  In inertial microfluidics lift forces cause a particle to migrate across
streamlines to specific positions in the cross section of a microchannel. We
control the rotational motion of a particle and demonstrate that this allows to
manipulate the lift-force profile and thereby the particle's equilibrium
positions. We perform two-dimensional simulation studies using the method of
multi-particle collision dynamics. Particles with unconstrained rotational
motion occupy stable equilibrium positions in both halfs of the channel while
the center is unstable. When an external torque is applied to the particle, two
equilibrium positions annihilate by passing a saddle-node bifurcation and only
one stable fixpoint remains so that all particles move to one side of the
channel. In contrast, non-rotating particles accumulate in the center and are
pushed into one half of the channel when the angular velocity is fixed to a
non-zero value.
