Experimental Research Of Cell Separation Based On Hydrodynamic Force

Microfluidics has been attracting significant attention for the past two decades due to its high efficiency,accuracy and low cost in biological and medical applications.Needs of high efficiency and low consumption in the clinical care are increasingly urgent.Meanwhile,separating target particles from the mixture is one of the classical research fields in these microfluidic applications.So separating desired cells by using microfluidic chips meets requirements of medical treatment about efficiency and cost,which has a great clinical significance.This thesis presents a new approach for cell separation based on hydrodynamic force by using microfluidic chips as a platform.The asymmetric focusing of sample flow is formed by the induced sheath flows with different viscosity on the sides of sample flow.Meanwhile,the accelerated motion and the velocity profile of high-velocity gradient in the sample flow is obtained.The hydrodynamic force(Saffman lift force)induced by the highvelocity gradient is exerted on particles,which plays a dominate role in the particle deflection due to the high-velocity gradient.The larger particles will deflect away from their original streamline to the high relative velocity side,while the smaller particles remain close to their streamline or experience a smaller deflection than the larger particles.Through different deflection,the different size particles can be separated.In order to obtain accurate experimental result,two kinds of polystyrene microspheres with diameters 1.0 ?m(red fluorescent)and 9.9 ?m(green fluorescent)are adopted as the sample to verify the principle and quantify the difference of variables in experiments of this thesis.In final chapter,blood cells and Escherichia coli are used as the sample to verify the feasibility of this new approach in the biological application.Through a series of validation experiments,the analysis about the principle of this new particle separation approach is verified.The results of quantitative experiments indicated increasing of the flow rate of low-viscosity sheath flow and viscosity difference between high-viscosity and low-viscosity sheath flows improves separation effect.While increasing of keeping flow rate ratio among sample flow and sheath flows and flow rate of highviscosity sheath flow weaken separation effect.At last,separation and enrichment of different size particles and separation between blood cells and Escherichia coli are successfully achieved by using this new approach.