Non-Equilibrium Assembly of Light-Activated Colloidal Mixtures

Area of Science:

• Colloid and Surface Science
• Active Matter Physics
• Materials Science

Background:

• Artificial active matter systems offer unique pathways for creating non-equilibrium microscale structures.
• Understanding collective phenomena in active matter is key to designing novel materials and devices.

Purpose of the Study:

• To demonstrate the directed crystallization of passive silica colloids using a minimal number of active colloids.
• To investigate the control over assembly size, shape, and symmetry in dynamic colloidal crystals.

Main Methods:

• Utilizing titania-silica Janus particles as active colloids, propelled by UV light.
• Employing varying light intensities to modulate the attractive interactions and control cluster formation.
• Observing the directed self-assembly of passive silica colloids guided by active particles.

Main Results:

• A small population of active Janus particles effectively directed the assembly of passive silica colloids into 2D crystalline structures.
• The extent and characteristics of the assembled colloidal clusters were tunable via light intensity.
• The system successfully produced rationally designed colloidal clusters and crystals with controllable parameters.

Conclusions:

• This active matter system provides a method for fabricating dynamic colloidal crystals with precise control over structure.
• The approach allows for the creation of complex assemblies not achievable in equilibrium systems.
• This work opens possibilities for designing advanced microscale structures for various applications.