
Spiders and ants inspire metal that won't sink - dnetesn
https://www.rochester.edu/newscenter/superhydrophobic-metal-wont-sink-406272/
======
teh_infallible
As a child, hanging out by the community pool in the summers, I learned the
following trick:

If you can trap and drown a fly, you can then cover the dead fly with salt,
which will suck the water out of the fly, and bring the “resurrected” fly back
to life.

The relevance here: it is surprisingly difficult to drown a fly, because the
weird hairs around their bodies create an air bubble around them, which
protects them. A fly in a bubble of air can survive for at least 20 minutes
underwater. Released, they will float to the surface inside this bubble and
fly away.

Don’t ask how I know.

~~~
maxden
Similar to funnel web spiders. You have to be careful removing 'dead' ones
from a pool as they can survive over 24 hours underwater.

[https://australianmuseum.net.au/learn/animals/spiders/funnel...](https://australianmuseum.net.au/learn/animals/spiders/funnel-
web-spiders-group/)

~~~
airstrike
> australianmuseum.net

Why am I not surprised?

~~~
sudhirj
Yup. Everything in Australia looks scary AF, knows how to play dead and kill
you.

~~~
eloff
Especially those drop bears.

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arkh
Some commenters on reddit are not so hyped by this PR piece.

[https://www.reddit.com/r/science/comments/dssixi/inspired_by...](https://www.reddit.com/r/science/comments/dssixi/inspired_by_diving_bell_spiders_and_rafts_of_fire/f6rprkf/)

~~~
lonelappde
HN has loose posting standards, but /r/science is heavily moderated. They
zealously delete comments witn an inch of speculation, but for some reason
allow University press releases, whose only purpose is to take a science paper
and dress it up in a pile of nonscience for marketing use. I don't understand
why the mods there allow it.

~~~
cjcole
> I don't understand why the mods there allow it.

Precisely because it can result in excellent comments like the current top
comments on the article.

Providing an opportunity for experts to exercise critical analysis is a good
thing and an excellent teaching/learning opportunity.

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pvaldes
Thinking about this method, I think that a much better use for the technique
could be:

1) either engrave the inner surface of metallic parts in airplanes or spatial
stations with a microscopic pattern allowing the recognition ot metal scrapes
stolen or found in the sea after an accident (hours count and you could be
searching in the wrong area). This could accelerate a lot the identification
of the remains and help identifying corpses found next to some metallic part.
Many metallic parts are hollow and as long as the pattern is placed in inner
surface (inside a tube for example) would not create any problem with dirt,
paint or gloss of the final product. That could be a real application.

2) or try to engrave the outer surface to make the airplane surface smoother
without losing too much efficience and properties. I assume that this in hands
of a competent engineer could reduce a little the noise emited by the
airplane.

3) same as point one, but for guns and weapons would be also really useful

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inanutshellus
In short:

> The [metal floats because they use] bursts of lasers to "etch" the surfaces
> of metals with intricate micro- and nanoscale patterns that trap air and
> make the surfaces superhydrophobic, or water repellent.

Neat!

~~~
pvaldes
And will not work in the real life, because they are not paying attention to
biology, just copying it without understanding the ecological processes.

Anything with tiny pores put on the sea will either be covered in life in
weeks, or will need anti-fouling painting to avoid rust and life (distroying
the effect), or this pores will be filled with lime and mud in no time. A ship
hull that is not easily cleanable and can't be polished is creating many new
problems.

I could be wrong but translating this to the real life applications seems
really complicated to implement. Specially when you can just create a sealed
metal box filled with multiple air cameras or a buoy.

~~~
hiccuphippo
They could put it on planes so the material floats and becomes easier to find
in the case of the plane crashing into the sea. Doesn't need to work for long,
only long enough for it to be found.

~~~
PhasmaFelis
The main issue is that this only works on things that are tiny enough that a
micro-layer of surface air can substantially affect their buoyancy. It's a
cool trick, and I'm sure it has uses, but it's not going to do a thing for
planes and ships. It'd be like trying to float a Buick by tying a party
balloon to it.

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Pfhreak
I wonder if this has applications in the food market. Could you make metal
cans/bottles that wouldn't hold their contents? (e.g. a ketchup bottle that
poured out the last drop) Would the uneven surface provide a haven for
bacteria?

~~~
sansnomme
If you want simple hydrophobic properties, just use PTFE coating. It has its
limitations but you don't have to wait for commercialization as the tech is
pretty mature.

~~~
sudhirj
It sounds incredibly toxic, though - Polytetrafluoroethylene.

Would be nicer to just point lasers and the existing cans or glass bottles and
be done with it.

