Simultaneous Pumping and Mixing of Biological Fluids in a Double-Array Electrothermal Microfluidic Device

Alinaghi Salari,Colin Dalton

doi:10.3390/mi10020092

Abstract

Transport and mixing of minute amounts of biological fluids are significantly important in lab-on-a-chip devices. It has been shown that the electrothermal technique is a suitable candidate for applications involving high-conductivity biofluids, such as blood, saliva, and urine. Here, we introduce a double-array AC electrothermal (ACET) device consisting of two opposing microelectrode arrays, which can be used for simultaneous mixing and pumping. First, in a 2D simulation, an optimum electrode-pair configuration capable of achieving fast transverse mixing at a microfluidic channel cross-section is identified by comparing different electrode geometries. The results show that by adjusting the applied voltage pattern and position of the asymmetrical microelectrodes in the two arrays, due to the resultant circular flow streamlines, the time it takes for the analytes to be convected across the channel cross-section is reduced by 95% compared to a diffusion-only-based transport regime, and by 80% compared to a conventional two-layer ACET device. Using a 3D simulation, the fluid transport (pumping and mixing) capabilities of such an electrode pair placed at different angles longitudinally relative to the channel was studied. It was found that an asymmetrical electrode configuration placed at an angle in the range of can significantly increase transversal mixing efficiency while generating strong longitudinal net flow. These findings are of interest for lab-on-a-chip applications, especially for biosensors and immunoassays, where mixing analyte solutions while simultaneously moving them through a microchannel can greatly enhance the sensing efficiency.

Highlights

Microscale fluid manipulation techniques have received much attention over the last decade due to the wide range of applications in various research fields including medicine, chemistry, and biology [1,2,3]
If the orientation of the array is set such that microelectrodes are placed parallel to the microfluidic channel, the AC electrothermal (ACET) microvortices will be mostly dragging the liquid on the cross-sectional plane of the channel
If the microelectrode pairs are rotated 90◦, such that they become perpendicular to the channel length, the resultant ACET microvortices will only drag the liquid along the channel, and a net flow will be generated

Summary

Introduction

Microscale fluid manipulation techniques have received much attention over the last decade due to the wide range of applications in various research fields including medicine, chemistry, and biology [1,2,3]. One major challenge in microfluidic devices is the manipulation of fluids and droplets effectively in such scales. Due to the laminar flow regime (i.e., low Reynolds number) in microfluidic devices, mixing of species is difficult and unless an active mixing strategy is employed, passive diffusion is the only mechanism that causes the fluid to mix. Physical actuators or mechanical parts (e.g., diaphragm and check valves) are utilized in order to generate a pressure difference across a liquid bulk. For the special case of pumping electrically conductive fluids (i.e., electrolytes), electrokinetic techniques are more effective. The application of electrokinetics in the development of microfluidic devices has attracted great attention over the past decades, owing to its fairly simple implementation and reliability due to no moving parts [10]

Methods

Results

Conclusion