Evaporation-induced
assembly of nanoparticles in a drying droplet
is of great importance in many engineering applications, including
printing, coating, and thin film processing. The investigation of
particle dynamics in evaporating droplets can provide fundamental
hydrodynamic insight for revealing the processing–structure
relationship in the particle self-organization induced by solvent
evaporation. We develop a free-energy-based multiphase lattice Boltzmann
method coupled with Brownian dynamics to simulate evaporating colloidal
droplets on solid substrates with specified wetting properties. The
influence of interface-bound nanoparticles on the surface tension
and evaporation of a flat liquid–vapor interface is first quantified.
The results indicate that the particles at the interface reduce surface
tension and enhance evaporation flux. For evaporating particle-covered
droplets on substrates with different wetting properties, we characterize
the increase of evaporate rate via measuring droplet volume. We find
that droplet evaporation is determined by the number density and circumferential
distribution of interfacial particles. We further correlate particle
dynamics and assembly to the evaporation-induced convection in the
bulk and on the surface of droplet. Finally, we observe distinct final
deposits from evaporating colloidal droplets with bulk-dispersed and
interface-bound particles. In addition, the deposit pattern is also
influenced by the equilibrium contact angle of droplet
