Yee, Yao-Chung (2007-08). Novel design of a passive microfluidic mixer for biochemical reactions and biosensing. Master's Thesis.
The next step in miniaturization of analytical devices involves the use of MEMS and Lab-on-a-Chip applications, where many biological or chemical reactions are carried out on the device in real time. Since detection mechanisms occur almost immediately after the reactions, inefficient mixing of reagents could cause a decrease in sensing capability, especially on micro- and nano-scaled devices. Thus a microfluidic mixer has become a crucial component in these applications. Here we propose a new design of a passive microfluidic mixer that utilizes the theories of chaotic advection to enhance mixing. The micro-channels for the mixer have dimensions with width ranging from 10um to 40um, depth 40um, and a total length of 280um. First the designs are simulated using CFD-ACE+ for computational analysis. After the device geometry has been decided, the actual devices are fabricated using traditional UV photolithography on silicon and bonded with pyrex glass by anodic bonding. To test the actual device mixing efficiency, we used a fluorescent dye rhodamine B solution to mix with DI water and put the devices under fluorescent microscope observations for real-time analysis. Images of fluorescent light intensities are taken at different flow rates during the analysis and are later used to study the experimental results calculated using a published mixing efficiency formula for comparison.