Directed flow and assembly of magnetic polymer nanocomposites switchable between steady and non-steady status driven by magnetic field

Magnetic polymer nanocomposites that can be tuned between steady and non-steady status were created based on the modification of Fe₃O₄ nanoparticles via octadecylamine (ODA) and methoxypolyethylene glycols (MPEG) through covalent and ion bonding, respectively. The prepared Fe₃O₄@ODA was mixed with paraffine as two-components composites, and the synthesized Fe₃O₄@MPEG was used as one-component composites. These nanocomposites can flow or be assembled driven by moving or static magnetic fields at a temperature higher than the melting temperature. Fluids in channels or pipelines can be controlled by the directed flow and subsequent fixation, while the directed assembly can be used to create arbitrary surface patterns that can be easily erased upon heating without magnetic field. Besides, the damages on the surface patterns can be healed upon heating in the presence of magnetic field. Simulation was used to understand the dominant factors on surface topography. During directed assembly, the surface topography is dominated by the pattern geometry. The topography of the nanocomposites during flow is controlled mainly by the moving velocity. This work provides candidate smart polymer nanocomposites for magnetic-induced construction of surface patterns and control of liquid transportation in channels and pipelines.