April 2006

Vol. 21, No. 4   What's this?

An Artificial Gill for Divers?

from the April, 2006 issue of Undercurrent  

Israeli inventor Alon Bodner has developed an underwater breathing system that literally squeezes oxygen directly from seawater, doing away with the need for tanks.

Called “LikeAFish,” the battery-powered artificial gill extracts small amounts of dissolved air that exist in water to deliver it to the diver. It uses a high-speed centrifuge to lower the pressure of seawater in a small sealed chamber. The dissolved air escapes back into a gaseous state — much as carbon dioxide is liberated from a soft drink when you pop the bottle cap. The air is then transferred into a small impermeable light weight bag, for the diver to breathe.

Bodner’s system must circulate 200 quarts of water/ minute to accommodate the breathing needs of an average diver, he says. A one-kilo battery should be able to supply a diver with one hour of dive time.

Today, his system exists as a laboratory model with approved European patents and US patents pending. He eventually plans to reduce the size of the apparatus to a small, lightweight vest for divers.

Some people like Mike Rowley, a British Sub Aqua Club Instructor, aren’t so sure it will serve divers. Bodner makes the assumption that a closed-circuit rebreather diver will use a quart of oxygen per minute. However, with heavy swimming against a strong current this can require at least 3.5 quarts/ minute. Says Bodner, the device will need “some form of reserve capacity to enable it to cope with lengthy periods of high oxygen metabolism.” And that would mean a much larger device, perhaps too large to make it practical for divers.

Craig Billingham, a technical diving instructor, says to get the time one gets from a rebreather or twin tanks, you will need a lot of batteries. “Also batteries and seawater don’t mix. It isn’t a case of if it leaks but when.”

Bodner says that it would be undesirable to use the system if the water lacks oxygen or is polluted. A small compressed air tank built into the system could act as a reserve in case of battery failure. He says a fully functional prototype is about two years away.

By Lakshmi Sandhana, BBC News, January 31, 2006