A novel multi-scale micromixer with arborescent structure for high throughput gas-liquid mixing was evaluated by absorbing pure CO2 into alkaline solutions, and the volumetric mass transfer coefficient, interface area, liquid side mass transfer coefficient and pressure drop were determined for different configurations and operations of the micromixer. When the two fluids are first partitioned into sub-streams and impinging in opposite directions, and the mixing chamber has also an arborescent structure, the mixer (T-M) has a superior performance when the gas feeding rate is sufficiently high. For a small gas feeding rate, the mixer (J-M-G) will have a higher mass transfer coefficient if the gas is introduced from the center plate, which was used as the mixing chamber in T-M, but at the cost of larger pressure drop when compared with T-M. T-M has the best performance under all operating conditions if both mass transfer coefficient and pressure drop are taken into account. (C) 2010 Elsevier By. All rights reserved.