Mesoscale Simulation of Structure Formation and Rheology on Colloidal Nanoparticles

Abstract

A mesoscale simulation of concentrated colloidal nanoparticles in a simple shear between parallel flat plates is carried out to investigate structure formation of the nanoparticles and rheology of the colloid. The motion of nanoparticles is calculated by an off-lattice Newtonian dynamics, and the flow of solvent is calculated by an on-lattice fluctuating Navier-Stokes equation. A fictitious domain method is used to couple the motion of nanoparticles with the flow of solvent. The present simulation counts all crucial interactions, such as contact force and torque, van der Waals force, electrostatic force, hydrodynamic force and torque including thermal fluctuation of the solvent that causes translational and rotational Brownian motions of the nanoparticles. Three-dimensional simulations at Peclet number of 100 and 1000 are performed. The results show that the aggregation of nanoparticles takes place as a function of Peclet number. The aggregated structure of nanoparticles changes considerably the velocity profile between the flat plates to a sigmoid curve, so that the apparent viscosity of colloid increases. The increment of apparent viscosity depends on the size of aggregated structure of nanoparticles.