity. In this paper, it is employed as a surface tension and concentration gauge that only requires of solution. The MSRM-integrated cantilever is first set above a sodium chloride–water droplet carried by a glass substrate, and then the droplet is moved up gradually. Once the cantilever is touched by the droplet, it is pulled and bent down as the droplet reshapes. The cantilever deformation amount is related to the surface tension of the solution, which increases with the molar concentration of sodium chloride. According to our experiments, the surface tension varies from 72.1 mN/m to 77.7 mN/m as the molar concentration of sodium chloride in water increases from 0 M to 3.13 M. Therefore, by measuring the bending amount of the cantilever, the surface tension as well as the concentration of the NaCl-water solution can be determined. We also perform the experiments on the alcohol (ethanol)-water mixture, whose surface tension, conversely, reduces from 71.4 mN/m to 57.5 mN/m as the alcohol molar concentration increases from 0 M to 0.81 M.

參考文獻


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