An artificial gill is a device humans could theoretically use to extract oxygen from water for breathing. Such a device would be invaluable since your air supply would be virtually unlimited.
Unlike rebreathers and tanks which eventually run out of air, scuba divers wearing an artificial gill device could emulate fish and stay underwater potentially forever. Does such an invention exist, and if not, is anyone working on it?
Do Artificial Gills Actually Exist?
Currently, artificial gills are still in realm of science fiction. While a few companies are working on making them a reality, they are still in the very early stages of development.
One of the biggest problems is size. Most animals which filter oxygen from water are cold blooded and have a lower metabolism. Because humans are warm blooded and have a high metabolism, much more oxygen is needed. This means that with our current technology, an artificial gill device which could extract the required oxygen for a single person to breath would be huge – the size of a bus or larger.
This problem is amplified thanks to sea water only containing 7 ppm of oxygen. As a result of this low concentration, 1,000 tonnes of sea water holds only 14 lbs. of O2. Since an average diver needs 1 quart of oxygen per minute, you would need 51 gallons of sea water per minute to pass through the ‘gills’.
An Israeli company, Like-A-Fish, is currently working on making this process more efficient which would allow for smaller devices. In 2006, they begun testing a prototype. Potential applications for a device would be submarines and underwater habitats where size would be less of an issue.
Like-A-Fish’s prototype uses a high-speed centrifuge to lower the pressure of seawater in a sealed chamber. This method lets the air in the water escape back into a gaseous state – much the same way carbon dioxide is released from a soda when you open it. This liberates the O2 which is stored in an airbag for use.
This device has its own drawbacks however, as it relies on battery power which eventually runs out. It also would encounter problems in polluted water and anoxic “dead zones” which are areas in water where available O2 are substantially lower.
Lakshmi Sandhana (2006-01-31). “Inventor develops ‘artificial gills’“. BBC News.
Knafelc, ME. “Oxygen Consumption Rate of Operational Underwater Swimmers.“. United States Navy Experimental Diving Unit Technical Report NEDU-1-89.
Le Page, Michael (2007-01-06). “Breathing in oceans full of air“. New Scientist.