  We study the effect of a rough wall on the controllability of micro-swimmers
made of several balls linked by thin jacks: the so-called 3-sphere and 4-sphere
swimmers. We show that a controllable swimmer (the 4-sphere swimmer) is not
impacted by the roughness. On the contrary, we show that the roughness changes
the dynamics of the 3-sphere swimmer, so that it can reach any direction almost
everywhere.
