Thermal and rheological investigation of non-Newtonian fluids in an induced-charge electroosmotic micromixer

Abstract

Microfluidic devices have drawn many researchers in the various fields of area such as biomedical diagnostics, biological and chemical analysis. Among these applications, micromixing has a prominent impact on the efficiency and sensitivity of microfluidic devices. In this study, an induced-charge electroosmotic solver with the presence of Joule heating effects has been developed in the open-source code package, OpenFOAM, to investigate the rheological effects of non-Newtonian fluids in a trapezoidal micromixer. The mathematical model and the developed solver are validated with existing data in the literature and the effects of micromixer geometry, various applied DC electric potential, rheological effects of fluid and the heat transfer are studied to attain an efficient micromixer. Results show that the proposed micromixer offers the advantages of high mixing efficiency with a high flow rate in comparison to other investigated geometries. Newtonian, Shear-thinning, and shear thickening fluids are studied in this article and it is shown that in Newtonian fluid and shear-thinning fluid, the mixing efficiency is enhanced by amplifying the applied electric field which can be concluded that the effects of vortices have more impact on mixing efficiency in comparison to the flow rate. On the other hand, in shear thickening fluid, the mixing efficiency is decreased by amplifying the electric field, because the flow rate is enhanced which leads to the increment of fluid viscosity and decrement of the strength of vortices. Finally, to analyze the fluid temperature rising because of the presence of Joule heating, the heat transfer is studied to assure the health of cells in the proposed micromixer.