A self-pumping and self-breathing micro direct methanol fuel cell with polymer bipolar plates

A passive micro direct methanol fuel cell (DMFC) for reducing volume and parasitic power is designed and fabricated using several integrated technologies. New bipolar plates with tapered channels at the anode and a pillar array at the cathode are first applied to a passive micro-DMFC. The substrate of the bipolar plates made of acrylonitrile butadiene styrene (ABS) is hot embossed with two molds, fabricated by UV-LIGA and micro machining. To make the bipolar plates conductive and hydrophilic, a nickel layer is electroplated on the ABS plates, and three PDDA/PSS bi-layers are self-assembled onto the nickel layer. The bipolar plates are produced using hot embossing, a low cost, highly accurate batch process. A single cell is assembled to verify the self-pumping function, and it can generate a peak power density of 7.4 mW cm^-2 with a 3 M methanol solution. The fuel cell is verified to work in three different orientations. When the fuel cell is placed horizontally, the self-pumping rate is about 0.1-0.15 mL h^-1. And the fuel cell can work through self-pumping for 5 h under this condition.