The influence of the channel radius on the mass transfer in rectangular meandering microchannels (width 200-400 mu m and height of 150 gm) has been investigated for gas-liquid flow. Laser induced velocimetry measurements have been compared with theoretical results. The symmetrical velocity profile, known from the straight channel, was found to change to an asymmetrical one for the meandering channel configuration. The changes in the secondary velocity profile lead to an enhanced radial mass transfer inside the liquid slug, resulting in a reduced mixing length. In the investigated experimental range (superficial gas velocity 0.08 m/s and superficial liquid velocity 0.01-0.07 m/s) the mixing time was reduced eightfold solely due to changes in channel geometry. An experimental study on the liquid slug lengths, the pressure drop and their relation to the mass transfer have also been performed. Experimental results were validated by a simulation done in Comsol Multiphysics (R). To obtain information for higher velocity rates, simulations were performed up to 0.64 m/s. These velocity variations in the simulation indicate the occurrence of a different flow pattern for high velocities, leading to further mass transfer intensification. (c) 2008 Elsevier Ltd. All rights reserved.