Lotus Leaves, Rose Petals and Nano-Soccer Balls: What the Fakir could these have in common? (No, I’m not using a bad word, check out the title of the respectable PNAS paper below 🙂
The Lotus Effect: A symbol of purity – the leaves of a lotus are always clean and dry. Water simply rolls off the surface, carrying dirt with it. This self-cleaning property is due to the superhydrophobic surface of the lotus leaf. Studded with micropapillae (image), water beads lie on the top like a fakir on a bed of nails. While ordinary waxy surfaces may have contact angles of >90° with the drop, fakir drops show extreme angles of 170°, minimizing contact to only 0.6% of their surface! In the virtual absence of adhesive forces, the drops skitter off, cleaning the leaf as they roll (The Lotus-Effect: CGI simulation).
The Petal Effect: While a water droplet on a rose petal is spherical, it does not roll off, even if the flower is held upside down. This is because the petal’s nanostructure allows the water to wet the space between the surface grooves, increasing adhesive forces (Wenzel model pix; http://goo.gl/GT7KF). Contrast this to the lotus leaf, where the drop sits on the ‘bed of nails’ with trapped air in between (Cassie-Baxter model pix; http://goo.gl/35Cz6).
Why do we care?: There is a wealth of nanotechnology drawing upon Nature’s brilliance. Watch this wonderful video: http://goo.gl/dXMQ2
More recently, scientists in the Netherlands figured out a way of packaging nanoparticles, that could be used to deliver drugs for example, into soccer ball-like clusters of very high density, by slowly evaporating solutions from a superhydrophobic effect. They show that fakir drops remain in the Cassie-Baxter mode without collapsing into the Wenzel mode. (Aren’t you glad you now know what that means!).
REF: Building microscopic soccer balls with evaporating colloidal fakir drops:
Good morning, Shinae Choi Robinson 🙂
I wanted to tell you that I tried your recipe for pickling ginger and it was great (turned pink too!). Your noodle salad with mixed greens was a hit with the family (will share pix when I get them off the camera).
This is awesome info. Ta!
That reminds me of this really cool (but also really esoteric) use of superhydrophobic surfaces: Superhydrophobic droplet logic
Noah Maze , that is brilliant! Thank you.
What a cool way to design logic gates.
Thank you Rajini Rao for the little Nature lesson 🙂 I always learn something new from your posts.
My thinking is more simplistic than yours, but it would be cool if scientists could somehow make outdoor paint act like fakir drops. Just imagine that you don’t need to wash your car ever again hehe
Rose Le , indeed there is a paint product called Lotusan as well as other nifty things like extreme water repellent coating on car windshield. I’d like a lotus coating on my car too (now you’ve reminded me how dirty it is, lol).
Did I spell it wrong Chad Haney ? It is a compound word of super + hydrophobic. That’s the technical name for it.
It’s typed wrong twice. You are supposed to spell check me. Not the other way around.
superhydrophic vs. superhydrophobic
LOL, so it is! Edited, thanks. Spell check credits to Chad Haney for future reimbursement 😉
I think we are even, Rajini Rao I had some embarrassing typos on the SS Event.
In pic – Rose or Lotus leaf.. Dear Scientist.. ?
Lotus leaf, Avinash Dixit 🙂
Interesting Magnified picture !… All smooth looking things are not Actually that much smooth in the Nature.. We must take care while being too close to them !!! ;
Like water off a duck’s back, Feisal Kamil 🙂
Avinash Dixit , that’s a good point. The lotus leaf owes it’s super slippery surface not to smoothness but a rough surface. Who could have guessed?
Some desert insects use water repelling on their shells to collect and channel water to their mouths in the mornings. The military have been studying these to extract water from the air.
Akira Bergman , that’s right. I heard it in the ABC news story/video that I linked to in the post: http://goo.gl/dXMQ2
An interesting aspect of this, Rajini Rao , is the paradox of the water repelling being used for collecting it.
Exactly! Just like the paradox of smooth lotus leaves owing to their rough microsurface, Akira Bergman 🙂
any fabric like this?
Xiao-Pei Guan I know Clemson University was working on some nano coating techniques for polymer fibers using Ag colloids as templates to create the bed of nails as recently as 4 years ago. You’d have to check the literature but yes there are many groups working on lotus effect fabrics.
That’s interesting, Mark Bruce . If you find a link sometime, I’d like to know more. The material is optically sensitive?
We exploit this effect quite a bit – the challenge is to make these structures durable in the environment in which you’d like to use them.
The superhydrophobic effect in coating materials? Very interesting!
Getting ready to leave for work or do you have the day off, Feisal Kamil ? School/Univ/NASA shut down tomorrow. I love the Govt. Code Red: non essential employees stay home. This way I can tweak my husband: you mean you’re not essential? :O
OK, well I’m off to get some sleep before Sandy arrives! Catch you later, hopefully.