Yielding in dense active matter

Area of Science:

• Physics of granular materials
• Soft matter physics
• Rheology of active matter

Background:

• Dense active matter models animal collectives and reconfigurable materials.
• Understanding its mechanical response and constitutive laws is crucial but challenging.
• Existing models struggle to predict flow and failure under active forcing.

Purpose of the Study:

• Investigate the yielding transition in dense active matter under slow driving and high persistence.
• Compare the mechanical response of ultrastable materials under shear versus active forcing.
• Develop a predictive constitutive model for active granular matter.

Main Methods:

• Studied yielding transitions in dense active matter across various preparations.
• Applied shear and random active forcing to ultrastable materials.
• Developed and tested a modified elastoplastic model incorporating active driving field correlations.

Main Results:

• Ultrastable active matter is always ductile under random active forcing.
• A modified elastoplastic model accurately captures this ductile behavior.
• The correlation length of the active driving field is a key predictive parameter.
• Plastic flow is often predictable by active driving, independent of structural disorder.

Conclusions:

• Active forcing fundamentally alters the yielding behavior of ultrastable granular matter.
• The developed model provides a framework for understanding and predicting active matter rheology.
• Findings suggest new strategies for controlling granular active matter flow and solidification.