Breakup of confined droplets in microfluidics

Abstract

Segmented-flow microreactors have emerged as an attractive tool for fine chemical synthesis and (bio)chemical analysis, owing to their high heat and mass transfer rate, low axial dispersion, as well as rapid mixing. A key challenge for the use of segmented-flow microreactors in large-scale processing is their low throughput. This can be overcome by applying the concept of numbering-up in which several microreactors are placed and operated in parallel. A challenging aspect of this approach is to distribute segmented flows over those parallel microreactors with a high uniformity in the size and the speed of the fluid compartments. In this thesis, we propose to use a bubble-splitting distributor where a single stream of fluid compartments is recursively split into smaller ones via a series of T-junctions. We first investigate the fundamental physics of the breakup of droplets in a single T-junction using CFD simulations. Being able to explain the mechanism of the droplet breakup leads us to a more applied question, how to design a bubble/droplet distributor and what are the optimum operating conditions. We present theoretical and experimental analyses of the uniformity of the distribution of bubbles/droplets using the proposed distributor and provide guidelines to operate it for different flow conditions. The thesis ends with a discussion on how some of our main findings can be generalized and opportunities for future research.