  We describe a microfluidic device for studying the orientational dynamics of
microrods. The device enables us to experimentally investigate the tumbling of
microrods immersed in the shear flow in a microfluidic channel with a depth of
400 mu and a width of 2.5 mm. The orientational dynamics was recorded using a
20 X microscopic objective and a CCD camera. The microrods were produced by
shearing microdroplets of photocurable epoxy resin. We show different examples
of empirically observed tumbling. On the one hand we find that short stretches
of the experimentally determined time series are well described by fits to
solutions of Jeffery's approximate equation of motion [Jeffery, Proc. R. Soc.
London. 102 (1922), 161-179]. On the other hand we find that the empirically
observed trajectories drift between different solutions of Jeffery's equation.
We discuss possible causes of this orbit drift.
