Mesoscale Simulation of Nanoparticle Deposition in Evaporating Colloidal Droplet

The research on nanoparticle deposition induced by evaporation of colloidal droplet expands rapidly in the past years due to its importance in many applications, including materials printing and thin-film processing. Revealing the detailed particle dynamics during evaporation can produce understanding of the much-needed processing-structure relationships in the drying process. We apply a 3D lattice Boltzmann-Brownian dynamics model to simulate evaporating sessile droplets with particles dispersed in the bulk and adsorbed at the interface. A new LBM fluid model is developed to model liquid-vapor phase change heat transfer of a single-component fluid with a contact line pinning scheme that allows us to explore evaporation on solid substrates with different wetting properties, namely constant contact radius and constant contact angle regimes. We observe the process of nanoparticle self-assembly during the evaporation of droplets and quantitatively analyze the deposit structure. We further elucidate the particle dynamics in the presence of Marangoni convection induced by inhomogeneous evaporation, which provide critical insight into evaporation-driven depositions under experimentally relevant conditions.