Directed self-assembly of field-responsive fluids in confined geometries†

We present an investigation into the important physical principles associated with the self-assembly of magnetorheological (MR) fluids in the microfluidic setting. We concentrate on the role of channel topology in influencing the resulting microstructure. In particular, using Brownian dynamics simulations, we show how a variety of geometrically-simple confining microchannels can be used to strongly control the lattice type and orientation in self-assembled MR fluids. Additionally, we demonstrate how topographical features can be used to dictate the order (or disorder) of the steadystate structure. We highlight the similarities and differences between our three-dimensional microchannel system and the structures and dynamics observed in two-dimensional confined systems. Furthermore, we present an example of the introduction of local magnetic field inhomogeneity and its strong influence over the resulting self-assembled MR fluid structure.