  Magnetic skyrmions, topologically stabilized chiral magnetic textures with
particle-like properties have so far primarily been studied statically. Here,
we experimentally investigate the dynamics of skyrmion ensembles in metallic
thin film conduits where they behave as quasi-particle fluids. By exploiting
our access to the full trajectories of all fluid particles by means of
time-resolved magneto-optical Kerr microscopy, we demonstrate that boundary
conditions of skyrmion fluids can be tuned by modulation of the channel
geometry. We observe as a function of channel width deviations from classical
flow profiles even into the no- or partial-slip regime. Unlike conventional
colloids, the skyrmion Hall effect can also introduce transversal
flow-asymmetries and even local motion of single skyrmions against the driving
force which we explore with particle-based simulations, demonstrating the
unique properties of skyrmion liquid flow that uniquely deviates from
previously known behavior of other quasi-particles.
