Investigation of Visco-rheological Properties of Polymeric Fluid on Electrothermal Pumping

Electrothermal pumping is a recently trending method to force highly conductive fluids in a wide range of microfluidics applications with biological processes. Although most polymer fluids (biological and synthetic) are highly conductive exhibiting viscoelastic rheological properties that are relevant to biomedical applications, their behavior under the effect of electrothermal force has not yet been studied. To this aim, the PTT model (non-linear rheological constitutive equation) and electrothermal equations are implemented in the developed OpenFOAM solver. The effect of rheological characteristics of the fluids on the physical parameters such as velocity, elastic behavior, and vortices strength of electrothermal flow are investigated through the viscoelastic non-dimensional numbers. According to the results, electrothermal outlet velocity decreases by 726% as the retardation ratio (beta number) increases from 0.2 to 0.9 and increases by 107% as the Weissenberg number raises from 0.001 to 10. Investigating all non dimensional numbers simultaneously leads to the conclusion that higher electrothermal velocity is achieved by viscoelastic fluids with lower viscosity and higher relaxation time. This fact is useful for choosing the proper fluid for a particular application. As a practical example, 3000 ppm polyethylene oxide solution results in higher velocity in electrothermal flow compared to the 5% polyvinylpyrrolidone and 2000 ppm xanthan gum solution.