Artificial gills - how?

CEngelbrecht said:

Found a website some time ago, that claimed to have figured out how to make a gismo that allowed you to breathe oxygen from the surrounding water, and they were seeking crowd funding to get it on the market. Sounded very exciting, however, a quick readthrough of the claimed principle showed it as a massive hoax, trying to steal mo money from the gulliple of the world.



But... just out of curiosity... could it be made to work? Like, you put on some kind of stormtrooper helmet, which then diffuses oxygen in and diffuses excess carbon dioxide out into the surrounding water, allowing you to breathe inside an air bubble constantly being automatically kept at set levels of O2 and CO2 (and N2?), and then you could be under water as long as you like, with limited bulky equipment and no gas limit from a SCUBA tank.

Would there still be issues of decompression sickness and nitrogen narcosis, is what I can't figure out right now. And how deep would you be able to go before physics would still kill you? Tens of meters? Hundreds? Thousands? Provided that the diffusion issue could even be solved.


(A game I played recently, where your character wore a helmet and could stay under water indefinitely.)

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REVAN said:

What you are hoping for is, I think, the wrong approach. There is generally not enough O2 dissolved in the water to support the high metabolism of a human with any reasonable sized system. The diver would be hooked to a gill machine the size of a refrigerator. However, there is another approach I have considered that may have merit.

Rebreathers can provide several hours of O2 from a very small oxygen tank. The big Achilles' heel to the rebreather is the CO2 scrubber. The absorbent is problematic and expensive. It can go bad. It can become saturated. It can channel and fail to remove the CO2. If it gets wet, it will poison your breathing air. Etc....

However, water likes to absorb CO2 to form a weak carbonic acid. A gas permeable material could be used to make a reverse gill; a gill that exchanges CO2 into the water, but the system would still get it's O2 from a small bottle like a rebreather. My gut feeling is that this could be done with a reasonable sized gill that could be worn by a diver, as opposed to something the size of a major household appliance. If it could be made to work, it would revolutionize rebreather technology, making it almost as easy and cost effective to use as OC nitrox.

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pegcjs said:

Interesting idea. One could argue that the biggest problem and risk of RB is not the scrubber but sensor failure. I hate having to spend so much on new ones.
How about using the water as the O2 source by electrolysis as well as scrubber though? . Then the unit replaces O2 cylinder with batteries and the water is doing both.

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