Patterned membranes created by 3D printing. Credit: Hickner Group/Penn State
A new type of 3D printing by Penn State will make it possible for the first time to rapidly prototype and test polymer membranes that are patterned for improved performance. Ion exchange membranes are used in many types of energy apps eg fuel cells and certain batteries, as well as in water purification, desalination, removal of heavy metals and food processing. Most ion exchange membranes are thin, flat sheets similar to the plastic wrap in your kitchen drawer. However, recent work has shown that by creating 3D patterns on top of the 2D membrane surface, interesting hydrodynamic properties emerge that can improve ion transport or mitigate fouling, a serious problem in many membrane applications.
Currently, making these patterned membranes, ie profiled membranes, involves a laborious process of etching a silicon mold with the desired pattern, pouring in the polymer and waiting until it hardens which is time-consuming and expensive, and results in a single pattern type. Now Hickner’s team describes a custom 3D photolithographic printing process similar in concept to a current 3D process called stereolithography. They developed a photocurable mixture of ionic polymers and exposed the mixture under a light projector to harden the base layer. They then added more polymer to the base layer and projected a pattern on the new material to selectively harden the surface. The surface pattern increases the conductivity of the membrane by as much as a factor of 2 or 3.
“Membranes act like a resistor in a battery or fuel cell,” says Hickner. “If you can lower the resistance by a factor of two or three, you’ve really got something useful.”
Lead author and a Ph.D. candidate in materials science and engineering, Jiho Seo, added, “A simple parallel resistance model describes the effect of the pattern on lowering the resistance of these new membranes. This insight gives us a design tool to continue to innovate and create new patterns for further improvements along with changing the intrinsic chemistry of the material.” The team will continue to optimize the geometry and chemistry of the membranes they print, as well as learn to print new materials, both for membranes and beyond, never been printed heretofore. http://www.newswise.com/articles/3d-printing-of-patterned-membranes-opens-door-to-rapid-advances-in-membrane-technology
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