Driven colloidal suspensions in confinement and density functional theory: microstructure and wall-slip

Area of Science:

• Soft Matter Physics
• Colloidal Science
• Computational Physics

Background:

• Colloidal suspensions are complex fluids with unique properties under external forces.
• Understanding their behavior in confined geometries is crucial for material science and nanotechnology.
• Classical density functional theory provides a framework for studying such systems.

Purpose of the Study:

• To theoretically investigate the general properties of driven (sheared) colloidal suspensions in confinement.
• To develop and validate approximations for the one-particle density equation under shear.
• To analyze shear stress distribution and flow behavior near confining walls.

Main Methods:

• Application of classical density functional theory.
• Formulation of closure conditions for approximations to the Smoluchowski equation.
• Identification of the exact microscopic stress tensor.
• Development of a second equation to achieve homogeneous shear stress.

Main Results:

• A simple closure approximation was shown to fulfill general conditions for modeling sheared suspensions.
• The microscopic shear stress near a wall was found to be non-homogeneous.
• A homogeneous shear stress was achieved by introducing an additional equation.
• Local flow velocity and slip length at the wall were computed.

Conclusions:

• The developed theoretical framework accurately describes sheared colloidal suspensions in confinement.
• The findings provide insights into fluid dynamics at interfaces, relevant for complex fluid behavior.
• The computed slip length offers a quantitative measure of wall-fluid interaction in sheared systems.