材料表面潤濕性對提升大氣露水收集效率之研究

Abstract

本論文提出一種藉由CO2雷射快速生成超疏水表面，再利用445nm藍光二極雷射在原先的超疏水層上有選擇性的生成出超親水表面，藉此技術能有效率地獲得超親水與超疏水混合表面，我們發現藉由調整445nm藍光二極雷射參數以及掃描方向可以獲得不同浸潤型態得超親水表面。探討大氣冷凝露水收集方面我們比較了4種表面分別為超親水表面、超疏水表面以及兩種混合表面在低過冷環境以及高過冷環境條件下的收集效率，我們透過攝影機記錄了每個樣本在5個小時中的露水收集過程，我們分析了不同表面大氣露水收集過程中液滴收首次掉落以及平均掉落的時間，可以發現設計過的超親水超疏水混合表面擁有較好的排水效率因此其液滴首次掉落以及平均掉落效率都比超親水表面來的好，在高過冷環境中，露水成核速度更快這使得與低過冷相比有更快液滴掉落速率，此外我們還發現在兩種環境下混合表面相較於超親水與超疏水表面都有較好的收集效率。 接下來為了提升露水收集效率，我們提出了自潤滑表面作為新型的大氣冷凝露水收集策略。我們比較了7種自潤滑表面，分別為光滑PDMS、光滑PDMS-矽油複合材料、不同目數的砂紙（40、240、600、1000）以及霧面壓克力板，這些表面包括了5種不同結構大小的PDMS-矽油複合材料。我們在冷凝露水成核的初期發現，液滴能夠藉由自潤滑材料表面的特性自主滑落，並且在滑落後帶走一排液滴，使空出的表面能夠繼續成核露水。這樣的策略可能達到理想的高頻率刷新與集水效果。我們探討了光滑表面與結構型自潤滑表面對冷凝露水收集效果的差異。最終我們發現，當自潤滑表面的結構過大時，表面的自潤滑效果會減弱，取而代之的是結構帶來的高滯後現象，這會導致露水收集效率降低。最終，我們發現在具有微小結構的翻模目數1000砂紙和霧面壓克力PDMS-矽油複合材料，由於其微小結構的特殊潤滑行為，有效避免了高滯後現象並提供了成核點位，因此達到了有效的集水與排水效果。這兩者在大氣露水收集過程中擁有最佳的露水收集效率。

The thesis proposes a method for rapidly generating a superhydrophobic surface using CO2 laser, followed by selectively fabricating a superhydrophilic surface on the initial superhydrophobic layer with a 445 nm blue diode laser. This technique enables the efficient fabrication of a hybrid surface with both superhydrophilic and superhydrophobic properties. We found that by adjusting the parameters of the 445 nm blue diode laser and the scanning direction, we can obtain superhydrophilic surfaces with different wettability patterns.

In the study of atmospheric dew collection, we compared four types of surfaces: superhydrophilic surfaces, superhydrophobic surfaces, and two types of hybrid surfaces with both superhydrophilic and superhydrophobic properties under conditions of low and high subcooling. We recorded the dew collection process of each sample over five hours using a camera, analyzing the time of the first droplet fall and the interval between droplet falls during the dew collection process for different surfaces. The results show that the designed superhydrophilic-superhydrophobic hybrid surfaces have better drainage efficiency, leading to a faster first droplet fall and shorter intervals between droplet falls compared to superhydrophilic surfaces. Moreover, in highly subcooled environments, the extreme conditions result in a faster nucleation rate of dew, leading to a quicker droplet fall rate compared to low subcooling environments. Additionally, we found that mixed surfaces had better collection efficiency compared to superhydrophilic and superhydrophobic surfaces in both environments.

To enhance dew collection efficiency, we proposed self-lubricating surfaces as a novel strategy for atmospheric condensation water collection. We compared seven types of self-lubricating surfaces: smooth PDMS, smooth PDMS-silicone oil composites, sandpapers with different grits (40, 240, 600, 1000), and matte acrylic plates, including five different structural sizes of PDMS-silicone oil composites. We observed that, during the early stage of condensation, droplets could autonomously slide off due to the properties of the self-lubricating materials, carrying away a line of droplets and allowing the exposed surface to continue nucleating water. This strategy could achieve an ideal high frequency of refresh and water collection. We explored the differences in condensation water collection efficiency between smooth surfaces and structurally self-lubricating surfaces. Ultimately, we found that when the structure of the self-lubricating surface was too large, the lubricating effect weakened, replaced by a high hysteresis phenomenon, which reduced dew collection efficiency. We discovered that sandpaper with a grit size of 1000 and matte acrylic PDMS-silicone oil composites, with their unique lubricating behavior due to fine structures, effectively avoided high hysteresis and provided nucleation sites, resulting in efficient water collection and drainage. Both of these demonstrated optimal dew collection efficiency in atmospheric dew collection.