Aggregation of discoidal particles due to depletion interaction

Area of Science:

• Colloid and Surface Science
• Soft Matter Physics
• Biophysics

Background:

• Depletion interactions between larger particles in a solution of smaller particles can drive self-assembly.
• This phenomenon is crucial in colloidal systems, notably in the aggregation of red blood cells (erythrocytes), which impacts blood rheology.
• Understanding these interactions is key to controlling material properties and biological functions.

Purpose of the Study:

• To investigate the equilibrium state of discoidal colloids interacting via depletion with smaller depletant particles.
• To develop and validate a thermodynamic model for depletion-induced aggregation.
• To explore the influence of attractive interactions between depletant and discoidal particles on aggregation behavior.

Main Methods:

• Development of an analytical thermodynamic model based on self-assembly theory.
• Validation of the model using Langevin simulations of discoidal and depletant particles.
• Inclusion of attractive interactions between particle types to study their effect on aggregation.

Main Results:

• The thermodynamic model accurately describes depletion-induced aggregation of discoidal colloids.
• Langevin simulations confirm the model's predictions for emergent depletion interactions.
• An attractive interaction between depletant and discoidal particles leads to a re-entrant aggregation-temperature dependence.

Conclusions:

• Depletion interactions provide a fundamental mechanism for the self-assembly of discoidal colloids into columnar structures.
• The developed thermodynamic model and simulations offer a robust framework for studying such systems.
• Tunable aggregation behavior, including re-entrant phase transitions, can be achieved by modifying inter-particle attractions.