  Achieving control over the directionality of active colloids is essential for
their use in practical applications such as cargo carriers in microfluidic
devices. So far, guidance of spherical Janus colloids was mainly realized using
specially engineered magnetic multilayer coatings combined with external
magnetic fields. Here, we demonstrate that step-like sub-micron topographical
features can be used as reliable docking and guiding devices for chemically
active spherical Janus colloids. For various topographic features (stripes,
squares or circular posts) docking of the colloid at the feature edge is robust
and reliable. Furthermore, the colloids move along the edges for significantly
long times, which systematically increase with fuel concentration. The observed
phenomenology is qualitatively captured by a simple continuum model of
self-diffusiophoresis near confining boundaries, indicating that the chemical
activity and associated hydrodynamic interactions with the nearby topography
are the main physical ingredients behind the observed behaviour.
