  Motility-induced wall aggregation of active Brownian particles (ABPs) is a
well-studied phenomenon. Here, we study the aggregation of ABPs on porous
walls, which allows the particles to penetrate through at large motility. We
show that the active aggregates undergo a morphological transition from a
connected dense-phase to disconnected droplets with an increase in wall
porosity and the particle self-motility, similar to wetting-dewetting
transitions in equilibrium fluids. We show that both morphologically distinct
states are stable, and independent of initial conditions at least in some
parameter regions. Our analysis reveals that changes in wall porosity affect
the intrinsic properties of the aggregates and changes the effective
wall-aggregate interfacial tension, consistent with the appearance of the
morphological transition. Accordingly, a close analysis of the density, as well
as orientational distribution, indicates that the underlying reason for such
morphological transitions is not necessarily specific to the systems with
porous walls, and it can be possible to observe in a larger class of confined,
active systems by tuning the properties of confining walls.
