Discrete Mixing of Nanoliter Drops in Microchannels

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We present the theory, simulations and experiments for discrete drop mixing in microfluidic systems. The generalized analytical solutions have been derived and confirmed by simulations and on-chip experiments. The discrete drop mixing occurs in three different regimes (diffusion, dispersion, and convection-dominated) depending on various operational parameters collectively expressed by the Péclet number (Pe= Ud d/D) and the drop dimensions. Introducing the modified Péclet number (Pe*=Pe d/L), we present asymptotic curves to predict the mixing time and the required drop displacement distance for mixing at a given Pe*. COMSOL simulations and on-chip experiments were performed to verify the theoretical limits. The simulated mixing results for the three different regimes show distinctly different mixing behaviors as predicted in the theoretical modeling. In our experimental work, we used a PDMS microchannel with a unique membrane air bypass valve (MBV) to precisely control the mixing and merging site. Finally, we show that experimental, simulation, and theoretical results all agree and confirm that mixing can occur in fractions of a second to hours. The presented work guides understanding of discrete drop mixing and show that efficient mixing in microfluidic systems can be achieved in a simple mixing scheme.

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Journal: TechConnect Briefs
Volume: 3, Nanotechnology 2008: Microsystems, Photonics, Sensors, Fluidics, Modeling, and Simulation – Technical Proceedings of the 2008 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: June 1, 2008
Pages: 300 - 303
Industry sectors: Medical & Biotech | Sensors, MEMS, Electronics
Topics: Micro & Bio Fluidics, Lab-on-Chip
ISBN: 978-1-4200-8505-1