Chemotaxis in a binary mixture of active and passive particles

Area of Science:

• Colloid Science
• Soft Matter Physics
• Chemical Engineering

Background:

• Active colloids generate chemical gradients that influence passive particle motion.
• Diffusiophoresis drives passive colloids towards active ones via self-phoretic mechanisms.
• Understanding these interactions is key to controlling self-assembly.

Purpose of the Study:

• To investigate the self-assembly dynamics of active and passive colloid mixtures.
• To determine the state diagram based on diffusiophoretic attraction strength.
• To characterize the clustering behavior and dynamics.

Main Methods:

• Simulating Langevin dynamics of active and passive colloids.
• Varying the diffusiophoretic parameter to control attraction strength.
• Analyzing particle distribution and cluster formation over time.

Main Results:

• Three distinct self-assembly states were identified: scattering, oscillation between cloud and cluster, and single stable cluster formation.
• The diffusiophoretic parameter dictates the transition between these states.
• In the collapse regime, cluster dynamics follow logistic and power-law behaviors.

Conclusions:

• The diffusiophoretic strength is a critical parameter controlling active-passive colloid self-assembly.
• Simulations provide a framework for understanding experimental observations in similar systems.
• This work offers insights into designing and predicting self-assembling colloidal systems.