Simulation of the Slip Velocity Effect in an AC Electrothermal Micropump.

Fraj Echouchene,Thamraa Al-Shahrani,Hafedh Belmabrouk

doi:10.3390/mi11090825

Abstract

The principal aim of this study was to analyze the effect of slip velocity at the microchannel wall on an alternating current electrothermal (ACET) flow micropump fitted with several pairs of electrodes. Using the finite element method (FEM), the coupled momentum, energy, and Poisson equations with and without slip boundary conditions have been solved to compute the velocity, temperature, and electrical field in the microchannel. The effects of the frequency and the voltage, and the electrical and thermal conductivities, respectively, of the electrolyte solution and the substrate material, have been minutely analyzed in the presence and absence of slip velocity. The slip velocity was simulated along the microchannel walls at different values of slip length. The results revealed that the slip velocity at the wall channel has a significant impact on the flow field. The existence of slip velocity at the wall increases the shear stress and therefore enhances the pumping efficiency. It was observed that higher average pumping velocity was achieved for larger slip length. When a glass substrate was used, the effect of the presence of the slip velocity was more manifest. This study shows also that the effect of slip velocity on the flow field is very important and must be taken into consideration in an ACET micropump.

Highlights

Alternating current electrokinetics (ACE) such as AC electrothermal (ACET), AC electro-osmosis (ACEO), and dielectrophoresis (DEP) are a promising technology for development in lab-on-a-chip systems and Bio-MEMS [1,2,3,4,5,6,7]
Selmi and Belmabrouk [11] investigated the repercussions of the AC electroosmosis force on a microfluidic biosensor
The effect of the slip velocity is very significant with a rate of increase of 33%

Summary

Introduction

Alternating current electrokinetics (ACE) such as AC electrothermal (ACET), AC electro-osmosis (ACEO), and dielectrophoresis (DEP) are a promising technology for development in lab-on-a-chip systems and Bio-MEMS [1,2,3,4,5,6,7]. Zhang et al [24] investigated a two-phase ACET micropump fitted with a coplanar asymmetric electrode array Using this device, the fluid flow rates can be 50% faster than those obtained with a single-phase structure. Gao and Li [25] studied an ACET micropump integrating an asymmetric spiral microelectrode pair in a cylindrical microchannel in order to drive rapidly and to mix efficiently, high-conductivity fluids. Salari and Dalton [27] introduced a double-array ACET equipment involving two opposite microelectrode arrangements This device can be used for simultaneous pumping and mixing. The numerical study considers slip and no-slip boundary conditions These models have been used to investigate an ACET flow micropump having asymmetric planar electrode pairs and using slip and no-slip boundary conditions. The effects of frequency, voltage, concentration, and substrate material under slip velocity at the wall of the microchannel were discussed

Physical Configuration

Physical Model

Effects of Slip Velocity and Thermal Conductivity on Average Pumping Velocity

Findings

Conclusions