CO2 gas bubbles have a great effect on the &mgr;DMFC (Micro Direct Methanol Fuel Cell) as the anode resultants.
Visualization technique is one of the most important tools to study the formation, movement, and removal of CO2 gas
bubbles. This paper presents an air-breathing micro direct methanol fuel cell made of PMMA for the visualization
research. Four types of flow fields are fabricated in the anode plates. Different from the traditional &mgr;DMFCs, the
stainless steel mesh is adopted as the current collector. The observation and study of CO2 bubbles behavior show that the
quantities and bulks of CO2 gas bubbles increased as the current densities became higher. In addition, anode methanol
solution flow rates and cell orientations also have complicated influence on the &mgr;DMFC performance.
We designed and fabricated a new portable passive DMFC stack with its volume significantly reduced. Its high
efficiency and load regulation performance were also demonstrated through experiments, and its stability seemed to be
very good. We achieved a maximum power density of 3.9mW/cm2 with a 2M methanol concentration under ambient
conditions. This performance is better than that of a conventional DMFC. The volume of the 10-cell series connection
DMFC stack is only 42mm x 42mm x 40mm. Due to its stable performance and easy fabrication, this structure is believed
to be applicable for portable small-scale DMFC stack.