Lotus principle and other examples of Superhydrophobic surfaces in nature
There many examples of superhydrophobic biological surfaces in nature. The ability of these surfaces to make water bead off completely and thereby wash off contamination very effectively has been termed the “Lotus effect”, although it is observed not only on the leaves of the Lotus (Nelumbo nucifera L.) but also on many other species, such as Tropaeolum majus L. (Indian Cress/Nasturtium) or Alchemilla vulgaris L. (Lady’s Mantle).
Super-hydrophobicity has also been observed on insects.
The super-hydrophobic biological surfaces have been under thorough study. On such surfaces there is a special morphology. There are surface structures in the micron-scale and also in the nano-scale. The surface structure prevents the water form touching the whole surface. So a water droplet would sit on mostly on the air like the fakir state. In some plants (e.g. Indian Cress) there is a fur on the surface. In particular there are elastic hairs on which the water is resting and so easily removing.
SEM images of the micro- and nano- structure on the surface of the Lotus leaf.
Water droplet on Lotus leaf
8 comments
This area is just fascinating! Imagine how much easier things will become and how much longer things will last once these super hydrophobic surfaces are in the market!
Nice pictures! So we follow nature again e?
Dear Panageotis,
I am working on hydrophoboic calcium carbonate.I am just a student and doing my project work in my university.Tell me where I can find the methodologies of preparing hydrophobic calcium carbonate in nano dimensions.You can refer any book or any journals from where I can find my answers.It will be a great help to me if my prayer is granted.
Thanking you
sumit
If the lotus leaf has a lot of dust with polarity would the water drop lose it´s angle and lay flat on the leaf?
I remember reading The Gecko’s Foot by Peter Forbes and he talked about these sort of hydrophobic/hydrophilic surfaces. It really peaked my interest in this sort of thing. What sort of benefits could you get from a surface like this? From what I’ve read I can only think of cleaning applications and using them on vehicles, airplanes, and watercrafts.
It could be useful almost everywhere. Glasses, building materials, metal protection against corrosion, clothing not need to be washed etc. A big range of products
Lets not forget teapot spouts. At present is the application heat resistant and food safe?
To answer some of your questions: There is much work ongoing in this field. I have, however, never heard of any material being produced that is specifically designed to be “food safe”. But many of the substances/materials used are simply composed of carbon, zinc oxide or teflon. These materials are virtually harmless (has anyone ever died from acute poisoning by eating a piece of burnt toast)? In fact, the materials that I just mentioned are very stable to relatively high temperatures (teflon is about 500*F, and carbon is 4500+*F while ZnO is lower than carbon but still high). Some of the superhydrophobic properties might be reduced at lower temperatures but those temps are still quite high for cooking purposes. Wouldn’t it be great to have superhydro/oleophobic (oil resistant and water resistant) coatings for cookware? Even better than teflon! Usually the problem has been maintaining the nano or microstructured surface when it is exposed to repeated abrasion. It’s difficult.
We are working on superhydrophobic polymers. There have been many developments in this area (it’s a huge area ESPECIALLY if the title of your research project includes the word “nano”). I wouldn’t doubt if there was significant commercial application within the next 10 years if there isn’t already.
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