Nd:YAG LASER FABRICATION OF SILICON ELECTRODE PLATES FOR A COMBINED-MODE MICRO DIRECT METHANOL FUEL CELL

Abstract

A silicon wafer was microfabricated to produce a new combined-mode flow field for the purpose of distributing methanol fuel throughout the anode side of a micro direct methanol fuel cell (DMFC). Active mode of operation, which generally produces more power, is more suited to higher power requirements compared with the passive mode. Different power outputs using different modes may be required during cell operation by devices that can potentially use the micro DMFC. The new flow field design in the electrode structure of the micro DMFC must manage the methanol fuel transport in either active or passive mode. The flow field area was designed to obtain 50% of the 1 cm 2 active reaction area of the membrane electrode assembly. The proposed design was simulated using COMSOL multi-physics software and microfabricated by incorporating two flow field designs on the anode plate, namely, the grid flow field for the active mode and the porous flow field for the passive mode. The silicon wafer used to produce the electrode plate was a <100> p-type single-sided polished substrate and the MEMS-based microfabrication process to form the required electrode structures was dry etching with laser ablation. The current collector layers used were titanium/copper with a thickness of 1.1 μm and gold with a thickness of 0.18 µm. The completed single-cell micro DMFC obtained a maximum performance of 1.86 mW/cm 2 at a voltage of 138.7 mV.