In this project, I have provided detailed information on the design, simulation, fabrication and characterization of an inplane passive micromixer capable of mixing at low Re. The micromixer was designed using COMSOL CFD software and fabricated in PDMS. Detailed study of the various design parameters and their effect on the mixing efficiency of the micromixer was provided. The effect of Reynolds number on the mixing efficiency of the micromixer was observed and determined that the device performs better at lower Reynolds numbers and agrees with the observations made by Bhagat et al. This also confirms the observation made by Nguyen and Wu that the performance of the micromixer is very closely related to the Reynolds number of operation. Difference between the CFD model and experiments was observed and can be attributed to the fabrication technique of the micromixer and the lack of sufficient computational resources for modeling the device. Finally, the design discussed in this report is easy to fabricate, has low pressure drop along the micro channel allowing for easy integration and use with more complex lab-on-a-chip applications.