Design and Preliminary Fabrication of Nanostructured Surface for Anti-reflective and Hydrophobic Effect
Date Issued
2004
Date
2004
Author(s)
Chang, You-Chia
DOI
en-US
Abstract
Some structured surfaces such as lotus leaves show very special wettability behavior. They are called super-hydrophobic surfaces since the contact angles exceed 140 degree. Most attractive property of super-hydrophobic surface is the self-cleaning effect. On the other hand, there is another group of structured surfaces which shows antireflective (AR) effect. For this kind of surfaces, the structure is periodic and at subwavelength scale.
In this thesis, we propose a new idea – the AR and super-hydrophobic effects can be combined together since they both attribute to the existence of surface structure. The combination can produce new applications. For example, a “self-cleaning” AR surface can be used on solar cells to improve efficiency. A “transparent” super-hydrophobic surface can be made on windshields or windows.
From the knowledge of subwavelength optics and wettability, we conclude that the combination is possible by imparting a periodic subwavelength structure with continuous profile to an intrinsically hydrophobic material. The AR behavior is analyzed by effective medium theory (EMT) and rigorous coupled-wave approach (RCWA). The wettability is analyzed by minimizing the total surface energy.
We fabricate desired structured surfaces by holographic lithography, plasma etching and Teflon coating. The performance is evaluated by measuring the reflectance spectrum and contact angle. For the 1D structure fabricated in this thesis, the measured reflectance spectrum matches the simulation. Although super-hydrophobic effect is not observed on regular 1D structure, it is observed super-hydrophobicity on over-etched irregular 1D structure. We conclude from experimental results that 1D structure is not suitable for the combination of AR and super-hydrophobic effects. The experiment indicates the combination is very promising by proper 2D structures.
Subjects
抗反射
超疏水表面
蓮花效應
次波長結構
lotus effect
subwavelength structure
super-hydrophobic surface
antireflection
Type
thesis
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