Field-Induced Structure of Confined Ferrofluid Emulsion

Lawrence, Eric M.; Ivey, Mark L.; Flores, G. A.; Liu, Jing; Bibette, Jérôme; Richard, J.

doi:10.1142/s0217979294001111

Cited by 21 publications

(13 citation statements)

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“…Labyrinthine structures similar to sheets have been observed in ferrofluids, but the structure within the sheets was not ascertained [21]. The presence of hexagonal sheets has not been reported in previous experimental observations on ER fluids, but has been observed in simulations [11,12,[22][23][24].…”

Section: Discussionmentioning

confidence: 86%

Structure of electrorheological fluids

Dassanayake

Fraden

Blaaderen

2000

The Journal of Chemical Physics

175

178

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Specially synthesized silica colloidal spheres with fluorescent cores were used as model electrorheological fluids to experimentally explore structure formation and evolution under conditions of no shear. Using Confocal Scanning Laser Microscopy we measured the location of each colloid in three dimensions. We observed an equilibrium body-centered tetragonal phase and several non-equilibrium structures such as sheet-like labyrinths and isolated chains of colloids. The formation of non-equilibrium structures was studied as a function of the volume fraction, electric field strength and starting configuration of the colloid. We compare our observations to previous experiments, simulations and calculations.

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Section: Discussionmentioning

confidence: 86%

Structure of electrorheological fluids

Dassanayake

Fraden

Blaaderen

2000

The Journal of Chemical Physics

175

178

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“…In each case, we injected the same initial concentration of beads, but washed the beads with a different surfactant. In previous studies [24] on the self-assembly of magnetic bead columns, it appeared that the center-to-center spacing between the columns only depended on the channel height and the rate that the magnetic field was applied. Qualitatively, increasing the height of the channel increases the length of a column and its corresponding magnetic dipole, which in turn increases the repulsion between nearby columns.…”

Section: Continuous-time Random Walk Interpretation Of the Experimentmentioning

confidence: 99%

Motion of single long DNA molecules through arrays of magnetic columns

et al. 2005

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We present a videomicroscopy study of T4 DNA (169 kbp) in microfluidic arrays of posts formed by the self-assembly of magnetic beads. We observe DNA moving through an area of 10 000 microm(2), typically containing 100-600 posts. We determine the distribution of the contact times with the posts and the distribution of passage times across the field of view for hundreds of DNA per experiment. The contact time is well approximated by a Poisson process, scaling like the inverse of the field strength, independent of the density of the array. The distribution of passage times allows us to estimate the mean velocity and dispersivity of the DNA during its motion over distances long compared to our field of view. We compare these values with those computed from a lattice Monte Carlo model and geometration theory. We find reasonable quantitative agreement between the lattice Monte Carlo model and experiment, with the error increasing with increasing post density. The deviation between theory and experiment is attributed to the high mobility of DNA after disengaging from the posts, which leads to a difference between the contact time and the total time lost by colliding. Classical geometration theory furnishes surprisingly good agreement for the dispersivity, while geometration theory with a mean free path significantly overestimates the dispersivity.

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“…When viewed from the top, the columns can be modeled by a 2D plane containing purely repulsive dipoles. This model fails to capture the effects of chain coalescence that occur in a truly 3D system [21], but it serves as a starting point for understanding the intercolumn structure in the channel system.…”

Section: Simulation Detailsmentioning

confidence: 99%

Structural analysis of a dipole system in two-dimensional channels

Haghgooie

Doyle

2004

Phys. Rev. E

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A system of magnetic dipoles in two-dimensional (2D) channels was studied using Brownian dynamics simulations. The dipoles interact with a purely repulsive r(-3) potential and are confined by two hard walls in one of the dimensions. Solid crystals were annealed in the 2D channels and the structural properties of the crystals were investigated. The long-ranged nature of the purely repulsive dipoles combined with the presence of hard walls led to structural deviations from the unbounded (infinite) 2D dipolar crystal. The structures in the channels were characterized by a high density of particles along the walls. The particles along the wall became increasingly localized as the channel width was increased. The spacing of the walls was important in determining the properties of the structures formed in the channel. Small changes in the width of the channel induced significant structural changes in the crystal. These structural changes were manifested in the density profiles, defect concentrations, and local bond-orientation order of the system. Oscillations in the structural properties were observed as the channel width was increased, indicating the existence of magic-number channel widths for this system. As the channel width was increased the properties of the confined system approached those of the unbounded system surprisingly slowly.

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Field-Induced Structure of Confined Ferrofluid Emulsion

Cited by 21 publications

References 0 publications

Structure of electrorheological fluids

Structure of electrorheological fluids

Motion of single long DNA molecules through arrays of magnetic columns

Structural analysis of a dipole system in two-dimensional channels

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