  The issue of the stability of Pickering emulsions is tackled at a mesoscopic
level using dissipative particle dynamics simulations within the Adiabatic
Biased Molecular Dynamics framework. We consider the early stage of the
coalescence process between two spherical water droplets in decane solvent. The
droplets are stabilized by Janus nanoparticles of different shapes (spherical
and ellipsoidal) with different three-phase contact angles. Given a
sufficiently dense layer of particles on the droplets, we show that the
stabilization mechanism strongly depends on the collision speed. This is
consistent with a coalescence mechanism governed by the rheology of the
interfacial region. When the system is forced to coalesce sufficiently slowly,
we investigate at a mesoscopic level how the ability of the nanoparticles to
stabilize Pickering emulsions is discriminated by nanoparticle mobility and the
associated caging effect. These properties are both related to the
interparticle interaction and the hydrodynamic resistance in the liquid film
between the approaching interfaces.
