Motility-induced shear thickening in dense colloidal suspensions

Area of Science:

• Soft matter physics
• Non-equilibrium statistical mechanics
• Colloidal science

Background:

• Active colloidal suspensions are complex systems exhibiting rich collective dynamics.
• Understanding their rheological behavior under shear is crucial for applications.
• Out-of-equilibrium systems present unique challenges and opportunities in physics.

Purpose of the Study:

• Investigate the role of self-propulsion on the rheological response of dense colloidal suspensions.
• Analyze the combined effects of activity and shear on disordering transitions.
• Explore the steady-state rheological behavior of active sheared systems.

Main Methods:

• Particle-resolved Brownian dynamics simulations were employed.
• The study focused on dense colloidal suspensions.
• Analysis included disordering transitions and steady-state rheology.

Main Results:

• Self-propulsion significantly lowers the stress barrier for the disordering transition.
• Particle motility fluidizes passive suspensions.
• Active suspensions exhibit shear-thinning at low self-propulsion and shear-thickening at higher self-propulsion due to motility-induced clustering (MIST).

Conclusions:

• Self-propulsion fundamentally alters the phase transitions and rheology of colloidal suspensions.
• Motility-induced shear thickening (MIST) is a newly identified phenomenon in sheared active colloids.
• This finding offers a pathway to tailor the rheological properties of colloidal materials.