Interaction between a macrosphere and a flat wall mediated by a hard-sphere colloidal suspension

Area of Science:

• Physics
• Physical Chemistry
• Colloid Science

Background:

• Understanding particle interactions in complex fluids is crucial for materials science.
• Binary fluids with large size asymmetry present unique interaction dynamics.
• Continuum approximations for smaller particles can oversimplify fluid behavior.

Purpose of the Study:

• To investigate the interaction between a macrosphere and a flat wall in a bidisperse hard-sphere fluid.
• To elucidate the role of the smaller particle component in modifying macrosphere-wall interactions.
• To quantify the effect on depletion attraction and particle adsorption.

Main Methods:

• Simulations of a macrosphere and flat wall in a binary fluid of hard spheres.
• Analysis of excluded-volume interactions and depletion forces.
• Comparison with single-component fluid interactions.

Main Results:

• Highly size-asymmetric particles qualitatively alter macrosphere-wall excluded-volume interactions.
• The smaller fluid component significantly modifies predicted macrosphere-wall depletion attraction.
• Depletion attraction is enhanced by small particles, promoting adsorption and structuring of large particles on the wall.

Conclusions:

• The primitive description of bidisperse fluids is insufficient; the fine component plays a critical role.
• Small particles are essential for accurately modeling depletion attraction in such systems.
• This work provides insights into colloidal assembly and interfacial phenomena in complex fluids.