MicroFabrication of flow field channels in glassy carbon by a combined laser and reactive ion etching process

Micro structuring of glassy carbon (GC) can be performed by various methods such as sawing, laser ablation, and reactive ion etching (RIE). Our combined laser and reactive ion etching process comprises a laser mask writing step in a sputter-deposited metal layer and a pattern transfer step performed by reactive ion etching. The laser mask writing is achieved by a XeCl laser (308 nm) and a computer controlled setup that allows flexible variation of the pattern. The layout input from plotter files (HPGL) and the writing speed of up to 1 mm/s make this method suitable for rapid prototyping. Subsequent reactive ion etching in oxygen plasma results in channels with trapezoid cross-section, a depth of ∼100 μm, and aspect ratios ∼1.5. A complete flow field with a size of 1 cm2, consisting of 5 meandering channels with a depth of 72 μm and a top width of 59 μm, was prepared for micro fuel cell operation.