A new type of 3D printing will make it possible for the first time to rapidly prototype and test polymer membranes that are patterned for improved performance, according to Penn State researchers.
Ion exchange membranes are used in many types of energy applications, such as fuel cells and certain batteries, as well as in water purification, desalination, removal of heavy metals and food processing. Most of these 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, also called profiled membranes, involves a laborious process of etching a silicon mold with the desired pattern, pouring in the polymer and waiting until it hardens. The process is both time-consuming and expensive, and results in a single pattern type.
"We thought if we could use 3D printing to fabricate our custom-synthesized ion exchange membranes, we could make any sort of pattern and we could make it quickly," says Michael Hickner, associate professor of materials science and engineering, Penn State.
In a paper published online today in the American Chemical Society's journal ACS Applied Materials and Interfaces, Hickner's team describes the development of a custom 3D photolithographic printing process similar in concept to a current 3D process called stereolithography. The team 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 two or three.
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