The fabrication of high-aspect-ratio micro-flow channels on metallic bipolar plates using die-sinking micro-electrical discharge machining

This study explores the feasibility of using a relatively rapid technique, die-sinking micro-electrical discharge machining, to fabricate miniature metallic bipolar plates. The flow field is a three-pass serpentine structure, of which both the rib and channel widths are 500 μm and the channel depth is 600 μm (aspect ratio = 1.2) in a reaction area of 20 mm × 20 mm. The material-removal rate of the proposed method can reach up to 7.2 mm3 min−1. However, a high material-removal rate also increases the surface roughness of flow channels. In single-cell tests, the peak power densities are 674 mW cm−2 and 647 mW cm−2 for flow channels with a surface roughness of 0.715 μm Ra and 0.994 μm Ra, respectively. Though the increase in surface roughness lowers cell performance, the effect is not statistically significant.

► High-aspect-ratio micro flow channels on SUS316L bipolar plates.
► Die-sinking micro-EDM at high material-removal rate (7.2 mm3 min−1).
► A high material-removal rate increases the surface roughness of flow channels.
► The effect of channel roughness on cell performance is not significant.
► Cell size is minimized and relatively high power density is provided.