朴茨茅斯大学 垃圾:荷叶的成份是？

你好,我也没有找到,有一篇英文文献,但是只有摘要.你看看这些把!
Superhydrophobic surfaces have important technical applications ranging from self-cleaning window glasses, paints, and fabrics to low-friction surfaces. The archetype superhydrophobic surface is that of the lotus leaf. When rain falls on lotus leaves, water beads up with a contact angle in the superhydrophobic range of about 160°. The water drops promptly roll off the leaves collecting dirt along the way. This lotus effect has, in recent years, stimulated much research effort worldwide in the fabrication of surfaces with superhydrophobicity. But, is the lotus surface truly superhydrophobic? This work shows that the lotus leaves can be either hydrophobic or hydrophilic, depending on how the water gets on to their surfaces. This finding has significant ramifications on how to make and use superhydrophobic surfaces. ©2005 American Institute of Physics

Today, thousands of buildings boast self-cleaning paint and self-cleaning roofs; self-cleaning textiles, glass windows and sprays have already sprung onto the market. German botanist Wilhelm Barthlott has even owned a patent, copyright and trademark on this self-cleaning phenomenon since 1997. But despite the development of these practical applications, scientists still have a lot to learn about the specific mechanisms behind self-cleaning – or the so-called “Lotus Effect.”

The lotus – a type of water lily native to Asia – has had its praises sung for thousands of years. In religious symbolism, Buddha often sits on a lotus leaf. Hindus view the lotus blossom as a symbol of divine beauty, associating the unfolding of the petals with the expansion of the soul. More recently, botany and nanotechnology have united to explore not only the beauty and cleanliness of the leaf, but also its lack of contamination and bacteria, despite its dwelling in dirty ponds.

These images from a scanning electron microscope compare (a) an untreated lotus leaf, with micro- and nano-scale structures, with (b) an annealed lotus leaf, where the nano-hairs have been melted away. The annealed leaf restricts the rolling, self-cleaning ability of raindrops. Image source: Cheng, Y. T. et al.
In recent years, scientists have developed theoretical models of the underlying mechanisms of the lotus leaf’s self-cleaning properties. Basically, the lotus leaf has two levels of structure affecting this behavior – micro-scale bumps and nano-scale hair-like structures – coupled with the leaf’s waxy chemical composition. However, research has not included a systematic, experimental investigation isolating structural and compositional effects, until now.

“What are the mechanisms giving rise to the lotus effect?” asked scientists from Michigan (Y. T. Cheng et al) who published a paper in Nanotechnology on February 10. “We are able to separate the effects of nanometer features from micrometer roughness… [which] may help design self-cleaning surfaces and improve our understanding of wetting mechanisms.”

The self-cleaning property of the lotus leaf – and applications derived from nature’s model – requires the surface to have roughness on two scales. When a raindrop falls on a lotus leaf, it forms a high contact angle (greater than 90 degrees), which means that it beads up rather than spreads out, as a liquid with a low contact angle (less than 90 degrees) would. A lotus leaf can have a contact angle close to 170 degrees, making it extremely hydrophobic. (For reference, human skin is slightly hydrophobic with about a 90-degree contact angle.) In fact, as little as 2-3% of the raindrop actually contacts the surface of a lotus leaf due to the waxy composition of the leaf, and to the air trapped between the raindrop and the leaf’s micro- and nano-structures.
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(Ads by Google)With such a small amount of contact between water and leaf, the raindrop rolls – rather than slides – down the leaf with little friction. The drop collects dirt and bacteria on its way, and in effect cleans itself.
The Michigan team compared how the self-cleaning property would perform on a lotus leaf with both micro- and nano-structures or with only micro-structures to a lotus leaf. They also compared water drops on a piece of waxed cast smooth on glass. The scientists annealed (a process of heating and slow cooling) a sample of the leaves to melt the nano-scale hair structure while retaining the wax composition without chemical change. The team measured a significantly lower contact angle for the leaf with only micro-structures (126 degrees) and even lower for the smooth wax (74 degrees), compared with the contact angle of the two-structured leaf (142 degrees).
“The presence of the nano-scale hair-like structure is responsible for the additional increase of 16 degrees in contact angle,” the scientists report. “The two-level roughness, in particular, the nano-scale hairs, amplifies the apparent contact angle and is responsible for the rolling behavior of the drops.”
This study marks the first time that the effect of the nano-hairs has been isolated from the microstructure and chemical composition of the leaf. The results verify the importance of the nano-structure on the lotus leaf’s self-cleaning ability – an essential understanding for inventors designing self-cleaning products in the future.
Reference: Cheng, Y T, Rodak, D E, Wong, C A and Hayden C A. “Effects of micro- and nano-structures on the self-cleaning behaviour of lotus leaves.” Nanotechnology 17 (2006) 1359-1362.

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上面答案都不对！
为什么荷叶的防水性能能那么好？为什么？
答：荷叶表面的蜡质层是憎水化合物，所以能够防水。

水在上面成珠而又不渗透？？？？
答：水珠不能浸润荷叶表面的很厚的一层蜡质层，产生表面张力现象，形成类似于球的形状，要是浸润的话就平铺上去一层水膜了。

问题补充：呵呵！！最好能给出该成份的组成！！谢谢各位啦！！
答：荷叶蜡质层的主要成分是高碳脂肪酸和高碳一元脂肪醇，主要是10－20个偶数碳原子。
具体有：
癸醇
月桂醇
月桂酸(lauric acid，C12)
棕榈酸(palmitic acid，C16)。
十六醇
十八醇
硬脂酸
二十醇
二十烷酸
..........

荷叶的表面是一有规则的微结构表面,能够防止液滴浸湿表面,该微结构使液滴和涂层表面之间藏有空气,具有自洁作用,即超级防护性。

荷叶的表面是一有规则的微结构表面,能够防止液滴浸湿表面,该微结构使液滴和涂层表面之间藏有空气,具有自洁作用,即超级防护性。

荷叶的表面是一有规则的微结构表面,能够防止液滴浸湿表面,该微结构使液滴和涂层表面之间藏有空气,具有自洁作用,即超级防护性。...荷叶是常用的减肥轻身之品,可升清降浊,生发元气,裨助脾胃,与泽泻同用,在祛脂减肥的同时减少肥胖者肝内脂肪

荷叶的表面是一有规则的微结构表面,能够防止液滴浸湿表面,该微结构使液滴和涂层表面之间藏有空气,具有自洁作用,即超级防护性。

荷叶的表面是一有规则的微结构表面,能够防止液滴浸湿表面,该微结构使液滴和涂层表面之间藏有空气,具有自洁作用,即超级防护性。