  When a drop containing colloidal particles evaporates on a surface, a
circular stain made of these particles is often observed due to an internal
flow toward the contact line. To hinder this effect, several approaches have
been proposed such as flow modification by addition of surfactants or control
of the interactions between the particles. All of these strategies involve the
liquid phase while maintaining the drying process. However, substitution of
evaporation by absorption into the substrate of the solvent has been
investigated less. Here, we show that a droplet containing colloidal particles
deposited on swelling hydrogels can lead to a nearly uniform coating. We report
experiments and theory to explore the relation between the gel swelling,
uniformity of deposition and the adsorption dynamics of the particles at the
substrate. Our findings suggest that draining the solvent by absorption
provides a robust route to homogeneous coatings.
