Dynamic Interactions between a Silica Sphere and Deformable Interfaces in Organic Solvents Studied by Atomic Force...

Area of Science:

• Colloid and Surface Science
• Materials Science
• Rheology

Background:

• Atomic Force Microscopy (AFM) and Stokes-Reynolds-Young-Laplace (SRYL) equations model surface forces and deformations.
• Natural polyaromatic molecules (NPAMs) create viscoelastic, elastic-dominant oil-water interfaces upon aging.
• Conventional SRYL equations are limited to purely Laplacian interfaces.

Purpose of the Study:

• Investigate interactions between silica particles and viscoelastic water droplets in crude oil.
• Analyze the impact of NPAM-induced interfacial aging on droplet deformation.
• Develop an improved model for non-Laplacian interfaces with viscoelasticity.

Main Methods:

• Utilized AFM to measure forces between silica spheres and deformable water droplets.
• Employed SRYL equations to model interfacial deformation.
• Measured interfacial tension, dilatational rheology, and interfacial "crumpling" to characterize the mechanical barrier.
• Introduced a viscoelasticity parameter to refine deformation predictions.

Main Results:

• SRYL equations inadequately modeled droplet deformation due to interfacial viscoelasticity and non-Laplacian effects.
• Droplet deformation was overpredicted by SRYL after initial aging periods.
• A viscoelasticity parameter successfully corrected discrepancies, enabling accurate prediction of AFM-induced droplet deformation.
• Interfacial aging led to increased elasticity and formation of a rigid interfacial network.

Conclusions:

• Conventional SRYL models fail for viscoelastic, non-Laplacian interfaces.
• A novel viscoelasticity parameter is essential for accurate modeling of such systems.
• Findings are relevant for understanding complex interfaces in biological and material systems.