Formation and Transport of Bubbles in Microfluidic Systems

Precise manipulation of minute volumes of fluids is at the heart of microfluidics and opens up an exciting route to miniaturize processes in the areas of chemistry, biology and medicine. An attractive way to transport small fluid samples through the channels of microfluidic devices is by enclosing these samples inside containers in the form of microbubbles or microdroplets. The work described in this thesis is motivated by the need to reliably form such microbubbles and microdroplets and robustly transport them through networks of microchannels at high throughput. One of the central questions addressed in this thesis is how bubbles form at T-junctions under conditions typical to bubble-based microfluidic systems. The basic question how large bubbles grow is resolved by studying the fundamentals of bubble formation and pinch-off using experimental techniques, such as micro Particle Image Velocimetry. Another key question addressed in this thesis is how bubbles are transported in confined geometries. We hereby considered transport of bubbles through simple microchannel networks as found in for instance micro reactors and laboratories-on-chips, as well as through more complex microchannel networks comparable to for instance the pore structure in micro packed beds or oil reservoirs.Multi-Scale Physics / Chemical EngineeringApplied Science