Non-contact manipulation of nonmagnetic materials by using a uniform magnetic field: Experiment and simulation

Magnetic field induced dynamic self-assembly (MFIDSA) can be regarded as one of non-contact manipulation method under special category of micro-scale or nano-scale fabrication technique, which is confined to magnetic materials. This study is focused on MFIDSA process of nonmagnetic materials in a magnetic multiphase fluid by using the experimental technique and numerical method. To explore the controllability of MFIDSA process, a series of experiments by using the magnetic multiphase fluid comprising of nonmagnetic polystyrene microparticles with different particle-size distributions were carried out. The relations of the strength of external magnetic field, the average length of self-assembled chain-like structures, and the particle-size distribution of nonmagnetic polystyrene microparticles were investigated experimentally. Meanwhile, to reveal the interaction mechanisms behind the self-assembling behaviours of nonmagnetic materials, an immersed boundary lattice Boltzmann method was applied to simulate the multi-physical field coupled multiphase flows in MFIDSA process. The present work shows that the average length of self-assembled chain-like structures is mainly determined by the strength of external magnetic field, irrespective of the particle-size distribution of nonmagnetic materials. The coincident results of the experiments and numerical simulations provide a guidance on how to manipulate the nonmagnetic materials to form the chain-like structures by magnetic field.