Rectangular node electrodes were developed with micro-fabrication techniques in order to produce an electrolytic micro-bubbler which, while subjected to a convective flow, can generate bubbles of nearly uniform size with mean diameters of 50 mu m or less. The devices were fabricated and placed in both a quiescent tap water chamber and a water channel operating at laminar flow rates. The effect of applied voltage and flow conditions on the bubbles generated was tested on single electrode pairs. Videos of the bubbles generated by the devices were taken from which the bubble sizes and generation rates were recorded. It was found that higher applied voltages coincided with smaller average bubble size, a narrower distribution of bubble sizes, higher bubble fluxes, and a higher current efficiency. The imposition of a hydrodynamic flow was shown to reduce average bubble size, narrow the range of bubble sizes, and reduce current efficiency. Smaller electrode nodes were seen to reduce the number of active nucleation sites and thus produced a narrower bubble size distribution. In the best case, the bubble distribution was nearly mono-disperse with a small average bubble diameter (ca. 40 mu m) with repeatable mean bubble diameters and bubble fluxes. Intermediate values of the ratio of electrode node width and cathode/anode spacing provided the largest average bubble diameters. (c) 2005 Elsevier Ltd. All rights reserved.