Study On Flow Behavior Of Periodical Electroosmosis In Microchannel For Biochips

Electroosmosis has been widely used in fields of biochemistry and medicine. Electroosmotic pumps and capillary electrophoresis are important elements in biochips and micro-total -analysis system.This paper investigates general flow behavior of periodical electroosmosis in microchannels based on Poisson-Boltzmann equations for electric double layer (EDL) and Navier-Stokes equation for incompressible viscous fluid.Most studies solved periodical electroosmosis separately inside EDL and outside EDL. The flow inertia, has been ignored inside EDL. This paper solves Navier-Stokes equations for an analytic solution of periodical electroosmosis in a united region including EDL and outside EDL of microchannel, reserving complete flow inertia.In this paper an analytical solution for periodical electroosmotic flows with arbitrary Reynolds number in two-dimension uniform microchannel is present by solving the dimensionless equations. An asymptotic solution for low Reynolds number is obtained. Finite difference results, which agree well with the analytical solutions, are also carried out.The flow behavior of periodical electroosmosis in three-dimensional microchannel with a rectangular section is also investigated ,and a finite element -iterative algorithm is employed to solve the equations .The results presented in this work indicate that the velocities of periodical electroosmosis strongly depends on Reynolds number, as well as on EDL properties and applied electric field. In the cases of low Reynolds number periodical electroosmosis has the same velocity amplitude and a plug-like velocity profile as that of the steady electroosmosis. In the cases of high Reynolds number electroosmosis velocity outside the EDL decreases, and lag phase angle of velocity increases as the distance from the channel wall increases. A wave-like velocity profile, in 2D cases, and a bowl-like velocity profile, in 3D cases, are found in this study. Furthermore, the velocity profile varies periodically with time. The slip velocity of EDL and transient flow rate of the microchannel decreases as the Reynolds number increases.