振荡复合梯度磁场作用下磁性微粒的解聚式分离特性研究

Magnetophoretic separation system based on the microfluidics has an extensive potential applications in biomedical and analytical chemistry. But in the existing technology system, the factors of single model of magnetic force and poor controllability make the aggregation of magnetic particles easy to occur, resulting in high-precision and high resolution separations can only exist in the case of lower particle concentration and limiting its further development and application. From the formation mechanism and influence factors of magnetic particle aggregation, this research proposes to inhibit the aggregation behavior of magnetic particles and realize the separation of disaggregating magnetic particles by changing the magnetic interation model of particles and regulating the particle distribution characteristics. Based on it, this research will optimize and design a gradient magnetic field with a combination of an uniform oscillating field in a pulsed way, whose magnetic field and gradient are decoupled; A microfluidic magnetophoretic separation platform for separating multi-diameter particles will be developed; The dynamics of magnetic force, motion, aggregation and disaggregating separation of particles under the action of a gradient magnetic field with a combination of an uniform oscillating field will be studied; And the interactions among the particle concentration, flow rate, field gradient, oscillating field strength and frequency under a high magnetic separation efficiency will be discussed. All these will provide the theoretic foundation and experimental evidence for establishing and improving an efficient magnetophoretic separation system.

基于微流控芯片技术的磁泳分离系统在生物医学和分析化学等领域具有广阔的应用前景。但在现有的技术体系中，磁场力作用模式单一和可控性差等因素使得磁性微粒间易发生磁团聚行为，导致系统只能在较低微粒浓度下实现高精度和高分辨率分离，限制了其进一步发展和应用。本项目从梯度磁场下磁团聚形成机理和影响因素出发，提出通过转变磁性微粒间磁作用力模式和调节梯度磁场力分布特性来抑制磁团聚行为和实现微粒的解聚式分离。基于此，拟优化设计磁场强度和梯度可解耦控制的脉冲式振荡复合梯度磁场系统，研制多粒径磁性微粒的微流控磁泳分离实验平台，研究振荡复合梯度磁场和流场作用下微管道中磁性微粒的受力、运动、团聚和解聚式分离等动力学特性，探讨高分离效率下微粒浓度、流速、磁场梯度、振荡磁场强度及频率间的作用关系，为建立和完善高效磁泳分离系统提供理论基础和实验依据。

针对现有磁泳系统中磁性微粒的团聚行为使得多目标微粒无法通过自身物理参量差异而实现高效分离这一难题，本项目以微流控环境下的微米级磁性颗粒为研究对象，从微粒发生磁团聚的作用机理出发，提出采用振荡复合梯度磁场来改变磁性微粒间的磁作用力模式，通过将传统静态系统下的单一吸力变为交替的吸-斥力状态来抑制磁性微粒的团聚行为，进而实现磁性微粒的动态解聚式分离。所取得的主要成果有：（1）基于任意拉格朗日-欧拉法和应力张量法建立了均匀/梯度磁场和流场作用下磁性微粒动力学行为的直接数值模型，解决了传统磁偶极子模型计算精度差、单向耦合等问题，实现了微粒与微粒、微粒与流体间的强耦合求解，为探究磁性微粒的团聚、解聚及分离行为提供了重要的分析途径。（2）构建了一套由集成内部微电磁体和外部永磁体组成的混合磁体系统，实现了磁场强度-梯度的有效解耦和磁场力大小及方向的调控，在此基础上构建了相应的实验平台，验证了方案的有效性，为调控磁性微粒的动力学行为提供了重要的技术手段。（3）提出了一种可产生磁场方向水平-垂直交替变化但梯度磁场力方向不变的振荡复合梯度磁场系统，在此基础上探究了磁性微粒在该类磁场作用下的受力特性和动力学行为，验证了其用于实现磁性微粒解聚分离的有效性，并揭示了振荡式磁相互作用力和定向梯度磁场力对解聚分离效率的作用机制，为实现多目标磁性微粒高效分离提供了重要的理论支撑。