Cost Effective Fabrication and Characterization of in-Membrane Micro-Fuel Cell

Micro fuel cells (μFCs) have been attracting much attention as a leading candidate for prospective portable power sources and battery replacements [1-3]. Their ability to create an efficient and clean source of energy combined with the ease of portability makes μFCs available to meet the needs of various portable electronic applications in the future [3, 4]. To this purpose, making more efficient devices with cost effective processes and materials is crucial.

Many efforts on fuel cell miniaturization are focused on silicon-based techniques as silicon is the most common substrate in MEMS technology [5, 6]. However, combining silicon devices with polymeric fuel cells at mm or sub-mm scale presents many challenges, none of which have been solved in a completely satisfactory manner [7]. Distinct from previous attempts at fabricating in-plane μFCs by other studies, in this work we present a novel IMμFC (In-Membrane Micro Fuel Cell) design where the micro-flow channels for fuel and oxidant input and the MEA are fabricated using a Nafion membrane as the starting substrate.

The fabrication procedure of IMμFCs has been illustrated in Fig. 1. In preparation for the microfabrication process, 100 μm thick SU-8 photoresist was spin coated, baked and developed to produce a micro stamp. The developed SU-8 on Si wafer was hard baked at 200°C for an hour to enhance the rigidity of the stamps. Fabricated stamps were cut and pressed onto Nafion 1110 membrane at 140°C and 300 psi by a NX2000- Nanoimprinter (Nanonex Corp., NJ, USA). Catalyst loading of conventional Pt/C dispersion on a selected area of microchannels was made by screen printing. Silver wire connections were secured in the designed electrical channels by Kapton tape and carbon black paste. In the sealing step, a laser patterned acrylic sheet was pressed onto the Nafion substrate by the nanoimprinter machine. The fabrication process was completed by mounting the gas inlet tubes on the acrylic sheet side of IMμFCs.

The micro device performance was characterized by I-V polarization curves and impedance spectroscopy under dry and humidified conditions.

Comparing to other studies on μFCs, the presented fabrication approach consists of cost effective processes with a great potential for scale-up production. This new architecture may lead to the deployment of an ultra-low weight, high energy density power source for flat-board-oriented electronic structures.

Refrences:

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2. Taylor, A. D., Lucas, B. D., Guo, L. J., & Thompson, L. T. (2007). Nanoimprinted electrodes for micro-fuel cell applications. Journal of Power Sources, 171(1), 218-223.

3. Kamarudin, S. K., Daud, W. R. W., Ho, S. L., & Hasran, U. A. (2007). Overview on the challenges and developments of micro-direct methanol fuel cells (DMFC).Journal of Power Sources, 163(2), 743-754.

4. Cao, J., Xu, J., Chen, Z., Wang, W., Huang, Q., & Zou, Z. (2013). A silicon‐based micro direct methanol fuel cell stack with a serial flow path design.International Journal of Energy Research, 37(4), 370-376.

5. Shah, K., Shin, W. C., & Besser, R. S. (2004). A PDMS micro proton exchange membrane fuel cell by conventional and non-conventional microfabrication techniques. Sensors and Actuators B: Chemical, 97(2), 157-167.

6. Lu, G. Q., Wang, C. Y., Yen, T. J., & Zhang, X. (2004). Development and characterization of a silicon-based micro direct methanol fuel cell.Electrochimica Acta, 49(5), 821-828.

7. Omosebi, A., & Besser, R. S. (2013). Fabrication and performance evaluation of an in membrane micro-fuel cell. Journal of Power Sources, 242, 672-676.

Figure1. (a) Top-view illustration of μFC design imprinted on Nafion and (b) schematic fabrication steps of the μFC production