The physics of micro/nanofluids has become an area of intense interest both scientifically and technologically. The long-range nature of viscous flows and the small dimension inherent in confined spaces imply that the influence of boundaries is quite significant. Among the boundary effects, we should focus on the hydrodynamic slip at a solid-liquid interface and the electrokinetic phenomena. The flow enhancement will benefit during the transport, since friction increases with the surface-to-volume ratio. We first provide the explicit model for rectangular microchannels with solvophobic smooth surfaces. The external body force originated from between the Poisson-Boltzmann field and the flow-induced electric field was employed in the Navier-Stokes equation taking into account the Nernst-Planck principle. The slip length was obtained with the particle streak velocimetry using dilute colloids with variations of the shear rate and suspension pH. The wettability increases by the introduction of surface charge, therefore, the slip length has a trend to decrease as the pH increases. When the fluid slip is absent, a higher friction factor would be predicted in view of the electroviscous effect. Further, we consider the electrokinetic flow in the serpentine channel, and resultant velocity profiles are computed with variations of geometry curvature and electric surface potential.
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: 370 - 373
Industry sectors: Medical & Biotech | Sensors, MEMS, Electronics
Topics: Micro & Bio Fluidics, Lab-on-Chip