We present the first transient pressure measurements and high-speed visualizations of a gas bubble passing through liquid-filled microchannel contractions. Results are compared with a simple theoretical model taking into account the Young-Laplace pressure drop, the channel geometry and wetting properties. Good agreement is obtained for the transient shape and value of the pressure drop, and discrepancies are explained by additional effects such as wettability, contact line pinning, bubble instability and viscous pressure drop.
The motivation of this study is to understand and control the motion of gas bubbles in microfluidic devices, using device geometry, surface properties and flow pattern. While some devices rely on the presence of bubbles such as chemical reactors, emulsions generators or micropumps using bubbles as actuators, in many cases the challenge is to suppress unwanted bubbles generated by cavitation, electrochemistry, or priming (filling) of the microchannels, since they perturb the function of valves, tree-branching, or nozzles.
Journal: TechConnect Briefs
Volume: 2, Technical Proceedings of the 2006 NSTI Nanotechnology Conference and Trade Show, Volume 2
Published: May 7, 2006
Pages: 497 - 500
Industry sectors: Medical & Biotech | Sensors, MEMS, Electronics
Topic: Micro & Bio Fluidics, Lab-on-Chip