Poisson-Nernst-Planck Model For Numerical Simulation Of Electroosmotic Flow In Microchannels

Microfluidic chips centralize the pretreatment, chemical reaction, separation and detection of sample and transfers to a few square centimeters of chip.The core problem of microfluidic chips with characteristics of micromation, integration, automation and simplicity is the drive and control of microfluid.This paper had studied the characteristics of electroosmotic flow(EOF) in 2D microchannels through the analysis of basic theoretical,the research of numerical simulation by Poisson-Nernst-Planck model and experiment.The main research achievements and innovations of this paper as follows:Firstly,this paper had a deep understanding of microfluidic system of electric phenomenon and the formation mechanism of EOF,and studied the multi-physical features of Poisson-Boltzmann(PB) and Poisson-Nernst-Planck(PNP) model through deep understanding of double electrode layer(EDL) model. Based on control equations of physical field to establish PNP coupling model which were the theoretical basis for EOF numerical simulation researchs.Secondly,based on the same physical conditions and geometric model to predict the EOF in microchannel by PNP and PB model.Through compared and analysed the electric potential distributions and velocity distributions between the PB and PNP model to infer that the ions distribution of low-concentration solution in EDL was't completely obey Boltzmann distribution,and PNP model can more accurately predict the ions distribution in EDL than PB model. So verified the PNP model was more universal than PB model.Thirdly,this paper had adopted current monitoring method to realize the real-time monitoring of the velocity of EOF in PMMA chip. Through compared and analysed the experimental data and simulated data to find velocity variations with the solution concentration and electric intensity by experiment and PNP model for Numerical Simulation were the same,so verified the the accuracy of the PNP models.Fourthly,this paper had studied the characteristics of EOF in entrance area of 2D microchannel,ion concentration distribution characteristics in different concentration solution,and the influences of solution concentration,the height of microchannel and electric intensity on the EOF velocity in steady state throuth numerical simulation by PNP model. Solution concentration and EOF velocity were nonlinear related,high-concentration solution had slower EOF velocity.The height of microchannel barely affected EOF velocity.EOF velocity linear growed with electric intensity increased.Through the controlling of olution concentration and applied electric intensity.Finaly,throuth numerical simulation by PNP model to study the characteristics of EOF in 2D microchannel with non-uniform zeta potential distribution on two walls, step change in zeta potential distribution and zeta potential complicated distribution along flow direction.lt had found there was flow circulation in step change in plus-minus zeta potential distribution and step change and linear change with discontinuous zeta in chang point alternate distribution along flow direction.Flow circulation in the latter was stronger than in the former.It can infer that step change and linear change with discontinuous zeta in chang point alternate distribution along flow direction could enhance the micromixing effectively.Through microchannels surface modification processing method to change zeta potential distribution of channels surface can enhance micromixing in practical applications.