Microdynamics of active particles in defect-rich colloidal crystals

Area of Science:

• Colloidal science
• Soft matter physics
• Materials science

Background:

• Active colloidal particles exhibit unique self-propulsion, differing from passive Brownian motion.
• Understanding active particle interactions is crucial for controlling colloidal crystal formation and annealing.

Purpose of the Study:

• To investigate how active particles influence colloidal crystal annealing.
• To explore the role of microstructural regions on active particle dynamics within a crystal.

Main Methods:

• A quasi-2D colloidal crystal monolayer was created using AC electric fields.
• Platinum Janus spheres, propelled by hydrogen peroxide decomposition, were used as active particles.
• Mean-squared displacement was measured to analyze active particle dynamics in different microstructural regions (voids, void-adjacent, interstitial).

Main Results:

• Active particles increased average void size by up to three times and void anisotropy by 40%.
• Active particle concentration was higher in void and void-adjacent regions.
• Enhanced dynamics of active particles were most significant in void-adjacent regions.

Conclusions:

• Active particle microdynamics within crystal lattices are influenced by local defect structures.
• Active particles contribute to colloidal crystal annealing through their interactions with microstructural defects.