Mixing based on mass diffusion and advective flow at low Reynolds number is important on design of microscale vortex generators. We studied on the optimization of micromixer for the improvement of mass transport using an advanced response surface method to be closely approximate the real map of mixing performance. We considered four rib geometries simultaneously; rib angle, rib height, rib width, and rib spacing. The optimized microchannel was occurred at a micromixer configuration where theta, d/h, a/d, and b/d were 35.6 degrees, 0.7, 0.127, and 1.10, respectively. The channel length to obtain the mixing uniformity over 95% was 1344 mu m (C) 2010 Elsevier Ltd. All rights reserved.