Electroosmotic flow of viscoelastic fluid through a constriction microchannel

Abstract

Electroosmotic flow (EOF) has been widely used in various biochemical microfluidic ap-plications, many of which use viscoelastic non‐Newtonian fluid. This study numerically investigates the EOF of viscoelastic fluid through a 10:1 constriction microfluidic channel connecting two reser-voirs on either side. The flow is modelled by the Oldroyd‐B (OB) model coupled with the Poisson– Boltzmann model. EOF of polyacrylamide (PAA) solution is studied as a function of the PAA concentration and the applied electric field. In contrast to steady EOF of Newtonian fluid, the EOF of PAA solution becomes unstable when the applied electric field (PAA concentration) exceeds a critical value for a fixed PAA concentration (electric field), and vortices form at the upstream of the constriction. EOF velocity of viscoelastic fluid becomes spatially and temporally dependent, and the velocity at the exit of the constriction microchannel is much higher than that at its entrance, which is in qualitative agreement with experimental observation from the literature. Under the same ap-parent viscosity, the time‐averaged velocity of the viscoelastic fluid is lower than that of the Newtonian fluid.