  We study the behavior of self-propelled nano- and micro-rods in three
dimensions, confined between two parallel walls, by simulations and scaling
arguments. Our simulations include thermal fluctuations and hydrodynamic
interactions, which are both relevant for the dynamical behavior at nano- to
micrometer length scales. In order to investigate the importance hydrodynamic
interactions, we also perform Brownian-dynamics-like simulations. In both
cases, we find that self-propelled rods display a strong surface excess in
confined geometries. An analogy with semi-flexible polymers is employed to
derive scaling laws for the dependence on the wall distance, the rod length,
and the propulsive force. The simulation data confirm the scaling predictions.
