  In-line holographic video microscopy records a wealth of information about
the microscopic structure and dynamics of colloidal materials. Powerful
analytical techniques are available to retrieve that information when the
colloidal particles are well-separated. Large assemblies of close-packed
particles create holograms that are substantially more challenging to
interpret. We demonstrate that Rayleigh-Sommerfeld back-propagation is useful
for analyzing holograms of colloidomer chains, close-packed linear assemblies
of micrometer-scale emulsion droplets. Colloidomers are fully flexible chains
and undergo three-dimensional configurational changes under the combined
influence of random thermal forces and hydrodynamic forces. We demonstrate the
ability of holographic reconstruction to track these changes as colloidomers
sediment through water in a horizontal slit pore. Comparing holographically
measured configurational trajectories with predictions of hydrodynamic models
both validates the analytical technique for this valuable class of
self-organizing materials and also provides insights into the influence of
geometric confinement on colloidomer hydrodynamics.
