A passive microfluidic mixer with high performance is designed and fabricated in this work. Diamond-shaped obstacles
were chosen to split the flow into several streams, which are then guided back together after the obstacle. To keep
pressure drop low, the channel cross-sectional area was maintained equal to the input cross-sectional area, and this was
held constant throughout the device. The proposed design was modeled using computational fluid dynamics (CFD)
software. The effects of channel width, channel length, location of obstructions, and Reynolds Number (Re) were
investigated. The simulated results were verified experimentally. Simulation data showed that the designed micromixer
achieved 90% mixing at a channel length of 4.35 mm with pressure drop of 584 Pa at Re = 1, while experimental data for
Re = 0.1 showed 90% mixing at 7 mm. The mixer functions well especially at the low Re (Re = 0.1).
Fluorescently labeled beads may be utilized in transparent microfluidic devices to facilitate a variety of immunoassay based chemical measurements. We investigate the ability to visualize, quantitate, and reduce undesirable adsorption of beads within a polydimethylsiloxane (PDMS) microchannel device. These methods are prerequisites to the design of practical bead-based microfluidic sensing devices. The PDMS microchannels were shown to be transparent enough to make accurate quantitative optical measurements, although significant adsorption was observed. Epifluorescence microscopy was employed in an attempt to quantitatively evaluate microbead adsorption to PDMS microchannel walls and bulk surfaces after different agitation, solution, and surface treatments. This microscopy method provides reproducible imaging of individual beads and allows for characterization of adsorption to PDMS microchannel walls. Solution composition seemed to play a more important role in the ability to reduce the number of adsorbed beads to the PDMS surface than agitation. The most significant reduction in bead adsorption was seen in surface treatment. The most effective surface treatment examined in this study was Teflon AF.