A silicon-based micro direct methanol fuel cell (muDMFC) for portable applications has been developed and its electrochemical characterization carried out in this study. Anode and cathode flowfields with channel and rib width of 750 mum and channel depth of 400 mum were fabricated on Si wafers using the microelectromechanical system (MEMS) technology. A membrane-electrode assembly (MEA) was specially fabricated to mitigate methanol crossover. This MEA features a modified anode backing structure in which a compact microporous layer is added to create an additional barrier to methanol transport thereby reducing the rate of methanol crossing over the polymer membrane. The cell with the active area of 1.625 cm(2) was assembled by sandwiching the MEA between two micro-fabricated Si wafers. Extensive cell polarization testing demonstrated a maximum power density of 50mW/cm(2) using 2M methanol feed at 60degreesC. When the cell was operated at room temperature, the maximum power density was shown to be about 16 mW/cm(2) with both 2 and 4 M methanol feed. It was further found that the present muDMFC still produced reasonable performance under 8 M methanol solution at room temperature. (C) 2003 Elsevier Ltd. All rights reserved.