균일한 외부자기장 하에서의 원형 야누스 자기입자의 거동

다국어 초록 (Multilingual Abstract)

We numerically investigated the dynamics of circular Janus magnetic particles suspended in a viscous liquid, exposed to a uniform magnetic field applied externally. Each Janus particle has both magnetic part and non-magnetic one in a single particle. A direct simulation method, based on the Maxwell stress tensor and a fictitious domain method, is employed to solve the problem. Since we are concerned with a microfluidic application, we neglect inertia of particles and fluid. The previous numerical scheme for isotropic magnetic particles is improved further, enabling us to take into account the anisotropy of magnetic property. First, we validate the numerical scheme. Next, the dynamics of a single particle in the uniform field is investigated to see the effect of the material orientation on the rotational motion. The orientation of a single particle is aligned with the field direction due to the magnetic torque created by magnetic anisotropy. Then, we extended our interest to a two-particle problem. Depending on the initial angle between the field and the line-of-centers between the two particles, two distinct behaviors in particle path are observed. The detailed particle motions and the final conformations are also influenced by the intial orientations of the particles. As reported in several experimental studies on Janus particles, there exist two types of particle alignment: the straight configuration and the staggered one. We also discussed the difference in particle dynamics between Janus and isotropic particles.