Microfluidics is the science and technology of systems that manipulate fluid volumes in a range of picoliters and microliters in channels from 100 nm to 1 mm. Microfluidics focuses on developing design methods and manufacturing miniaturized devices that have as their main advantages the reduction in sample consumption, automatic analysis, high sensitivity, portability, short reaction times, and low processing costs. In this way, microfluidics can be considered as a tool that addresses a series of limitations imposed by conventional macroscopic methods. Due to the exponential increase in research in miniaturization and the applications of microfluidics, the importance of a continuous understanding of the theory and mechanisms governing mixing tasks at the micrometer level should be highlighted. In this context, a rapid and accurate preparation of a mixture could be necessary for many applications in the biological, medical, and chemical areas, for agent detection, analytical assay, organic synthesis, cell activation and analysis, enzyme reactions, protein folding, drug delivery, among others. Hence, micromixers are one of the most important devices in microfluidic systems. For some of these micrometer-scale applications, the mixing process is very slow due to the laminar flow regime present. In this context, mixing in laminar flows is related to molecular diffusion. In the absence of turbulence, it is not possible to obtain a rapid and good mixture by molecular diffusion without increase too much the contact space. For this reason, the scientific community has studied different designs of electrokinetic micromixers for efficient mixing. Therefore, to increase knowledge about the mixing process in microfluidic devices, this paper presents the 2-D numerical solution of the flow and concentration field of an electrokinetic T-type micromixer, under heterogeneous zeta potentials modulated via sinusoidal functions and interfacial viscoelectric effects. Here, the viscoelectric effects appear to modify the fluid viscosity due to the high voltages within the electric double layer. The mathematical model is based on the Poisson-Boltzmann, mass conservation, momentum, and species concentration equations. In the steady-state analysis, two electrolytes with known ionic concentration and an imposed velocity profile are considered at the inlet of the micromixer. The results demonstrate that by using heterogeneous zeta potentials, at the mixer walls, generated flow recirculations along the mixer channel, promoting the rise in mixing efficiency; however, for high zeta potential values, this is counteracted by the viscoelectric effects. The present investigation shows how the viscoelectric condition deteriorates the mixing performance and how with the correct selection of modulated zeta potential parameters as the wavenumber, and the phase angle can improve it. Therefore, the performance of the mixer studied here should be considered for the design of microfluidic devices in the future.


Numerical Analysis of a T-Type Electrokinetic Micromixer With Heterogeneous Zeta Potentials and Viscoelectric Effects

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

IMECE2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.