Numerical simulation of fluid flow and mass transfer in micro-fluidic devices.

摘要

The design of microfluidic systems for use in biochemical analysis and research require a good understanding of fluid behavior at low Reynolds numbers, where channel size and operating flow speed are extremely small. Electrically driven flow (Electroosmosis) is an alternative to pressure driven flow in micro-channels. The numerical methods and solution procedures for both pressure and electroosmotically driven flows are described. Steady electroosmotic flows sometimes satisfy “Ideal Electroosmosis” criteria making it much simpler to compute the flow.; Simulations are carried out to trace transient dye propagation in a straight channel followed by a downstream circular well and these simulations are compared with the experiments. Using similar simulation and experimental techniques, composition modulation in time using a Y-shape channel junction is simulated and experimented to investigate the limiting modulation frequency. The modulation regime is divided into two categories, and the results show that for a given channel dimension the desired modulation of the solution composition is only possible below a certain non-dimensionalized threshold frequency.; Microfluidic channels patterned with non-uniform zeta potentials do not satisfy “Ideal Electroosmosis” conditions. With thin electric double layer assumptions, the flows in patterned channels are investigated numerically using Navier-Stokes equations with Helmholtz-Smoluchowski wall-slip boundary conditions. For a two dimensional flow, vortex center location and flow rates are investigated for various geometrical parameters of the channel. In three-dimensional flow simulations, the generation of a net vortical motion (equivalent to that produced by a vortex aligned with the flow direction) is investigated and applied to chaotic mixing using herringbone pattern. The mixing performance is measured through the estimation of standard deviation with particle track data. Through numerical simulation, the feasibility of the microfluidics mixer using patterned zeta potential is verified.