Colloidal particle adsorption at liquid interfaces: capillary driven dynamics and thermally activated kinetics

Area of Science:

• Colloid and interface science
• Soft matter physics
• Statistical mechanics

Background:

• Colloidal microparticle adsorption at water-oil interfaces exhibits slow relaxation to equilibrium.
• This slow kinetics is attributed to nanoscale surface defects creating metastable contact line configurations.
• Previous models focused on relaxation kinetics, leaving initial adsorption dynamics unstudied.

Purpose of the Study:

• To develop a comprehensive model describing the entire adsorption process of single colloidal particles at liquid interfaces.
• To account for metastable states induced by surface defects and thermal fluctuations.
• To accurately predict the crossover from fast capillary-driven to slow thermally activated kinetics.

Main Methods:

• Development of a Langevin model incorporating metastable states and thermal motion.
• Inclusion of a drag term based on the fluctuation-dissipation theorem to account for interface fluctuations.
• Langevin dynamics simulations to model the adsorption process.

Main Results:

• The proposed Langevin model successfully describes the complete adsorption dynamics.
• The model captures the crossover from fast initial adsorption to slow logarithmic relaxation.
• Simulations show close agreement with experimental observations for various microparticles.

Conclusions:

• The Langevin model provides a unified framework for understanding colloidal particle adsorption kinetics.
• Surface defects and thermal fluctuations are crucial for explaining the observed adsorption dynamics.
• The model accurately predicts the transition to slow, thermally activated kinetics.