  Shapes of colloids matter at liquid interfaces. We explore the interactions
between rough-surfaced nanocolloids at the air--water interface through the
compaction of monolayers experimentally and numerically. Sufficiently rough
systems exhibit a non-trivial intermediate state between a gas-like state and a
close-packed jamming state due to roughness-induced capillary attraction. We
also find that roughness-induced friction lowers the jamming point, and the
tangential contact force owing to surface asperities can cause a gradual
off-plane collapse of the compressed monolayer.
