  Polymer brushes are increasingly used to tailor surface physicochemistry for
various applications such as wetting, adhesion of biological objects,
implantable devices, etc. We perform Dissipative Particle Dynamics simulations
to study the behavior of dense polymer brushes under flow in a slit-pore
channel. We discover that the system displays flow inversion at the brush
interface for several disconnected ranges of the imposed flow. We associate
such phenomenon to collective polymer dynamics: a wave propagating on the brush
surface. The relation between the wavelength, the amplitude and the propagation
speed of the flow-generated wave is consistent with the solution of the Stokes
equations when an imposed traveling wave is assumed as boundary condition (the
famous Taylor's swimmer).
