The Study Of Magnetically Induced Particle Deflection/concentration In Small Channels

Magnetic manipulation of particles/cells in magnetic fluids is a research field with a broad prospect.With the change of research methods in modern biology,the study of microfluidic chips for cells has attracted the attention of many researchers.At the same time,manipulation and sorting of cells/particles suspended in micro-channels can further solve many of the medical challenges faced.Generating external driving force,the magnetic field does not need to contact with particles/cells directly and works by generating magnetic force.This method is not only more efficient,but also in the whole experiment process won’t cause damage to the sample.The study of the migration/concentration of particles in the channel is crucial,which facilitates further manipulation and accurate analysis of the downstream channel.In view of the potential application of particle/cell magnetic manipulation in channels,this paper systematically calculated and experimentally studied the particle’s movement behavior under different magnetic fields.The purpose of this study is to explore the movement behavior of particles in channels under different magnetic field distribution and its influencing factors.Through theoretical and experimental comparisons,we find out the error cause and other potential influencing factors to improve the efficiency of particle magnetic manipulation.The particles used in experiment is not magnetic,and the liquid media is magnetic fluid,so it is not necessary to mark the particles.This paper theoretically calculates the trajectory of particles in the channel under different magnetic field distributions.The motion trajectory of the particle is mainly determined by forces applied by others.By analyzing,the particle is mainly affected by two forces during the movement,namely,magnetic force and stokes resistance.The magnetic force is mainly due to the difference in magnetic susceptibility between the particles and the media solution(magnetic fluid),and at the same time there is a magnetic field gradient in the channel due to the external magnetic field,which is a necessary condition for the magnetic force of the particles.In addition,the magnetic fluid is a liquid with a certain viscosity,and it will have some hindrance to the movement of the particles during the movement of the particles.Through force analysis of the particles,the motion equations of the particles are listed,and the motion trajectory curve of the particles is obtained.Based on the theoretical calculations and the numerical simulation method,the static magnetic equation and the fluid flow equation are solved by the numerical simulation method.The magnetic field and flow field distribution cloud diagram in the channel can be obtained,and the magnetic field and flow field distribution in different positions can be obtained more intuitively.During the experiment,we studied the influence of the distance between the magnet and the channel wall,the strength of the magnetic field,the size of the particles,and the concentration of the magnetic fluid on the trajectory of the particles under the monolithic,attracting,and repulsive magnetic field distributions.In the corresponding position,the bandwidth of the particles measured by the image superposition is compared with the theoretical calculation.Further analysis shows that the distance between the magnet and the channel wall,the strength of the magnetic field,the particle size,and the concentration of the magnetic fluid all have a great influence on the offset/aggregation of the particles.Meanwhile,the viscosity of the magnetic fluid and the release position of the particles also have effect on the movement trajectory of the particles to some extent.The viscosity of the magnetic fluid is negligible because of its small influence.While the release position of the particles cannot be accurately controlled during the experiment,its influence can be included in the scope of error analysis.Therefore,in the future particle/cell separation,capture and other experimental studies,in order to improve the efficiency of magnetic manipulation,we need to be further improved from these directions.This paper mainly studies three aspects,including theory,numerical simulation and experiment,hoping to provide theoretical and experimental basis for further research on particle/cell magnetic manipulation in the future.