Nanovesicles drive a tunable dynamical arrest of microparticles

Area of Science:

• Colloidal science
• Soft matter physics
• Biophysics

Background:

• Vitrification in dilute colloidal systems typically requires asymmetric particle sizes and relies on entropy-driven depletion forces.
• Understanding dynamical arrest mechanisms is crucial for various scientific fields, including biological systems.

Purpose of the Study:

• To investigate a novel dynamical arrest mechanism in dilute asymmetric colloidal mixtures driven by energy rather than entropy.
• To explore the impact of vesicle phase transitions and electrostatic interactions on system dynamics and rheology.

Main Methods:

• Studied an extremely dilute asymmetric mixture of nanovesicles and polystyrene microparticles.
• Analyzed particle dynamics and mean square displacements during vesicle gel-fluid phase transitions.
• Investigated the effect of doping nanovesicles with charged lipids on system rheology.

Main Results:

• Identified an energy-driven dynamical arrest mechanism, distinct from entropy-driven depletion forces.
• Observed a sudden splitting in microparticle mean square displacements, indicating a viscous jump during vesicle phase transitions.
• Found that electrostatic repulsion, induced by charged lipids, leads to athermal, Newtonian rheology.

Conclusions:

• The study reveals a new pathway for dynamical arrest in colloidal systems, emphasizing the role of energy.
• Vesicle phase transitions significantly influence particle dynamics, leading to observable viscous jumps.
• Electrostatic interactions can fundamentally alter the rheological properties of such mixtures, offering insights into biological systems with complex charge distributions.