Study On Electro-osmotic Mixing Of Fluid In T-shaped Micro-mixer Under Periodic Potentials

As an emerging technology,microfluidic technology is playing a more and more important role in fields of MEMS,micro-fluid machinery,biomedicine,new drug synthesis and screening etc..As one of the indispensable components of microfluidic system,the mixing efficiency of a micro-mixer determines the performance of the whole system.In this paper,the active electro-osmotic micro-mixer is selected as the research object,and its mixing process is numerical simulated by COMSOL Multiphysics software.The detailed work and achievements are as follows:Firstly,the application background and research status of micro-mixer are introduced.The research of collide and mixing process of two streams in a T-shaped micro-mixer are summarized.What is more,A micro-mixer is alternatively a passive micro-mixer or an active-micro one and both of their principles and previous studies are included.Then,theories of the simulation of electro-osmotic mixing are analyzed.The principles and constraint equations of flow field,concentration field and the effect of electric double layer are introduced.In order to evaluate the mixing ability of a micro-mixer quantitatively,the algorithm of mixing efficiency is stated.Next,three types of periodic potentials are applied on the electrodes fixed to the wall of a T-shaped micro-mixer.Mixing process and efficiency in different cycle of T are obtained.It is concluded that mixing efficiency fluctuates with the time when T is relative larger and the fluctuation decreases until disappear when T turns smaller.Overall,mixing efficiency first rises and then drops with the frequency of periodic potential.In the end of this part,results are revealed by analysing the concentration fields of T=0.06 s of square wave function.Finally,optimization of mixing efficiency is carried out based on the previous condition.On one hand,the initial phase of periodic potential is changed and it is concluded that the partial initial phase can improve the mixing efficiency and even make the mixture come to the perfect mixed state.On the other hand,installation position of the electrode and the applied position of the functional potential are changed to obtain four conditions,including the symmetry and asymmetry of the electrode as well as the same side and the opposite side position of the potential.In view of these four conditions,highest efficiency can be obtained under the conditions of T and it can also make the mixing preocess to a fully mixed state.