  An important challenge in active matter lies in harnessing useful global work
from entities that produce work locally, e.g., via self-propulsion. We
investigate here the active matter version of a classical capillary rise
effect, by considering a non-phase separated sediment of self-propelled Janus
colloids in contact with a vertical wall. We provide experimental evidence of
an unexpected and dynamic adsorption layer at the wall. Additionally, we
develop a complementary numerical model that recapitulates the experimental
observations. We show that an adhesive and aligning wall enhances the
pre-existing polarity heterogeneity within the bulk, enabling polar active
particles to climb up a wall against gravity, effectively powering a global
flux. Such steady-state flux has no equivalent in a passive wetting layer.
