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Updated: May 15, 2025
11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
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Active phase separation: new phenomenology from non-equilibrium physics.
1DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
Summary
Active systems exhibit unique fluid-fluid phase separation due to non-equilibrium dynamics. This review explores how broken detailed balance and novel interfacial tensions drive these phenomena, differing from equilibrium systems.
Area of Science:
- Soft Matter Physics
- Non-equilibrium Statistical Mechanics
- Active Matter Theory
Background:
- Fluid-fluid phase separation is common in active systems with local non-equilibrium dynamics, seen in biological and synthetic systems.
- Traditional understanding of phase separation from equilibrium systems assumes detailed balance, which is absent in active systems.
- The absence of detailed balance fundamentally alters phase separation mechanisms, leading to phenomena not observed in equilibrium.
Purpose of the Study:
- To review recent advancements in understanding the role of activity in fluid-fluid phase separation.
- To highlight novel phenomena driven by non-equilibrium dynamics, such as reverse Ostwald ripening.
- To discuss the theoretical frameworks and experimental comparisons for active phase separation.
Main Methods:
- Focus on continuum field theories, particularly those with a single conserved scalar order parameter and supplemented velocity fields.
- Review analytical and numerical studies of these continuum theories.
- Compare theoretical predictions with particle-based models and experimental observations.
Main Results:
- Active phase separation can exhibit distinct interfacial tensions, including negative values, leading to unique phenomena like reverse Ostwald ripening.
- The phenomenology of phase separation is radically altered by the absence of detailed balance in active systems.
- Continuum theories provide a framework to understand these complex behaviors, with qualitative agreement from particle models and experiments.
Conclusions:
- Activity introduces novel mechanisms and phenomena in fluid-fluid phase separation beyond equilibrium predictions.
- Continuum theories are powerful tools for studying active matter, though experimental validation faces challenges due to system complexity.
- Further research is needed to fully elucidate the diverse regimes and open questions in active phase separation.
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