Optimization of Nafion polymer electrolyte membrane design and microfabrication

Marland, Jamie R.K. and Moore, Fiona and Dunare, Camelia and Tsiamis, Andreas and Gonzalez-Fernandez, Eva and Blair, Ewen O. and Smith, Stewart and Terry, Jonathan G. and Murray, Alan F. and Walton, Anthony J. (2020) Optimization of Nafion polymer electrolyte membrane design and microfabrication. IEEE Transactions on Semiconductor Manufacturing, 33 (2). pp. 196-201. ISSN 0894-6507 (https://doi.org/10.1109/TSM.2020.2983875)

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Nafion is a solid electrolyte polymer that can be used as a sensor membrane in microfabricated electrochemical oxygen sensors. It allows ions to be transported between the sensor electrodes and removes the need for a liquid electrolyte. Here we used a series of small square Nafion test structures, fabricated on a variety of materials using standard thin-film patterning techniques, to optimize the design and processing of Nafion membranes. Measurements showed that the choice of photoresist developer is critical. Use of diluted MF-26A developer provided the most effective and manufacturable process. The underlying material also had an influence on robustness, with silicon dioxide and platinum giving the longest membrane lifetime under simulated conditions of use. Membrane size had no clear effect on lifetime, and under optimal processing conditions there were minimal failures even under continuous mechanical agitation for up to six weeks. We also developed test electrodes covered by Nafion, and showed that they were effective at supporting electrochemical oxygen detection.