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The behavior of active diffusiophoretic suspensions: An accelerated Laplacian dynamics study.
1Department of Mechanical and Civil Engineering, California Institute of Technology, Pasadena, California 91125, USA.
The Journal of Chemical Physics
|October 27, 2016
Summary
Chemically active particles create concentration gradients, driving their motion and that of others. Simulations reveal "chemical screening" stabilizes diffusiophoretic suspensions, showing self-propulsion doesn't affect clustering thresholds.
Area of Science:
- Colloid science
- Active matter physics
- Chemical physics
Background:
- Diffusiophoresis describes particle movement due to solute concentration gradients.
- Chemically active particles generate these gradients via reactions, causing self-motion (Janus particles) or moving neighbors.
- Long-range interactions in reactive particle systems can lead to complex behaviors like clustering.
Purpose of the Study:
- To develop a general simulation method for many-particle diffusiophoresis.
- To investigate the role of solute concentration fields in the dynamics of reactive particles.
- To clarify the phenomenon of chemical screening and its impact on system stability.
Main Methods:
- Developed a general method to determine the many-particle solute concentration field.
- Performed dynamic simulations of thousands of reactive particles.
- Analyzed particle clustering and coexistence phenomena under varying conditions.
Main Results:
- Demonstrated "chemical screening," which exponentially screens long-range interactions and stabilizes diffusiophoretic suspensions.
- Uniformly reactive particles form loose clusters, but no phase coexistence is observed.
- Identified a stability threshold where Brownian motion overcomes diffusiophoretic attraction at low fuel concentrations.
- Self-propelling Janus particles exhibit coexistence, yet their clustering stability threshold is unaffected by self-motion.
Conclusions:
- The developed simulation method accurately captures complex behaviors in diffusiophoretic systems.
- Chemical screening is crucial for the stability of diffusiophoretic suspensions.
- Self-motion of Janus particles does not alter the fundamental stability threshold for clustering, which is governed by fuel concentration.
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