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Artificial gills are a device to let a human take in oxygen from surrounding water. This technology does not exist yet or is in early stage of being developed.
Several potential methods exist for the development of artificial gills. Dr Landé has proposed the use of liquid breathing with a membrane oxygenator to solve the problem of carbon dioxide retention, the major limiting factor in liquid breathing.[1][2] It is thought that a system such as this would allow for diving without risk of decompression sickness.[3]
It is generally thought that they would be unwieldy and bulky, because of the massive amount of water that would have to be processed to extract enough oxygen to supply an active diver, as an alternative to a scuba set. However, Like-A-Fish is an ongoing attempt to develop such a system in the real world.
As sea water contains 7 ppm oxygen, 1,000,000 kg (1,000 tonnes) of sea water holds 7 kg (1,000 short tons holds 14 lb) of O2, the equivalent of 5,350 litres (1,410 US gal) of oxygen gas at atmospheric pressure.
An average diver with a fully closed-circuit rebreather needs 1 litre (roughly 1 quart) of oxygen per minute.[4] As a result, at least 192 litres (51 US gal) of sea water per minute would have to be passed through the system, and this system would not work in anoxic water.
Natural gills work because nearly all animals with gills are cold-blooded and so need much less oxygen than a warm-blooded animal of the same size.[5]
Like-A-Fish Technologies is an Israeli business, founded by Alan Bodner in 2001, that is currently testing an artificial gills prototype.[6] Like-A-Fish's technology uses a centrifuge causing lower pressure at the center, where dissolved air comes out of the water.[7]
As with any artificial gill, air from a huge volume of seawater would have to be extracted to provide enough for breathing, requiring large amounts of power for pumping. Therefore, a key issue remaining is battery life. Currently a one kilogram battery would only last for one hour,[6] whereas a regular scuba tank can last longer (depending on depth). Regular scuba gear is also far simpler, and thus safer, as there is less to go wrong.
The biggest possibilities lie in underwater habitats, which have access to electricity, but need constant refilling of air tanks. Other possible uses include systems for submarines, among others.
Like-A-Fish currently holds patents in Europe for its system.[8][9]