The fluiddriven efficiency of the micropump based on induced charge electroosmotic was studied by numerical simulation method. In this paper, we propose to make some improvement against the Tshaped piping design of micropump, and we embed a janus cylinder in the junction of the Tshaped pipe for the micropump design. We offer different voltage to the inlet of the pipe and carry out the numerical study of the fluid field induced by the cylinder, and the comparison of the velocity and flux of the outlet in different voltage as carried out. It is found that there are two symmetrical circulations around the polarizable side of the cylinder. And the comparison results show that the flow and the velocity of the outlet were increased with the increasing voltage of the entrance.
The development of microfluidic system raises the fundamental question of how to achieve good microfluid transmission and drive results [
However, there are some shortcomings for electroosmosi. For example,
In comparison with EOF, the velocity of ICEOF may be higher because of its nonlinear dependence on the applied electric field. Those unique characteristics may lead to new applications in microfluidics and nanofluidics. Recent research includes using ICEOF for mixing [
In general, the induced charge electroosmosis (ICEOF) could be used for the design of micropump in microfluidic system. The impetus of this paper is to advance the understanding of induced charge electroosmosis (ICEOF) around a Janus cylinder in a confined Tshaped microchannel, and it is mostly concerned with the design of a super efficient Tshaped micropump. The relationship between fluid field and extra electric field is also studied in this research.
The design of the Tshaped micropump with a Janus cylinder is shown in Figure
Schematic diagram of the Tshaped microchannel with Janus cylinder.
The mesh used in numerical simulation.
For the design of the Tshaped micropump, we study the ICEOF around the Janus cylinder, and the model parameters are shown in Table
Model parameters.
Parameter  Value  Description 


100 
The distance between inlet1 and inlet2 

20 
The width of the microchannel. 

10 
The distance between cylinder center and side wall. 

50 
The length of vertical pipe of Tshaped microchannel. 

10 
The diameter of the Janus cylinder. 
Assuming the flow is incompressible and steady and driven by the ICEOF, the momentum equation of flow can be given as
Based on the property of flow field, two velocity components are described by
In general, ion concentration is affected by both the distribution of the externally applied potential,
For fluid flow, atmospheric pressure is specified at the inlet and outlet, and there is no slip boundary condition on the wall. For external potential, a constant value for potential is specified at the inlet and outlet, and its normaldifferential value on the wall is zero. For EDL potential, its normaldifferential value on the inlet and outlet is zero. Now, we will discuss the surface electric potential in detail.
Standard electric flow contains the interaction between the external electric potential and the fixed electric double layer. Thus, the electroosmotic flow velocity is linearly dependent with the external electric field strength. However, when the solid surface is polarizable and conductive, the interrelation between the two will be very different. In this case, the induced zeta potential
We choose the controlvolumebased method to solve the equations, and a specific discrete method is used to get the secondorder accuracy. Firstly, we solve (
Evaluating the induced zeta potential around conducting surface is critical to calculate ICEOF, and for 2D circular cylinder, our numerical scheme has been validated by the comparison with the analytical formulation that has been derived (Bazant & Squires [
Schematic diagrams of induced zeta potential distribution on the polarizable particle’s surface.
The present simulation assumes that the Tshaped microchannel is made of silica glass. And it is assumed that waterliquid is used as the working fluid and its physical properties are given by
In this investigation, the microchannel has an external electric potential of
As previously stated, when the conducting cylinders are immersed in the electric field, a nonuniform distribution of zeta potential will be induced on the conducting surfaces, causing a varying driving force of the electroosmotic flow. Consequently, the slipping velocity on the conducting surfaces changes with position, resulting in a nonuniform flow field. Due to the oppositely charged surfaces, flow circulations are generated near the conductive side of the embedded cylinder.
Here, we offer the flow diagram around the Janus cylinder when
The flow diagram around the Janus cylinder when
The flow diagram around the Janus cylinder when
For better study of the relationship between external electric field strength and the Tshaped pump driven efficacy, we make numerical simulation when
The velocity magnitude profiles under different applied electric field.
The flux at the outlet of the microchannel under different applied electric field.
In summary, the Tshaped micro pump embedded a Janus cylinder, and we propose in this paper that good fluiddriven efficiency can be obtained under small external electric potential, which is of practical value.
In this paper, we offer a design of Tshaped micropump that embedded a Janus cylinder. We carry out the numerical study of the fluid field induced by the cylinder and make comparison between the velocity magnitude and flux of the outlet in different voltage. It is found that there are two symmetrical flow circulations around the polarizable side of the Janus cylinder, and they can be used to improve the driven efficiency of the pump. The dependence of the driven efficiency on the electric field is also predicted. The conclusions above can be utilized for the optimization of the design of microfluidic devices.
The authors are extremely grateful to the editor and the anonymous reviewers for their constructive and valuable comments, which have contributed much to the improvement of this paper. Also, the authors gratefully acknowledge the financial support from the National Natural Science Foundation of China with Grant no. 10902105 and the Natural Science Foundation of Zhejiang Province with Grant no. Y6090406/2010R10014.