梯度奈米結構製備與奈米結構於氣泡捕捉與排氣之應用

Abstract

本論文第一部份將介紹以簡單製程技術製備梯度濕潤性奈米結構表面:利用金屬催化化學蝕刻製程藉由氧化還原反應的機制製備矽奈米結構表面，因此隨著蝕刻時間不同，不同密度分布的奈米結構可於同一表面上被表現。藉由掃描式電子顯微鏡所拍攝的影像與影像分析軟體Image J與數值分析法的觀察與實驗結果得知在同一表面上隨著觀察的位置距離增加(蝕刻時間增加)，奈米結構的密度也隨之遞減。接著藉由接觸角的量測實驗得知在一連續位置的奈米結構表面上液珠具有不同的接觸角且呈現遞增的趨勢。再者，藉由影像處理中每一分析位置點的奈米結構圖所得到的面積碎度與所量測的接觸角趨勢做比較可得知表面潤濕性與表面型態具相關性:表面疏水性隨著表面碎度減少而增加，且存在著適當的表面型態以呈現最佳的疏水性。最後藉由Cassie-Baxter特性來討論實際液珠在結構上的潤濕情形，由結果可得知奈米結構的型態將影響實際液珠的表現特性。 論文第二部份將探討矽奈米結構於氣泡捕捉與排氣之應用。首先將觀察不同表面型態對氣泡的捕捉能力，由實驗結果得知氣泡容易貼附於奈米結構表面且不易脫離。接著，利用氫氧化鉀蝕刻技術在矽晶片上製作凹槽開孔作為排氣孔，並比較平滑表面與奈米結構表面之排氣孔的排氣效能。實驗結果顯示在兩種不同排氣孔表面的晶片上，氣泡會出現一般情形:氣泡成長至適當大小並與排氣孔斜角接觸，氣泡被捕捉於排氣孔側壁，在排氣孔側壁與其他氣泡結合至氣泡大小與排氣端接觸，最後進行排氣步驟。藉由量化單科氣泡的排氣過程可發現具奈米結構的排氣孔可提供氣泡貼附點，促使氣泡更容易被捕捉於排氣孔進而縮短排氣過程的時間。 藉由以上實驗結果顯示，本論文提供一簡單製程技術成功製備具梯度濕潤性之奈米結構，藉由梯度濕潤性的特性，此表面將可利用於微流體系統與基本生物研究領域。另外藉由奈米結構於氣泡之捕捉與排氣之研究，具奈米結構之排氣孔可有效促進排氣過程，此特性除可以用於基本生物研究外也可應用於燃料電池中以提升能量效能的運用。

This thesis first studied the fabrication of gradient wettability nanostructure surface. The nanostructure surface was fabricated by using Ag-assisted chemical etching process; meanwhile, based on the mechenism of redox reaction of etching process, the nanostructures with different morphologies on a chip would be prepared. the distribution of nanostructure was decreased along continuous positions on a chip that have been observed and investigated from series SEM images and different image process. Therefore, the wettablity of the nanaostructure was examined and the results were indicated that the contact angle was varied along the continuous positions from 90 degree to 130 degree in a distace of 18mm. The wettability was varied with the distribution of nanostructure have been shown by comparing the area fraction of nanostructure which analyzed by Image J and math counting and contact angle of water droplet at investigated positions; moreover, the wetting behavior of droplet on nanostructure was investigated by using Cassie-Baxter regime. After all, the gradient wettability nanostructure surface on a chip have been sucessively fabricated. The second part of thesis futer introduced silicon nanostructures on bubble trapping and degassing. First, the bubble trapping capabillity at different surfaces was examined and the reslts were indicated that the chemically generated bubbles could be easily trapped on heterogeneous nanostructure surface; moreover, bubble easily nucleated on the nanostructure surface also been observed. Secondly, A silicon chip which was executed with KOH etching process to produce concave holes have been introduced to the degassing test; moreover, the effects of two different morphologies of degassing holes include smooth and nanostructure surface would be investigated. Generally, in both of different type of degassing chip the behavior of generated bubbles would grow, aggregate with other bubbles, and be transported and trapped into the degassing hole, and then be degassing. moreover, the results were indecated that because the nanostrucure surface provide bubble perferable locations to attach, the degassing holes with nanostructure surface would advance the bubble trapping process and degassing process. Based on the results of experiments, the gradient wettability nanostructure surface has potential to apply in microfluidic systems and fundamental biological investigations; on the other hand, the nanostructured degassing chip could be used not oly for biological applications, but also for advancing the power efficiency of methanol fuel cells.