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.
There’s a simpler way to resurrect a seemingly dead fly, sometimes used as a magic trick. Put a live fly in the freezer. When it is cold enough it starts to hibernate and will appear to be dead. Just holding it in the palm of your hand gives it enough heat to warm up and come to life again.
Great contribution. Key criticism from my standpoint:
...The buoyancy provided by superhydrophobicity scales
with surface area, while the mass of a ship scales with
volume, so this can only ever work for roughly coin-sized
objects. ...
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.
Yup. Even disregarding the problems mentioned in the linked post, it isn't going to work well for real-world applications.
Fresh or saltwater, any vessel is subject to corrosion and the accumulation of grime (or worse, like barnacles). In the demo video, note that the demonstrator is using gloves and isn't even touching the "coin" directly, but using tweezers.
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
> 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.
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.
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.
> Anything with tiny pores put on the sea will either be covered in life in weeks
My question with this, is that if an air bubble is formed against the surface of the material and thus the water is not touching the surface.. how does the life inside the water attach itself to the surface which it does not touch?
terry pratchett's discworld series had hydrophobic wizards raised on dehydrated water that were so hydrophobic that the air around them could displace large amounts of water allowing for water travel.
Cool. It would be even cooler if they could make an "aerophobic" material so it floats in the air. Put some of it on the bottom side of a skateboard and you have a hoverboard (hopefully!).
It's fun to daydream about, but even if you could somehow warp surface tension to hold bubbles of vacuum against a surface, displacing air gives you less than 1/750th as much lift as displacing water.
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?
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.
I wonder if PTFE coatings would serve as an effective bottom coat, I've never heard of it being used on sailboats but it seems like an obvious avenue to explore.
The tech. described in TFA sounds like something that would make for an awful bottom coat, since such surfaces tend to promote growth by providing something attachable.
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.
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.
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
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.
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.
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.
Readit News
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.
https://australianmuseum.net.au/learn/animals/spiders/funnel...
Why am I not surprised?
Can’t say I condone this, it seems rather cruel.
https://www.reddit.com/r/science/comments/dssixi/inspired_by...
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.
Fresh or saltwater, any vessel is subject to corrosion and the accumulation of grime (or worse, like barnacles). In the demo video, note that the demonstrator is using gloves and isn't even touching the "coin" directly, but using tweezers.
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
> 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!
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.
My question with this, is that if an air bubble is formed against the surface of the material and thus the water is not touching the surface.. how does the life inside the water attach itself to the surface which it does not touch?
The tech. described in TFA sounds like something that would make for an awful bottom coat, since such surfaces tend to promote growth by providing something attachable.
Would be nicer to just point lasers and the existing cans or glass bottles and be done with it.
And after a week these etchings will be covered by sealife and won't work anyway.
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.
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.
But why so complicated? A 10cm metal hull seems much safer than a 5mm opening with hydrophobic coating.
Also with a chamber system ship's can be made pretty robust and almost unsinkable.
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.