6 research outputs found
Dynamics of individual Brownian rods in a microchannel flow
We study the orientational dynamics of heavy silica microrods flowing through
a microfluidic channel. Comparing experiments and Brownian dynamics simulations
we identify different particle orbits, in particular in-plane tumbling
behavior, which cannot be explained by classical Jeffery theory, and we relate
this behavior to the rotational diffusion of the rods. By constructing the
full, three-dimensional, orientation distribution, we describe the rod
trajectories and quantify the persistence of Jeffery orbits using temporal
correlation functions of the Jeffery constant. We find that our colloidal rods
lose memory of their initial configuration in about a second, corresponding to
half a Jeffery period.Comment: 5 pages, 4 figure
Capillary nematisation of colloidal rods in confinement
We confine a colloidal liquid crystal between parallel plates separated down to several times the rod length. By connecting the system to a reservoir we effectively create a grand canonical system, in which the liquid crystal displays an isotropic phase in the reservoir, but upon strong confinement becomes nematic between the parallel plates. This capillary nematisation transition can be followed down to the single particle level by means of laser scanning confocal microscopy. We compare the experimental findings to density functional theories (DFTs), within the Zwanzig model as well as a more advanced DFT, in which the effect of rod flexibility is taken into account
Particle Shape Anisotropy in Pickering Emulsions: Cubes and Peanuts
We have investigated the effect of
particle shape in Pickering
emulsions by employing, for the first time, cubic and peanut-shaped
particles. The interfacial packing and orientation of anisotropic
microparticles are revealed at the single-particle level by direct
microscopy observations. The uniform anisotropic hematite microparticles
adsorb irreversibly at the oil–water interface in monolayers
and form solid-stabilized o/w emulsions via the process of limited
coalescence. Emulsions were stable against further coalescence for
at least 1 year. We found that cubes assembled at the interface in
monolayers with a packing intermediate between hexagonal and cubic
and average packing densities of up to 90%. Local domains displayed
densities even higher than theoretically achievable for spheres. Cubes
exclusively orient parallel with one of their flat sides at the oil–water
interface, whereas peanuts preferentially attach parallel with their
long side. Those peanut-shaped microparticles assemble in locally
ordered, interfacial particle stacks that may interlock. Indications
for long-range capillary interactions were not found, and we hypothesize
that this is related to the observed stable orientations of cubes
and peanuts that marginalize deformations of the interface