Fluid Mixing Online and In Microdevices

Microfluidics and polymer MEMS are the most promising technologies to realize biochemical analysis systems on a chip with low cost, tiny fluid sample, fast chemical/biochemical reaction, and high detection accuracy capabilities. Sample processing, chemical/biochemical reaction, and sample detection are considered as the three major tasks required for lab-on-a-chips. Micropumps, microvalves and micromixers are also considered as key components in handling microfluidics in the lab- on-a-chips. There have been numerous efforts to develop on-chip active micropumps and microvalves. However, the realization of active microfluidic components in an on-chip disposable platform has been considered as one of the most difficult tasks in terms of fabrication, system integration, reliability, and cost. Consequently, the development of passive microfluidic components is a good alternative to the active components if they can provide the same level of functionality. In this research, passive mixing using geometric and initial conditions variations in microchannels were studied due to its advantages over active mixing in terms of simplicity and ease of fabrication. Because of the nature of laminar flow in a microchannel, the geometric variations were designed to improve lateral convection to increase cross-stream diffusion. Previous research using this approach was limited, and a detailed research program using computational fluid dynamic (CFD) solvers, various shapes, sizes and layouts of geometric structures was undertaken for the first time. Mixing efficiency was evaluated by using mass fraction distributions. Different types of geometric and initial conditions variations were researched. First, Structures were used to investigate the effect channel geometry on fluid mixing and flow patterns. Secondly, we applied different initial velocity in each inlet to see the effect of Reynolds number applied on mixing behavior. Third, we applied different kind of fluid in each inlet to visualize the effect of viscosity and finally we create new split and stair geometries to enhance the mixing efficiency.