微纳米结构超疏水表面制备和减阻机理研究
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微纳米结构超疏水表面制备和减 阻机理研究
(申请清华大学工学硕士学位论文)
培 养 单 位 ： 航天航空学院
学
பைடு நூலகம்
科 ：力 学
研 究 生 ：卢 思
指 导 教 师 : 姚朝晖 副教授
二○一二年五月
Fabrication and drag reduction mechanism of super-hydrophobic surfaces with micro-nano structures
Thesis Submitted to Tsinghua University in partial fulfillment of the requirement
for the degree of Master of Science
in Mechanics
by Lu Si Thesis Supervisor : Associate Professor Yao Zhaohui
May, 2012
摘要
摘要
超疏水表面的优异性质使其在现代生活和工业生产中具有十分广泛的应用。 超疏水表面具有很好的自清洁效应。液体在超疏水表面附近流动的时候会产生壁 面速度滑移。这一性质与普通流动中的壁面无滑移条件是不同的。 在一些微米级 特征长度的流动中，已经有人观察到了速度的滑移。最近的研究中，人们发现在 由超疏水表面构成的槽道中，流动的阻力比普通槽道中的流动阻力小，即存在流 动减阻效应。
本文还利用 Micro-PIV 技术与 PIV 技术测量了具有超疏水表面的槽道内的速 度场，分析了速度脉动量对于流动减阻的影响，并与普通表面附近的流场速度进 行比较。在层流情况下，超疏水表面附近的速度脉动量与普通表面附近的速度脉 动量相近，两者由速度脉动造成的动量输运产生的雷诺应力相近。因此层流情况 下，超疏水表面减阻的主要原因是因为微细结构之间的气液界面减小粘性应力。 而在湍流情况下，超疏水表面能够同时减小粘性应力和雷诺应力，使得湍流减阻 效果更加显著。
Currently, most researchers in this field believe that there are mainly two conditions for the formation of super-hydrophobic surfaces. The first condition is the existence of a layer of hydrophobic material on the surface, which can reduce the surface energy. The second condition is the existence of micro and nano structures on the surface. Today there are a lot of methods which could prepare super-hydrophobic surfaces with these two conditions. Chemical vapor deposition, chemical etching, sol-gel method and photolithography, are often used to prepare super-hydrophobic surfaces. Although there are many researches related to the drag reduction on super-hydrophobic surfaces, there is not yet a clear explanation and conclusion about the mechanism. Many researchers have already observed the drag reduction in laminar flow on super-hydrophobic surfaces. However, there are only a few researches which focus on drag reduction in turbulent flow. In addition, most of the super-hydrophobic surfaces using in these experiments only have one-scale micro structures on the surfaces. Super-hydrophobic surfaces, which are more familiar with real lotus leaves, with dual-scale mirco-nano structures are seldom prepared and used in experiments.
本文采用了两种全新的方法制备了具有二级微纳米结构的超疏水表面。测量 了由超疏水表面构建的槽道中的流动压差，将其与普通表面构建的槽道内的流动 压差进行比较，发现在层流情况下，流动阻力减小最多达到了 36.3%。在湍流的情 况下，超疏水表面的减阻比例约为 53.3%，减阻效果比层流更加明显。
在层流下超疏水表面减阻效应的探究性实验中，我们证实层流情况下，超疏 水表面减阻的主要原因是因为微细结构之间的气液界面的存在减小了粘性应力。
关键词：超疏水表面；减阻；二级微纳米复合结构；表面制备
I
Abstract
Abstract
Super-hydrophobic surfaces have been widely applied in modern life and industrial production because of their excellent properties. Super-hydrophobic surfaces have a self-cleaning property. On super-hydrophobic surfaces, liquid could keep as a droplet and easily scroll through the surfaces. In a liquid flow in a channel covered with super-hydrophobic surfaces, there is a significant velocity slip near the wall of the surfaces, which is different from the situation of flows on normal surfaces. In the flow with a micro-level characteristic length, researchers have already observed the slip of the velocity. In recent studies, it was found that the flow drag on super-hydrophobic surfaces is smaller than that on normal surfaces, that is, there is a flow drag reduction on super-hydrophobic surfaces.
