The hydrodynamics of colloidal gelation

Area of Science:

• Colloid and Surface Science
• Soft Matter Physics
• Computational Materials Science

Background:

• Colloidal gels form via arrested phase separation, creating a network of attractive particles.
• Existing models often neglect hydrodynamic interactions, leading to mismatches with experimental observations.
• Understanding the role of these interactions is key to accurate gelation modeling.

Purpose of the Study:

• To investigate the impact of hydrodynamic interactions on colloidal gelation dynamics.
• To compare simulation results with and without hydrodynamic forces against experimental data.
• To elucidate the fundamental mechanisms governing arrested phase separation in colloidal systems.

Main Methods:

• Performed molecular dynamics simulations of colloidal gelation using HOOMD-blue.
• Executed simulations both with and without explicit inclusion of hydrodynamic interactions.
• Developed a simplified transport model to analyze competing processes near the gel boundary.

Main Results:

• Simulations including hydrodynamic interactions closely matched experimental observations.
• Neglecting hydrodynamic forces resulted in significant disparities, mirroring literature mismatches.
• Hydrodynamic interactions accelerate aggregate coagulation, shifting the gel boundary to lower attraction strengths and concentrations.

Conclusions:

• Hydrodynamic forces are essential for accurate colloidal gelation modeling.
• These forces significantly influence the competition between aggregate compaction and coagulation.
• A reevaluation of dynamic discrete element models for gelation kinetics is necessary to incorporate collective hydrodynamic effects.