本論文的動機是日常生活常見的墨汁在水中散佈的現象：當墨汁液滴落入水中時，我們不只觀察到了日常生活中常見的墨汁在水中迅速暈開擴展現象，更是發現了在液面下方中心形成一奇特細絲現象。但實際上在本論文中我發現奇特細絲現象也能透過液滴輕觸液面以及球珠表面沾附墨汁落入溶液中的方法所觀察到，因此本研究將針對低雷諾數的條件下去探討使用兩種方法所形成奇特細絲現象及其應用。
液滴輕觸液面的方法中(請參照第三章和第四章)，發現高雷諾數以及低雷諾數條件下所形成的奇特細絲現象不大相同。在高雷諾數(Re為102)的條件下，奇特細絲現象是由一蘑菇狀的Crown尾端所帶出來的，然而細絲只能維持一小段時間，蘑菇狀的Crown即迅速的發生破裂(breakup)現象，使得我們再無法觀察到奇特細絲的形成。而低雷諾數(Re為10-3)條件下，黏度較高的溶液可以使液滴的型態趨於穩定，使得液滴以一液滴狀落下，從而形成一平直且長的細絲而不會破裂。因此為了瞭解細絲是否為液滴的一部分，特別針對液滴在包括細絲阻力時的落下速度進行測量，並與Stokes’ terminal velocity進行比較，發現前者的落下速度比後者來的慢，而Stokes’ terminal velocity對於液滴是屬於最慢的速度，這也意味著必定有其他因素參與其中。我發現主要的因素為液滴內部渦環(Vortex ring)的作用所引起的流體夾帶(Fluid entrainment)效應，使得液滴整體密度降低，進而造成液滴驅動力降低，另外，我也使用弗林試劑(Ferroin solution)來測試液滴中的墨汁粒子是否會對液滴的落下過程產生阻力，並再次發現液滴在包含細絲阻力下落下速度仍然比Stokes’ velocity來的慢，這也表明了墨汁顏料不會對液滴有一阻力的影響。儘管如此，為了觀察細絲可以延伸至多長，我在高度較高的容器中進行液滴輕觸液面實驗，發現液滴的型態最終還是會發生破裂進而終止了細絲的延伸。另外，細絲的上半部已呈現變形的狀態，這意味著三件事，第一是細絲並非由液面上方的墨汁注入所形成，第二是整體細絲是不受表面張力所作用的，第三是細絲是由液滴尾端持續洩漏所形成。
為了進一步延伸細絲的長度，我透過球珠表面沾附墨汁落入溶液中來進行實驗(請參照第五章)。我們觀察到一連續的細絲形成且並未發生破裂，細絲的形成似乎是由球珠的尾端所形成。為了得知細絲是如何形成的，我們將墨汁塗抹於球珠的下半部並落入溶液中，結果發現球珠下半部的墨汁會經由外部溶液的掃掠至球珠尾端而洩漏形成細絲，這也更證明了細絲是由鋼珠所帶出來的。此外，我也發現只要能夠確保球珠持續的在高容器中落下以及球珠表面具有足夠的墨汁，即可使細絲不斷的延伸而不中斷，長度甚至可長達1公尺。
為了能夠使奇特細絲有更進一步的應用，我發明了一種由高分子溶液取代墨汁來製備微纖維的簡單新方法(請參照第六章)。通過聚合物鏈之間的交聯反應(Cross-linking reaction)使細絲硬化，使細絲製備成微纖維，而此方法的優點在於可以透過不同大小的實心球體去控制微纖維的長度與直徑，透過此方法所形成的微纖維長度為1至4公分，直徑為200至300?m。儘管成功率較低，但透過液滴輕觸液面方法可以製備更細的微纖維(直徑約為60?m)。與常見的方法不同，例如：電紡絲以及擠出，此方法並不需要任何額外的力場即可製備微纖維。
本論文所發現的奇特細絲的形成以及相關應用不僅為低雷諾數條件下的部分互溶的流體動力學提供了全新的面向，並且提供了以流體力學的方式製備微纖維的新方法。

1.SUMMARY
In this thesis, we are motivated by the commonly observed ink spreading phenomenon: when an ink drop falls into a deep liquid pool, it rapidly spreads into a plume with an immediate formation of a thin thread at the center of the liquid surface upon the impact. In this thesis, I discover that a peculiar thin thread can also form when gently placing an ink drop onto the liquid surface. Such a thin thread can also be observed during the falling process of an ink-painted solid sphere when it is gently placed on the liquid surface. This thesis is to explore the formation of a thin thread and its application using these two approaches under the low Reynolds number condition. However, the thin thread formed by gently placing a drop onto the liquid surface approach and placing a painted solid sphere on the liquid surface approach are virtual. We can't take it out of the solution, so I develop a new and simple approach to prepare a microfiber using a polymer solution. By means of a cross-linking reaction between polymer chains, I am able to harden the filament, turning it into a microfiber. This approach offers the advantage that such a microfiber can be made tunable by using different sizes of solid spheres. Although the drop gently touching the liquid surface to prepare the microfibers is often failing, but the microfiber's diameter is the smallest. The diameter of the microfibers is 40µm.

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