We perform electrostatic many-body dissipative particle dynamics (MDPD) simulations to study the self-assembly and deposition of Janus particles in a drying thin film. A finite-difference Poisson solver is applied to calculate the important long-range electrostatic interactions in the system, taking account for the dielectric variations across the moving liquid-vapor interface under evaporation. Due to the unique anisotropy of Janus particles, their orientations in the final deposits is a key factor influencing the physico-chemical properties of dried colloidal suprastructures. We probe the fast rotation dynamics of Janus particles during the evaporation process to elucidate the interplay between the electrostatic interactions with substrate, image force due to dielectric discontinuity, and inter-particle electrostatic repulsions and hydrophobic interactions. The different dynamics of particles before and after breaching the liquid-vapor interface is analyzed with special attention. The effect of substrate charge, evaporation rate, and particle Janus balance on the deposit structure and particle orientations are studied to further the understanding of critical processing-structure relationship for using Janus particles as coating materials.

Modeling evaporation-driven deposition of Janus particles

256th National Meeting (2018)

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