An air-breathing micro direct methanol fuel cell (mu DMFC) with a water collecting and recycling cathode structure is presented in this paper. The mechanism of water generation in cathode and water collection from the cathode is studied. The capillary channels with hydrophilic surface are designed along the ribs of the air-breathing cathode window to collect excessive water. The collected water is then released via an exhaust pipe. Microfabrication techniques, including double-side lithography and KOH etching, are used to fabricate the anode and cathode plates of the mu DMFC on the same silicon wafer simultaneously. The silicon plate surface is treated by low temperature oxygen plasma to improve the hydrophilicity. The mu DMFC with the water collecting and recycling structure and the regular one without, both with an active area of 7.8 x 7.8 mm(2), are assembled and characterized. Experimental results show that the maximum power density and current density of the both mu DMFCs are more than 10 mW cm(-2) and nearly 100 mA cm(-2) at room temperature, respectively. After both mu DMFCs operate at 0.15 V (about 60 mA cm(-2) at room temperature) for 1 h, the outputs of the prototype with water collecting and recycling structure decrease to about 9.7 mW cm(-2) and 95 mA cm(-2) only, while that of regular one decrease to 9 mW cm(-2) and 75 mA cm(-2). The water is collected by the exhaust pipe in evidence. As such, it would be possible to recycle the water from cathode to anode. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.