Abstract
The Lattice Boltzmann-electrohydrodynamic approach is proposed to study the dynamics of electrowetting-on-dielectric-driven microdroplet transport. We apply the pseudo-potential lattice Boltzmann model to study the dynamic process of droplet motion and introduce a new distribution function to solve the Laplace equation to predict the electric field distribution. The EWOD effect is numerically analyzed to verify the validity and versatility of the method. Then, the electric potential distribution and the changes of the droplet morphology, droplet edges and contact angles over time are studied. Additionally, we investigate the effects of the crucial factors, including the electrode switching frequency, applied voltage and droplet viscosity, on droplet motion. The numerical results agree well with the theoretical values and experimental results from the literature.
Highlights
The LB-EHD method that couples the flow field and the electrostatic field is proposed to study the dynamics of droplet motion induced by EWOD in an electrohydrodynamic framework
The dynamic behavior of droplets is studied by applying the pseudopotential model of the lattice Boltzmann method (LBM) and the electric field distribution is predicted by introducing a new distribution function
We studied the electric field distribution, the change of the droplet morphology, and the droplet edges and contact angles over time
Summary
With the advancement of micromachining and precision manufacturing, micro-electromechanical systems (MEMS), especially microfluidic systems, have become the most popular subject. Digital microfluidic systems (DMS), in which individual droplets are used instead of continuous flows, have shown great potential in biochemical and biomedical applications including enzyme assays, cell assays, immunoassay, DNA and protein analysis. In digital microfluidic devices, several techniques for handling droplets have been developed, such as thermal or chemical modulation of liquid surface tension as well as electrostatic control of contact angles, including dielectrophoretic (DEP) and electrowetting-ondielectric (EWOD). Among these methods, EWOD is the most promising one because of the advantages of fast response, real-time actuation, good stability and low power consumption. Droplets can be flexibly manipulated on a programmable electrode array for transmission, merging, and splitting. experiments on droplet dynamics at the micro-scale are difficult and costly, and analytical models do not generally provide transient information on droplet motion. Several techniques for handling droplets have been developed, such as thermal or chemical modulation of liquid surface tension as well as electrostatic control of contact angles, including dielectrophoretic (DEP) and electrowetting-ondielectric (EWOD).13 Among these methods, EWOD is the most promising one because of the advantages of fast response, real-time actuation, good stability and low power consumption.. A LB-EHD method that couples the flow field and the electrostatic field is proposed to investigate the dynamics of EWOD-induced droplet motion in the framework of electrohydrodynamics This method provides a more direct description of the electric force driving the droplet than the thermodynamic energy minimization-based method, which is governed by the Young-Lippmann equation. Our proposed method can be used to describe the motion of dielectric liquids and to reveal the contact angle saturation behavior observed in experiments
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