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

Abstract

Magnetic polymer nanocomposites that can be tuned between steady and non-steady status were created based on the modification of Fe 3 O 4 nanoparticles via octadecylamine (ODA) and methoxypolyethylene glycols (MPEG) through covalent and ion bonding, respectively. The prepared Fe 3 O 4 @ODA was mixed with paraffine as two-components composites, and the synthesized Fe 3 O 4 @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.

Fabrication of a Dual Stimuli-Responsive Assorted Film Comprising Magnetic- and Gold-Nanoparticles with a Self-Assembly Protein of α-Synuclein

“…However, coassembly of NPs of different natures is challenging because their peculiar physical and chemical properties cause lack of effective chemical linkers commonly operative toward diverse NPs. Fabrication of NPs into a thin 2D array, in particular, would provide one of the most effective platforms to mediate external stimuli for precise control over the movement of soft actuators because NPs could be not only placed in uniform distribution over a large area to avoid irregular spatial response to a single stimulus but be also arranged in assorted or patterned arrays to respond to multiple stimuli, which is difficult to be accomplished via either simple blending of NPs with the soft matrix or functionalizing the polymer matrix itself. ,− Among various methods to produce the 2D array such as the Langmuir–Blodgett technique, , spin-coating process, , and evaporation technique, an approach of prefabricating NPs into free-standing 2D film has been pursued in this study because the resulting flexible films can be conformally transferred to soft bodies regardless of their surface shapes. In addition, fabrication of different types of NPs into a single assorted 2D film would produce multisensory system not only responding to simultaneously provided multiple stimuli but also improving their responsiveness toward the stimuli via possible synergistic effects between the NPs.…”