Artificial gills (human)
Encyclopedia
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.
with a membrane oxygenator
to solve the problem of carbon dioxide
retention, the major limiting factor in liquid breathing. It is thought that a system such as this would allow for diving without risk of decompression sickness
.
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 5350 litres (1,413.3 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. As a result, at least 192 litres (50.7 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 gill
s 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.
i business, founded by Alan Bodner in 2001, that is currently testing an artificial gills prototype. Like-A-Fish's technology uses a centrifuge
causing lower pressure at the center, where dissolved air comes out of the water.
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, 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.
Methods
Several potential methods exist for the development of artificial gills. Dr Landé has proposed the use of liquid breathingLiquid breathing
Liquid breathing is a form of respiration in which a normally air-breathing organism breathes an oxygen-rich liquid , rather than breathing air....
with a membrane oxygenator
Membrane oxygenator
A membrane oxygenator is a device used to add oxygen to, and remove carbon dioxide from the blood. It can be used in two principal modes: to imitate the function of the lungs in cardiopulmonary bypass , and to oxygenate blood in longer term life support, termed extracorporeal membrane oxygenation,...
to solve the problem of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
retention, the major limiting factor in liquid breathing. It is thought that a system such as this would allow for diving without risk of decompression sickness
Decompression sickness
Decompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
.
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
Scuba set
A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving. It is much used for sport diving and some sorts of work diving....
. 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 5350 litres (1,413.3 US gal) of oxygen gas at atmospheric pressure.
An average diver with a fully closed-circuit rebreather
Rebreather
A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...
needs 1 litre (roughly 1 quart) of oxygen per minute. As a result, at least 192 litres (50.7 US gal) of sea water per minute would have to be passed through the system, and this system would not work in anoxic
Hypoxia (environmental)
Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...
water.
Natural gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s work because nearly all animals with gills are cold-blooded
Poikilotherm
A poikilotherm is an organism whose internal temperature varies considerably. It is the opposite of a homeotherm, an organism which maintains thermal homeostasis. Usually the variation is a consequence of variation in the ambient environmental temperature...
and so need much less oxygen than a warm-blooded
Warm-blooded
The term warm-blooded is a colloquial term to describe animal species which have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes...
animal of the same size.
Like-A-Fish
Like-A-Fish Technologies is an IsraelIsrael
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
i business, founded by Alan Bodner in 2001, that is currently testing an artificial gills prototype. Like-A-Fish's technology uses a centrifuge
Centrifuge
A centrifuge is a piece of equipment, generally driven by an electric motor , that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis...
causing lower pressure at the center, where dissolved air comes out of the water.
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
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
life. Currently a one kilogram battery would only last for one hour, whereas a regular scuba
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....
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.
External links
- New Scientist article - history of attempts to develop artificial gills and the principles and problems involved (subscription required)
- BBC Article A BBC article about the Like-A-Fish system
- www.likeafish.biz Official website
- 'Like A Fish' Underwater Breathing System: Artificial Gills for U.S. Navy SEALs?
- Specific publication reference dates from an unusual source