Memory of shear flow in soft jammed materials.

Area of Science:

• Rheology
• Soft Matter Physics
• Computational Materials Science

Background:

• Yield stress fluids exhibit a memory effect where prior flow conditions influence subsequent stress relaxation.
• Understanding the microscopic origins of this memory is crucial for predicting fluid behavior.

Purpose of the Study:

• To investigate the microscopic mechanisms behind the memory effect in yield stress fluids.
• To link flow conditions to stress relaxation dynamics and residual stress magnitudes.

Main Methods:

• Combined experimental techniques with large-scale computer simulations.
• Studied jammed suspensions of soft repulsive particles.
• Performed spatiotemporal analysis of particle motion.

Main Results:

• Flow induces spatially correlated nonaffine displacements, forming domains that store stress imbalance information.
• Particle packing reorganizes to minimize flow resistance, contributing to stress relaxation.
• A correlation exists between particle displacement patterns during flow and upon cessation.

Conclusions:

• Flow acts as a 'training' process, encoding information in particle displacements and packing.
• This encoded memory governs the stress relaxation and residual stress in yield stress fluids.
• The study reveals the microscopic basis for memory phenomena in these complex fluids.