| 摘要: | 液滴或氣泡常出現於日常生活與自然界中，其在材料表面的運動涉及複雜的氣/液/固三相的交互 作用，常在流體運動行為中扮演關鍵角色。各種工業與民生應用常需要具備不同類型潤濕特性的表面， 而材料表面經過適當的改質可呈現出特殊的表面潤濕行為，具有高應用價值。舉例而言，超親水表面 可應用於抗霧、抗反射、及抗生物沾黏等領域；而超疏水表面則具有表面自清潔的功能及可降低物質 輸送過程能量損耗的潛力。由於表面潤濕性質亦取決於氣/液/固三相的界面能，所以液滴或氣泡的運 動與表面潤濕性質密切相關。透過研究液滴或氣泡在具特殊潤濕性質表面的運動，可解決工業產品在 輸送現象上遭遇的困難，例如微流道與注射系統中的氣泡柱塞等問題，或協助發展液滴型態的微流道。 本計畫為期三年，結合理論模擬與實驗深入探討超疏水與超親水表面的氣泡與液滴運動。 計畫第一年，將合成具穩定性的超疏水與超親水表面。目前超疏水表面於水中在短時間內即失去 功能；同樣地，超親水表面可透過簡單的火焰燒噴玻璃而獲得，但在空氣中靜置短時間也會失去其完 全潤濕的特性。為能研究氣泡在水中沿著超疏水表面的運動行為，必須製備出可長時間靜置於水中仍 保持性質穩定的表面。同樣地，為能研究液滴在空氣中沿著超親水表面的運動行為，也必須製備出可 長時間靜置於空氣中仍保持性質穩定的表面。計畫第二、三年則同時進行滑動實驗與理論模擬。由於 氣/液/固三相的流動涉及接觸線的移動，其模擬計算一直是個挑戰。本計畫將以多體耗散粒子動力學 模擬氣泡或液滴的運動行為，並與實驗的結果相互比較。研究成果將可幫助學者了解氣泡或液滴運動 和表面潤濕性之間的關聯性，並得到超疏水與超親水表面對流體運動的摩擦機制。 ;Drops and bubbles, such as rain drops and gas bubbles in aerated drinks, are often present in our daily life and nature. Their motions along the material surfaces involve the interactions among three phases (gas/liquid/solid) and play an important role in fluid transport. Owing to numerous scientific and industrial applications involving fluid/substrate interfaces, the material surfaces with various types of wettability are needed. After suitable surface modifications, substrates can show specific wetting behavior and possess highvalue applications. For instance, superhydrophilic surfaces can be used for anti-fog, anti-reflection, and antibiofouling fields; in contrast, superhydrophobic surfaces possess the self-cleaning ability and have the potential to be utilized for reducing energy consumption during mass transport. Because the wettability depends on the interfacial tensions among g/l/s three phases, the motion of drops and bubbles is closely related to the wettability. The difficulties of industrial processes and the products encountered in the transport phenomena, such as the bubble plunger in micro-fluidic systems and syringe devices, can be resolved by studying the motion of drops and bubbles. In this three-year project, the contact line motion of drops and bubbles along superhydrophobic or superhydrophilic surfaces will be investigated both experimentally and theoretically. At the first year, stable superhydrophilic and superhydrophobic surfaces will be fabricated. Till now, the synthesized superhydrophobic surfaces lose their superhydrophobicity after immersed in water for a short period of time. Similarly, superhydrophilic surfaces fabricated by simply burning the glass slices lose their total wetting property when kept in ambient air for a while. In order to explore the bubble motion beneath the superhydrophobic surface submerged under water, the superhydrophobic surface with long-term underwater stability has to be fabricated. Likewise, to investigate the drop motion along the superhydrophilic surface in air, the superhydrophilic surface with long-standing stability in ambient air needs to be synthesized. During the second and third years, the sliding experiments and theoretical simulations will be conducted simultaneously. Since the g/l/s three-phase flow involves the contact line motion, its microscopic simulation without resorting to any assumption is a challenging task. In this project, the motion of bubbles and drops will be simulated by many-body dissipative particle dynamics and the simulation outcomes will be compared with our experimental results. The research results will help us to understand the peculiar behavior of the motion of drops and bubbles on surfaces with extreme wettability. Furthermore, the findings will also assist in acquiring the friction mechanism of superhydrophobic and superhydrophilic surfaces on fluid motion. |