目前，学者们认为超疏水表面形成的条件主要有两点，一是表面具有较低的 表面能，二是表面具有微纳结构。目前能够达到这两个条件而制备出超疏水表面 的方法有很多。比如常用的光刻法、化学沉积法，化学刻蚀法以及溶胶凝胶法等 等。对于超疏水表面存在的流动减阻效应，虽然目前已经有一定的研究，但研究 者们对于超疏水表面流动减阻的机理还没有很明确的定论。已经有很多学者在层 流流动中观测到了超疏水表面的流动减阻。然而针对湍流流动中超疏水表面的流 动减阻的研究还相对较少。另外，大部分用于实验的表面都是由只有一级微米结 构构成的表面。针对更接近真实荷叶表面的具有二级微纳米复合结构的表面的流 动阻力特性的研究也相对较少。
(申请清华大学工学硕士学位论文)
培 养 单 位 ： 航天航空学院
学
பைடு நூலகம்
科 ：力 学
研 究 生 ：卢 思
指 导 教 师 : 姚朝晖 副教授
二○一二年五月
Fabrication and drag reduction mechanism of super-hydrophobic surfaces with micro-nano structures
Thesis Submitted to Tsinghua University in partial fulfillment of the requirement
for the degree of Master of Science
in Mechanics
by Lu Si Thesis Supervisor : Associate Professor Yao Zhaohui
May, 2012
摘要
摘要
超疏水表面的优异性质使其在现代生活和工业生产中具有十分广泛的应用。 超疏水表面具有很好的自清洁效应。液体在超疏水表面附近流动的时候会产生壁 面速度滑移。这一性质与普通流动中的壁面无滑移条件是不同的。 在一些微米级 特征长度的流动中，已经有人观察到了速度的滑移。最近的研究中，人们发现在 由超疏水表面构成的槽道中，流动的阻力比普通槽道中的流动阻力小，即存在流 动减阻效应。
本文还利用 Micro-PIV 技术与 PIV 技术测量了具有超疏水表面的槽道内的速 度场，分析了速度脉动量对于流动减阻的影响，并与普通表面附近的流场速度进 行比较。在层流情况下，超疏水表面附近的速度脉动量与普通表面附近的速度脉 动量相近，两者由速度脉动造成的动量输运产生的雷诺应力相近。因此层流情况 下，超疏水表面减阻的主要原因是因为微细结构之间的气液界面减小粘性应力。 而在湍流情况下，超疏水表面能够同时减小粘性应力和雷诺应力，使得湍流减阻 效果更加显著。
Currently, most researchers in this field believe that there are mainly two conditions for the formation of super-hydrophobic surfaces. The first condition is the existence of a layer of hydrophobic material on the surface, which can reduce the surface energy. The second condition is the existence of micro and nano structures on the surface. Today there are a lot of methods which could prepare super-hydrophobic surfaces with these two conditions. Chemical vapor deposition, chemical etching, sol-gel method and photolithography, are often used to prepare super-hydrophobic surfaces. Although there are many researches related to the drag reduction on super-hydrophobic surfaces, there is not yet a clear explanation and conclusion about the mechanism. Many researchers have already observed the drag reduction in laminar flow on super-hydrophobic surfaces. However, there are only a few researches which focus on drag reduction in turbulent flow. In addition, most of the super-hydrophobic surfaces using in these experiments only have one-scale micro structures on the surfaces. Super-hydrophobic surfaces, which are more familiar with real lotus leaves, with dual-scale mirco-nano structures are seldom prepared and used in experiments.
本文采用了两种全新的方法制备了具有二级微纳米结构的超疏水表面。测量 了由超疏水表面构建的槽道中的流动压差，将其与普通表面构建的槽道内的流动 压差进行比较，发现在层流情况下，流动阻力减小最多达到了 36.3%。在湍流的情 况下，超疏水表面的减阻比例约为 53.3%，减阻效果比层流更加明显。
在层流下超疏水表面减阻效应的探究性实验中，我们证实层流情况下，超疏 水表面减阻的主要原因是因为微细结构之间的气液界面的存在减小了粘性应力。
关键词：超疏水表面；减阻；二级微纳米复合结构；表面制备
I
Abstract
Abstract
Super-hydrophobic surfaces have been widely applied in modern life and industrial production because of their excellent properties. Super-hydrophobic surfaces have a self-cleaning property. On super-hydrophobic surfaces, liquid could keep as a droplet and easily scroll through the surfaces. In a liquid flow in a channel covered with super-hydrophobic surfaces, there is a significant velocity slip near the wall of the surfaces, which is different from the situation of flows on normal surfaces. In the flow with a micro-level characteristic length, researchers have already observed the slip of the velocity. In recent studies, it was found that the flow drag on super-hydrophobic surfaces is smaller than that on normal surfaces, that is, there is a flow drag reduction on super-hydrophobic surfaces.
目前，学者们认为超疏水表面形成的条件主要有两点，一是表面具有较低的 表面能，二是表面具有微纳结构。目前能够达到这两个条件而制备出超疏水表面 的方法有很多。比如常用的光刻法、化学沉积法，化学刻蚀法以及溶胶凝胶法等 等。对于超疏水表面存在的流动减阻效应，虽然目前已经有一定的研究，但研究 者们对于超疏水表面流动减阻的机理还没有很明确的定论。已经有很多学者在层 流流动中观测到了超疏水表面的流动减阻。然而针对湍流流动中超疏水表面的流 动减阻的研究还相对较少。另外，大部分用于实验的表面都是由只有一级微米结 构构成的表面。针对更接近真实荷叶表面的具有二级微纳米复合结构的表面的流 动阻力特性的研究也相对较少。