Shear-affected depletion interaction

Area of Science:

• Colloid and interface science
• Soft matter physics
• Rheology

Background:

• Depletion interactions are crucial in colloidal systems.
• Flow fields can alter particle interactions.
• Understanding non-equilibrium effects is vital for complex fluids.

Purpose of the Study:

• To investigate how shear flow influences depletion interactions caused by disc-shaped depletants.
• To explore the concentration-dependent effects of flow on depletion potentials.
• To adapt Total Internal Reflection Microscopy (TIRM) for non-equilibrium measurements.

Main Methods:

• Modification of the Total Internal Reflection Microscopy (TIRM) technique.
• Application of controlled shear rates to colloidal dispersions.
• Measurement of particle-wall interaction potentials under flow.

Main Results:

• At low depletant concentrations, increasing shear rate reduces depletion potential depth.
• Depletion force becomes experimentally undetectable at high shear rates for low concentrations.
• Above a critical depletant concentration, flow effects on depletion potential become negligible.

Conclusions:

• Flow alignment of disc-shaped depletants likely explains reduced depletion at low concentrations.
• The vanishing influence of flow at high depletant concentrations requires further investigation.
• Modified TIRM is suitable for studying particle interactions under shear flow conditions.