Microfluidic systems (lab-on-a-chip devices) are employed in micro-technology having applications in protein and DNA analysis, sensors, and micro electronics mechanical systems. These systems operate in a pressure driven flow regime with no moving parts to drag the fluids. Our research aims at developing rigorous assessment and quantification of mixing in microchannels. The work presented is based on numerical simulations of flow in different geometries coupled with mixing assessment using entropic measures. The results show enhanced mixing efficiency for the geometry similar to the staggered herringbone mixer by comparison with a mixer with straight diagonal ridges and lack of mixing in a non-patterned channel.