A passive micromixer with gaps and baffles was proposed based on the principle of chaotic mixing and the fluid flow and mixing characteristics in the micromixer were studied by three-dimensional numerical simulation and visualization experiment. Expanded vortices and separated vortices were generated in the horizontal plane and counter-rotating vortices formed in the cross-sectional plane perpendicular to the flow direction by the combination of gaps and baffles. The mixing efficiency was significantly improved by the multidirectional vortices. The geometrical parameters of gaps and baffles had great effect on the fluid flow and mixing. Based on the consideration of mixing efficiency and pressure drop

the effect of gap width

gap length and baffle height on the comprehensive performance of the micromixer was investigated by the field synergy principle. The optimal structural parameters were presented with varying Reynolds number.