  The displacement of a suspension of particles by an immiscible fluid in a
capillary tube or in a porous media is a canonical configuration that finds
application in a large number of natural and industrial applications, including
water purification, dispersion of colloids and microplastics, coating and
functionalization of tubings. The influence of particles dispersed in the fluid
on the interfacial dynamics and on the properties of the liquid film left
behind remain poorly understood. Here, we study the deposition of a coating
film on the walls of a capillary tube induced by the translation of a
suspension plug pushed by air. We identify the different deposition regimes as
a function of the translation speed of the plug, the particle size, and the
volume fraction of the suspension. The thickness of the coating film is
characterized, and we show that similarly to dip coating, three coating
regimes, liquid only, heterogeneous, and thick films, are observed. We also
show that, at first order, the thickness of films thicker than the particle
diameter can be predicted using the effective viscosity of the suspension.
Nevertheless, we also report that for large particles and concentrated
suspensions, a shear-induced migration mechanism leads to local variations in
volume fraction and modifies the deposited film thickness and composition.