~~~
mikorym
If you call it Teflon, would you be less scared of the name?

~~~
appleflaxen
No. Teflon manufacture has led to long-term contamination of waterways, plus
illness caused be workers exposure ("teflon flu").

So I would prefer nanoengineering to manipulate surface tension.

~~~
akiselev
_> So I would prefer nanoengineering to manipulate surface tension._

Nanotoxicity is a very poorly understood field and any nanomaterials are at
the very least likely to flake away bits that are similar to asbestos.

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ajuc
This changes nothing for ships. Ships float because they already "trap" a huge
"air bubble" inside because of their hull shape. Making the hull walls repel
water might lower the drag but won't change buoyancy.

And after a week these etchings will be covered by sealife and won't work
anyway.

~~~
deaps
The theory here is that if the hull was punctured with a cannon-ball sized
hole, then the one that repels water may still be filled with that air bubble.

I do see your point. This is easier to envision on a smaller scale in
production, however. In theory, if it works for a small vessel, it should also
work for a larger one. Although I don't see large sea-bearing vessels changing
any time soon.

Either way, innovation is cool...and it always starts somewhere.

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moocow01
Without knowing much about ship dynamics it sounds suspicious that you could
make an unsinkable ship based upon this concept. Isn't the above water mass of
the ship held up by the (large) amount of air in the hull? If you punctured
the hull (releasing the air) then wouldn't this material have to support the
entirety of the ship with the minuscule layer of air bubbles across the
surface of the hull? I notice the person's hand pushing the disc down with
relative ease so I'd assume its buoyant but not super-buoyant

~~~
Swizec
It’s not the air holding a ship up, it’s the displaced water. Once the weight
of displaced water is equivalent to the ship’s weight, it floats.

Another way to think about it is specific weight. Ships have fewer kilograms
per cubic meter than water does so they float. When pierced they start filling
up with water which makes their specific weight go up and eventually become
more kilo per cubic meter than water. At that point the ship sinks.

~~~
hahajk
Yes, it’s displaced water... So I’m guessing the trapped air bubbles here
increase the displacement of the water while only adding the weight of the
air? It seems like such a small amount of displacement you’d get from these
tiny air bubbles. Then again, those discs look super thin too.

~~~
Doxin
You'd only need as much air volume as you have volume of things heavier than
water. A boat sinks because air is displaced by water, increasing the density
of the boat. If you make sure the displaceable air runs out _before_ the
density of the boat is higher than water it'll never sink.

In practice this is something that's actually done quite a bit. Fill a lot of
air spaces in a boat with foam and you get to the point where if your boat
fills with water you can simply pull the plug in de bottom of the boat and it
will un-sink itself most of the way. You see this for example on small
sailboats, the only caveat being you can't be on the boat as it's un-sinking
since you'd weigh it down.

That said, seems to me that foam is a lot cheaper and easier than micro-
engineering every surface on the boat.

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Udik
Yes but why not simply a metal honeycomb structure, with air bubbles trapped
permanently _inside_?

Also, an "unsinkable flotation device" can be made out of styrofoam?

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koliber
This looks like a novel and not immediately intuitive way of trapping air in a
narrow space between two plates of metal. Neat.

There are other ways of trapping air between two pieces of metal.

I wonder how this compares against a sandwich of metal-bubble-wrap-metal. Or
with styrofoam, or an injectable foam. It would also float. It would also
withstand multiple punctures. I imagine it is cheaper than etching metal.

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bayesian_horse
If this makes it into warships, we can expect torpedos and anti-ship missiles
to contain something like laundry detergent that stops the bubbles from
forming.

Come to think of it: they better make sure this bubble isn't influenced by
some trivial chemicals, otherwise they don't need explosives to sink a ship...

~~~
dsfyu404ed
If this tech makes it to industry I suspect it will make it to the inside high
performance hydraulics before it makes it to the outside of ships. Those parts
are already manufactured to high tolerances and operate in a chemically
controlled environment. A little etching somewhere in a pump body or in a key
place on an impeller to reduce friction by a percent or two could pay off big
time over the life of the device.

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d--b
Mmmh, you'd need quite a lot of air for your device to be overall lighter than
water...

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blondie9x
Would be awesome to see this done on a model boat to prove out the concept.

~~~
ubercow13
Boats already float

~~~
cbluth
Yeah, but are they made out of ants?

~~~
selimthegrim
Leininger would like a word with you.

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dang
Url changed from [https://phys.org/news/2019-11-spiders-ants-metal-
wont.html](https://phys.org/news/2019-11-spiders-ants-metal-wont.html), which
points to this.

