Chemical Engineering: Breathing Air Out of Water

The 3-ft. tank filled with swimming goldfish looked like any other pet-shop aquarium, but the hamster hopping about inside the tank raised more than a few eyebrows. Sealed in an air-filled chamber, the hamster was staying nicely alive in his underwater environment without the help of lines or pipes leading to the air above the surface.

Keeping the water out of the hamster’s container was an all-but-invisible silicone rubber film. But what was truly remarkable was that the film was acting like a membrane, drawing oxygen out of the water for the hamster to breathe. Just as remarkable, the porous film was also carrying the hamster’s exhaled carbon dioxide into the water.

1/20,000th of an Inch. Silicone rubber is one of the most permeable substances (60 times more so than Teflon film), and General Electric Researcher Walter L. Robb, 36, had long known that it could be made to act like a membrane. Two years ago, Robb hit on a way to stretch the rubber into sheets 1/20,000th of an inch thick, set about trying to devise a way to eliminate the tiny holes that somehow showed up in each square foot of film. His solution was simple: since the probability of two holes being in the same spot on two sheets of film was remote, he laminated two sheets together, making a film 1/10,000th of an inch thick.

Robb now had what amounted to an artificial membrane. Just as the lining of the lungs blocks out liquid blood but lets oxygen in and carbon dioxide out, Robb’s membrane was able to filter through its gossamer skin the tiny dissolved bubbles of oxygen-rich air from water without drawing any of the liquid with it. Robb’s membrane works best in a tank or stream of running water, where bubbles of oxygen are plentiful to draw on. Then the artificial membrane can operate as a gill does when it filters oxygen into a fish’s bloodstream. Indeed, trout breathe best in mountain streams where there is plenty of oxygen in the water.

Air with 35% Oxygen. General Electric says that the silicone membrane is more than a laboratory stunt, and G.E. engineers foresee half a dozen practical applications, not all of which will be water-bound. The membrane’s natural preference for oxygen over most other gases (G.E. scientists, including Robb, do not yet know why) may soon result in a revolutionary unit to supply an enriched mixture of 35% oxygen for military field hospitals as well as in improved breathing systems for spacecraft and submarines. Other possibilities: space suits that cool off astronauts even as they perspire; a substitute for the very expensive heart-lung machine used in open-heart surgery. In this application, the membrane would separate blood and oxygen, perform some of the same functions as a human lung.