自1970年Athur Ashkin等人第一次使用雷射光捕捉到微小粒子後，雷射光鉗(optical tweezers)便不斷開始發展與演進。至今，由雷射光組成的雷射光鉗已經在生物以及物理領域中成為常見以及時常被應用的技術。
褐藻醣膠(fucoidan)是一種多醣，主要是由褐藻中所提煉出來，由於它多樣的生物特性，包括抗凝血和抗血栓、抗病毒、抗腫瘤和免疫調節，因此雖然目前被歸類於健康食品卻有相當高的醫療潛力，也因此褐藻醣膠在近幾年來被廣泛的研究著。
本研究利用雷射光鉗系統，結合了擁有高位移解析度的壓電平台，應用於測量褐藻醣膠在不同濃度、不同PH值、不同溫度的黏彈性和剪力模數(complex shear modulus)。實驗中利用PBS緩衝液將褐藻醣膠配成不同濃度的溶液並配製成不同pH值的溶液和加入不同添加物，接著使用雷射光捕捉聚苯乙烯微球測量微球在溶液中的熱擾動(thermal motion)變化，並研究褐藻醣膠溶液在不同情況下的黏度變化和流變性。
本實驗首先量測純水溶液藉以計算得到電壓-位移轉換因子β (voltage-displacement coefficient)，和實驗所需的雷射光鉗彈性係數(trap stiffness)。本實驗利用固定微球法以及以能量頻譜值為基礎來計算的方式求得β值，彈性係數的量測則分別使用能量頻譜值(power spectral density)能量均分定理(equipartition)及波茲曼分佈(Boltzman distribution)來分析。接著量測褐藻醣膠在不同情況下黏度和黏彈模數的變化。
實驗中利用雷射光鉗與微流變學結合的方式研究褐藻醣膠的特性。相對於過去傳統流變儀的量測方法，使用雷射光鉗和微流變學結合的方式能夠擴大採樣頻率的範圍，而且也有減少了實驗耗材的成本等優點。在研究發現褐藻醣膠容易溶於水中，隨著濃度越高溶液的黏度也越大。過高的溫度則會破壞褐藻醣膠的氫鍵和分子間的交聯，在七十度以上時則結構完全被破壞。此外我們也發現在中性時褐藻醣膠的結構較穩定，但是在酸性或鹼性狀態下容易水解或是有異構化的反應發生。在加入鹽類的情況下由於離子間靜電作用力的影響會造成黏度和彈度的下降。
本研究在不同環境與不同添加物下去研究褐藻醣膠的特性，希望未來可以應用在食品科學或是生化的研究上。

It was 1970 that Arthur Ashkin first succeeded to trap and manipulate particles by using optical tweezers. Since then, optical tweezers start to be developed and improved. Up to now, optical tweezers which are made of lasers are already become one of the most applied technology in the field of biology and physics.
Fucoidan is a polysaccharide, and it’s mainly refined from the brown alga. Due to its various characteristics, including anticoagulant and antithrombotic, antivirus, antitumor and immunomodulatory, though it is classify as healthy food so far, it has a high potential for medical, that’s the reason why the fucoidan has been extensively studied for decades.
In this research, we used an optical tweezers system combined with a piezoelectric platform which has a high displacement resolution, and applied them to measure the viscoelasticity and complex shear modulus of the fucoidan in different concentration, pH value, and temperature. The fucoidan solutions were made in different concentrations (i.e. by blending the fucoidan and PBS buffer together) at different pH value (i.e. by adding acetic acid and sodium hydroxide,) and adding in different additives. We proceeded using the optical tweezers to catch the polystyrene microsphere, and measure the thermal motion of it in the solution, and then we calculated the viscosity changing and the rheology of the fucoidan solution under
different conditions.
We investigated the characteristics of fucoidan using optical tweezers based on the microrheology in this experiment. In contrary to the traditional measure by rheometer, our investigation can expand the range of sampling frequency and decrease the cost of experimental consumables. After the investigation, we concluded that the higher the concentration goes, the larger the viscosity is. High temperature could break the hydrogen bond and the connection between molecules of fucoidans , when the temperature is above 70 degrees, the structure become totally damaged. The structure of fucoidans is more stable in neutral pH, however in other pH′s, fucoidans are easily hydrolyzed or isomerized. If saline is added to the solution, viscosity and elasticity get lower due to the electrostatic interactions between the ions. In this research, we studied the characteristics of the fucoidan under different conditions and with different chemical additives. The investigations have the potential apply to the research of the bromatology or biochemistry.

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