臺灣大學: 化學工程學研究所諶玉真朱彥旭Chu, Yen-HsuYen-HsuChu2013-03-272018-06-282013-03-272018-06-282011http://ntur.lib.ntu.edu.tw//handle/246246/252207在日常生活中，我們時常可以觀察到液滴於不同幾何形狀之表面的潤濕現象。在理想的平坦表面上，液滴的潤濕行為可藉由Young’s方程式來描述，就已知文獻資料來看，液滴於平坦表面之潤濕行為已廣泛被研究。隨著合成與加工技術不斷進步，微奈米材料的表面圖案與塊狀形狀(如圓柱狀)，在工業界應用及科學研究中經常被探討，改變表面與整體形狀對於液滴潤濕行為的影響是界面科學的重要議題，故本篇研究目的在於探討液滴於圓柱狀纖維的潤濕行為，且將以液滴形狀、體積與表面接觸角等因子來描述並建立對應的相圖，在液滴於圓柱體表面潤濕的系統中，液滴的形狀可以分成兩種：形狀為軸對稱的barrel以及不對稱的clam-shell。本研究以熱力學能量最小化法的概念，藉由數值軟體(Surface Evolver)探討圓柱體上的潤濕行為，此外，我們也將模擬與實際實驗的結果做比對。首先，我們研究液滴於水平纖維上在有重力條件下的潤濕行為，以及探討纖維粗細度對潤濕行為的影響，比對過去文獻與本研究的結果可知，該相圖的資訊在定性與定量上有良好的描述與一致性。我們也探討在有重力條件下，垂直纖維上液滴的潤濕行為。我們將研究分為兩種不同的系統來探討：在垂直纖維的底部設置超疏水板以及將垂直纖維設定有兩種不同的親疏水性(上半部較為親水，下半部則疏水)。我們發現液滴體積較小及接觸角較大時，液滴會趨向以clam-shell的形態存在，另一方面，當液滴體積較大及接觸角小時，barrel形態的液滴較容易存在。此外，在某些情況下(液滴體積及接觸角)，會有不只一種型態的液滴穩定存在，即共存區。我們也就纖維的粗細度對液滴潤濕行為的影響做深入地探究，從相圖看來，半徑較粗的纖維相較於細纖維，因為受到重力效應的影響較大，所以在半徑較粗纖維的相圖中，兩種形態液滴的共存區會縮小。經由與實際實驗比對我們可以發現，本研究的模擬結果與實驗上有良好的一致性。Droplet-on-fiber is commonly observed in our daily life and is closely related to dyeing fabrics and fiber-based microfluidic devices. The wetting behavior of droplet-on-fiber is different from that of drop-on-plane due to the global cylindrical shape, however, the systems of droplet-on-fiber are more complicated and therefore are less studied. A combined numerical simulation and experimental observation were conducted to investigate the equilibrium shape of a droplet on a fiber. In this work, the energy calculation was accurately performed by using a powerful modeling tool, the Surface Evolver, which is based on the finite-element simulation. The phase diagram of droplet-on-fiber is also established by using SE. The droplet-on-fiber systems are studied in three parts. First, we simulated the droplets on a horizontal fiber in the presence of gravity. Our results show that the fiber diameter affects the size of the coexistent regime greatly. Then, we conducted a simulation of droplets on a vertical fiber with a superhydrophobic plane. From the simulation results and the experimental observations, we found that the clam-shell configuration appears for small volume and large contact angle, while the barrel shape is formed for large volume and small contact angle. In the third part, we divided the vertical fiber into two sections: the upper section is hydrophilic while the lower section is hydrophobic. The agreement of the droplet shape between the SE simulations and experimental observations are quite well. We also found that both barrel and clam-shell configurations can coexist in certain conditions and thus indentified the existence of the muiltiple stable states. There are four regimes in the phase diagram, including (I) clam-shell only, (II) coexistence of barrel and clam-shell, (III) barrel only, and (IV) falling-off in the shapes of clam-shell. Moreover, due to the gravitational effect, the upper boundary of barrel only regime shifts downward, and the domain of the coexistent regime shrinks when increasing the fiber diameter.3248229 bytesapplication/pdfen-US液滴垂直纖維電腦模擬dropletvertical fiberSurface Evolverthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/252207/1/ntu-100-R98524071-1.pdf