Slip and flow in soft particle pastes

Area of Science:

• Rheology
• Soft Matter Physics
• Colloid Science

Background:

• Concentrated dispersions of soft particles are common in various applications, including food, cosmetics, and pharmaceuticals.
• Understanding their flow behavior near surfaces is crucial for process design and product performance.
• Previous studies have explored slip phenomena, but a unified explanation for soft particles has been lacking.

Purpose of the Study:

• To investigate the fundamental mechanism of slip in concentrated soft particle dispersions near smooth surfaces.
• To develop a predictive model for slip behavior based on particle-wall interactions.
• To gain insights into the relationship between slip and the bulk properties of the paste.

Main Methods:

• Theoretical modeling based on the balance of forces acting on soft particles near a wall.
• Analysis of osmotic forces arising from particle concentration gradients.
• Consideration of noncontact elastohydrodynamic interactions between deformed particles and the surface.

Main Results:

• Soft particle dispersions exhibit a generic slip behavior, independent of specific particle composition.
• Slip is governed by a balance between repulsive osmotic forces and attractive elastohydrodynamic forces.
• The proposed model accurately predicts slip length and shear thinning behavior.

Conclusions:

• Slip in concentrated soft particle dispersions is a universal phenomenon driven by fundamental interactions.
• The developed model provides a valuable tool for predicting and controlling the flow of pastes and similar materials.
• This work advances the understanding of interfacial phenomena in soft matter systems.