Ion Concentration Polarization In U-shaped Micro-nanochannel System And Its Application Simulation Research

With the wide application of micro-nano system in electroosmotic micro-pump,desalination,molecular enrichment and other engineering fields,more and more people pay attention to the theoretical research of micro-nano system.U-shaped micro-nanochannel,as a basic micro-nanochannel structure,can produce obvious flow disturbance and can be used as a microfluidic mixer,electroosmotic micro-pump or even a cell lysis device.However,the theoretical research on U-shaped micro-nanochannel is still in the initial stage.In this paper,the electrokinetic characteristics of U-shaped micro-nanochannel system are studied by means of numerical simulation,and the influences of key physical parameters(external voltage,external pressure)and structural parameters(number of nanochannels,spacing of nanochannels)on system output indexes(electric field,pressure,shear stress,etc.)are analyzed.Simulation results show that ion concentration polarization is caused by ion selective transport in the nanochannels,and significantly enhanced electric field and electrokinetic flow are generated in the ion depletion region at the micro-nano junction.The current intensity,fluid velocity and maximum shear stress increase linearly with the increase of external voltage.Simulation of systems with different number of nanochannels and nanochannel spacing shows that increasing the number of nanochannels and increasing the distance between nanochannels can enhance the pressure difference at the micro-nano junction,and only by increasing the number of nanochannels can enhance the electric field at the micro-nano junction.Increasing the pressure flow will cause the ion depletion area to be compressed until it is completely destroyed,thus reducing the desalination effect of the system and making it lose locally enhanced shear flow.The electrokinetic characteristics of U-shaped micro-nanochannel system revealed in this paper have guiding significance for the application of seawater desalination,electroosmotic micro-pump and other related fields.