Study On The Magnetic Assembly Of Magnetic Particles And Its Influence On The Distribution Characteristics Of Particle Settlement

Magnetic targeting is a kind of magnetic manipulation technology that uses gradient magnetic fields to transport magnetic micro-and nano-particles to the target area,which has attracted widespread attention due to its potential applications in various fields from macro-to micro-scale,(such as magnetic gene and drug delivery,magnetic separation and magnetic trapping).At present,in the existing magnetic targeting theory,technology and application research,static magnetic field is still the most frequently used magnetic field type.When exploring the mechanism of particle motion,the effect of the magnetic gradient force produced by the external non-uniform magnetic field is mainly considered,and the magnetic inter-particle force and its effect on the final distribution of particles in the target area are ignored.However,in many applications,the distribution characteristics of magnetic particles and assembles in the target area are crucial.For example,in magnetofection,the distribution of magnetic gene carriers directly determines the efficiency of their contact with cells in the target area,which in turn affects the transfection efficiency.In order to investigate the magnetic assembly behavior induced by magnetic inter-particle force and its influence on the particle's distribution characteristics of the target area,this study combined simulations and experiments to explore the magnetic assembly behavior and its influence on particle distribution.The relevant research results have great value for understanding and optimizing magnetic targeting behavior and magnetic field system design in theory and applications.At the theory and simulation levels,the three-dimensional Monte Carlo and analytical simulation models of the magnetic particle sedimentation system were established,which provided effective methods for simulating the particle assembly and sedimentation characteristics under static and dynamic magnetic fields.At the same time,the parameters such as the coverage ratio,average distance and chain length distribution of the particles in the target area are defined,which provides the possibility to qualitatively describe the final distribution pattern of the particles.At the experimental device level,a new dual-coil magnetic field source system with orthogonal axes is designed and developed,which provides conditions for generating the static magnetic field,biaxial alternating magnetic field and step-type dynamic magnetic field required for the experiments.Based on the above research conditions,this paper explores the effect of the magnetic inter-particle force on the particle movement behavior under the traditional static magnetic field,and the modulation effect of two types of dynamic magnetic fields on the movement and distribution of particles in the target area.The simulation and experimental results show that the magnetic inter-particle force has a significant effect on the motion behavior of particles and the final distribution characteristics in the target area.Among them,under the static vertical magnetic field,the particles assemble along the direction perpendicular to the bottom surface of the container(target area),which makes it difficult for some particles to settle down and results in lower coverage ratio compared with the case without the magnetic interaction force,and under static horizontal magnetic field,particles distribute unevenly after settling down due to assembling along the horizontal direction.For the dynamic magnetic field,the study found that the final distribution pattern parameters of the particles at the bottom of the micro-container can be adjusted by applying a biaxial alternating magnetic field during the sedimentation process,including the average particle coverage and separation distance.However,the particle distribution becomes worse compared to the case under vertical static magnetic field.Further research has found that step-type dynamic magnetic field can improve this problem,which can increase the average ratio while ensuring that the distribution of particles remains even.