Remain dry underwater

Discussion in 'Chemistry' started by timojin, Aug 20, 2015.

  1. timojin Valued Senior Member

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    Bugs underwater remain dry due to surface texture
     
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  3. exchemist Valued Senior Member

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    What is your point?
     
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  5. timojin Valued Senior Member

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    I suppose a challenge to Chemist like you, as what mechanism is used or what kind of surface is necessary to remain to be dry
     
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  7. spidergoat Valued Senior Member

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    They have tiny ridges which limit surface contact area.
     
  8. exchemist Valued Senior Member

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    I don't know, actually. But I imagine they may exploit the effect of a hydrophobic surface coating on the angle of contact, which is part of the phenomenon of surface tension. The angle of contact of a hydrophobic surface is large, due to the repulsion of water molecules from the interface. With a surface with ridges (as Spidergoat mentions) or with hairs, they may be able to engineer a situation where there is almost no wetting of the surface at all.

    I admit this is speculation on my part, as I am not an entomologist.
     
  9. spidergoat Valued Senior Member

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    It's a fairly well known phenomenon, seen in lotus plants too, that can be reproduced in metal using standard machine tools.
     
  10. exchemist Valued Senior Member

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    Ah, you speak in riddles, Glasshopper.

    Can you give an example in metal? I'm really intrigued.
     
  11. Secular Sanity Registered Senior Member

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    Last edited: Aug 20, 2015
  12. spidergoat Valued Senior Member

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  13. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I did that about 7 weeks ago, in my car passing thru the Holland Tunnel.
     
  14. timojin Valued Senior Member

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    [QUOTE="exchemist, post: 3322421, member: 268413"
    I admit this is speculation on my part, as I am not an entomologist.[/QUOTE]
    You are rusting away, Ex. here I found something for you
    Ot is the capillary were gas gets trapped and it does not permit the water to reach the surface of the capillary
     
  15. exchemist Valued Senior Member

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    You are rusting away, Ex. here I found something for you
    Ot is the capillary were gas gets trapped and it does not permit the water to reach the surface of the capillary[/QUOTE]

    Sorry, "Ot is the capillary…"???. Can you try that again in better English?

    I'm not sure what you mean by "capillary" here, or by "gas getting trapped". Gas won't just stay "trapped", in the absence of a film of something that traps it. Under water, such a trapping film is formed by….the surface tension of the water.

    Isn't it?
     
  16. exchemist Valued Senior Member

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  17. Secular Sanity Registered Senior Member

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    Hmm…am I hellbanned or on your ignore list? Spidergoat provided a link with just the coating, not the metal itself. I provided you with a link that contained this video, which shows the technique they use with lasers to render the material hydrophobic.
     
  18. exchemist Valued Senior Member

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    Not yet on my ignore list, no. You've only made 14 posts, so give me a chance!

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    Actually I must confess that, since you did not give any text describing what your links were about, I did not read them. (A lot of our more stupid posters regularly give links without any accompanying description - more often than not to YouTube videos full of shite - so I'm afraid I have rather got into the habit of ignoring unexplained links, unless I know and trust the person doing it.)

    I've now looked at your links and see there is a nanometre-scale surface finish - of some unspecified kind- applied to the metal. Interesting. However I still did not see any explanation of what the finish is and why it results in repulsion of water molecules. This is the bit that interests me, as a chemist. Can you explain it?
     
  19. Secular Sanity Registered Senior Member

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    Well, it’s not my first rodeo. Let’s just put it that way. I’m a bad little nonconformist.

    Just like spidergoat said, it mimics the lotus leaf.

    “And like the lotus leaf, because the laser-patterned metal is so water-repellent, it has self-cleaning properties.

    He mentioned toilets, being able to keep them clean without using any water. Me, I’m thinking you guys have a hard enough time hitting the target as it is. We’d have piss bouncing everywhere.

    Here you go.
     
  20. sideshowbob Sorry, wrong number. Valued Senior Member

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    I would think that keeping water out of various openings is more important than keeping the surfaces dry.
     
  21. exchemist Valued Senior Member

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    Not for tiny insects. For these, the surface tension will be easily enough to stop water getting into openings.
     
  22. exchemist Valued Senior Member

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    OK, so regarding my question, about the mechanism by which the surface treatment causes the surface to be so strongly hydrophobic, no dice, eh?
     
  23. timojin Valued Senior Member

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