Harnessing Complex Fluid Interfaces to Control Colloidal Assembly and Deposition

Using lattice Boltzmann-Brownian dynamics (LB-BD) simulations, we model large-scale assembly of nanoparticles on liquid-vapor interfaces with complex geometries and investigate subsequent deposition upon complete evaporation. Particles aggregate into hexagonally close-packed monolayers on flat and spherical interfaces given appropriate value of the interaction parameter that couples fluid hydrodynamics and discrete particle dynamics. Detailed force analysis reveals a long-range attraction between particles, mimicking capillary interactions due to interface disturbance. On curved fluid interfaces with complex curvature fields, the particle dynamics is governed by pair capillary interactions and curvature-induced capillary migration. We develop a minimal theoretical model to predict equilibrium particle distribution on non-evaporating curved interfaces, which agrees well with simulation observation. Finally, we demonstrate that the interplay between evaporation-induced convective flow, particle pair interaction, and curvature-particle interaction results in distinct deposition patterns, which were obtained by using curved fluid interfaces as templates.