July/August 2011

Nafion increases water flow, filtering

Researchers at Virginia Tech in Blacksburg, Va., recently found a way to improve electricity generating fuel cells, potentially making them more efficient, powerful, and less expensive. Specifically, they discovered a way to speed up the flow and filtering of water or ions, which are necessary for fuel cells to operate, according to The National Science Foundation (NSF). The researchers stretched Nafion, a polymer electrolyte membrane, or PEM, commonly used in fuel cells and increased the speed at which it selectively filters substances from ions and water.

The resulting process could be important to a number of energy and environment-related applications such as any of several industrial processes that involve filtering, including improving batteries in cars, water desalination, and even the production of artificial muscles for robots.

In order to improve PEMs, Louis Madsen and Robert Moore studied exactly how water moves through Nafion at the molecular level and measured how changes in the structure of the material affected water flow. They found stretching it caused channels in the PEM material to align in the direction of the stretch, allowing water to flow through faster.

"Stretching drastically influences the degree of alignment," said Madsen. "So the molecules move faster along the direction of the stretch, and in a very predictable way. These materials actually share some properties with liquid crystals-molecules that line up with each other and are used in every LCD television, projector, and screen."

"This is a very clever approach, which demonstrates the advantages of interdisciplinary materials research and which may offer important benefits to both energy technologies and sustainability of our natural resources," said Andy Lovinger, polymers program director in the NSF's Division of Materials Research, which funded the study.

Nafion was discovered in the 1960s and is made up of molecules that combine the non-stick and tough nature of Teflon with the conductive properties of an acid. It is one of many PEMs used to filter water and ions that the researchers say could benefit from the stretching process.

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