Multi-scaled Super-hydrophobic Surface Structure Combined with Anti-reflective Effect
Date Issued
2006
Date
2006
Author(s)
Mei, Guang-Hua
DOI
en-US
Abstract
Lotus leaf with super-hydrophobic effect, i.e., the contact angle larger than 140 , was well known and had been studied extensively in the last decade. This thesis proposed a multi-scale grating that is composed by sub-wavelength and micron-scaled surface structures. Such type of structure is quite similar to that of the lotus leaf except that the arrangement in this surface is regular and not as random as that of the lotus leaves. Anti-reflection effect combined with self-cleaning effect is theoretically predicted to be a fundamental characteristics of such surface structure.
The optical behavior of the multi-scaled gratings is simulated by rigorous coupled wave analysis (RCWA). For simulation, an equivalent model derived from the effective medium theory was introduced to simplify the calculations for sub-wavelength gratings. Contact angle estimation was achieved by using Wenzel’s formula and Cassie’s formula.
Electron bean lithography was used to fabricate the sub-wavelength structure. Optical lithography was adopted to obtain micron-scaled surface structures. Patterns were transferred to silicon substrate by inductive coupled plasma (ICP) etching technique once the mask was done by the previous two methods. Comparing the theoretical simulation and experimental verification, it is verified that the anti-reflection effect exists when the sub-wavelength grating is fabricated on the micron-scaled grating. However, the water droplet sliding was hinder by the hysteresis induced by the geometric specimens, which prevents the droplet from sliding freely. It is thus suggested that more investigations on the self-cleaning effect induced by the multi-scale grating must be done in order to further advance the knowledge in this ever more important field.
Subjects
抗反射
超疏水
蓮花效應
光柵
次波長
複合尺度
遲滯現象
Anti-reflective
Super-hydrophobic
Lotus-effect
Grating
Sub-wavelength
Multi-scale
Hysteresis
Type
thesis
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