Gas-liquid segmented flow microfluidic reactors

• Main Author: Kazemi Oskooei, Seyed Ali
• Other Authors: Sinton, David A.
• Language: English; en
• Published: 2010
• Subjects: Segmented flow microreactors; Microfluidics; UVic Subject Index::Sciences and Engineering::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/1828/2582

This thesis is devoted to the study and application of gas-liquid segmented flow microfluidic reactors. In the most common configuration, these devices facilitate mixing and reaction of liquid-phase constituents by the introduction of non-participating gas bubbles in a microchannel flow. In this work, segmented flow microreactors are modelled, designed, fabricated, tested and applied. Residence time distribution (RTD) within the reactors is employed as a measure to quantify reactor performance. In order to narrow the residence time distribution, a novel microreactor with hybrid surface properties is developed. The injector channel is made wetting to the liquid phase to assure stable segmentation while the reaction channel is rendered less wetting to eliminate the lubricating film surrounding the gas bubbles. It is demonstrated through RTD testing that the hybrid microreactor shows up to 63% gain in performance over the fully-wetting reactor. A numerical model is developed to study the feasibility of shear-induced breakup of nanoparticles within gas-liquid segmented flow reactors. The critical shear rate required for breakup is calculated from literature and is compared to the maximum shear rate value found through modeling to give a prediction for the possibility of particle breakup. Previous experimental data support the existence of shear-induced particle breakup. Here, the transition region where the liquid film meets the liquid plug is found to exhibit relatively high shear stresses. With these results, the potential role of shear-induced processing of nanoparticle systems is discussed. Lastly, fabricating devices with long microchannel lengths, as required in this work, necessitates the ability to densely pattern microfluidic channels on a substrate with minimal defects. The fabrication methods developed and employed here for densely patterned, high surface area microchips are presented in detail. These microchips were employed in this thesis work and also in other collaborative works.