Active liquid-liquid phase separation in a confining environment.

Area of Science:

• Cell biology
• Biophysics
• Statistical mechanics

Background:

• Liquid-liquid phase separation (LLPS) is crucial in cellular processes.
• LLPS in confined environments may consume free energy, potentially violating the Principle of Detailed Balance (PDB).
• Previous models showed PDB is maintained macroscopically if only droplet radius is considered a collective coordinate.

Purpose of the Study:

• To investigate active LLPS in a confining environment with droplet location as a second collective coordinate.
• To analyze the macroscopic implications of active noise on the Principle of Detailed Balance.
• To explore the role of confining potentials in active phase separation dynamics.

Main Methods:

• Development of a simple model for active LLPS within a confining potential.
• Inclusion of droplet location as a second collective coordinate alongside droplet radius.
• Application of the Fluctuation-Dissipation Theorem as a diagnostic tool.

Main Results:

• Active LLPS in this model breaks the Principle of Detailed Balance at the macroscopic level.
• Active noise asymmetrically suppresses linear susceptibility.
• Active noise also suppresses the quasicritical thermal noise spectrum in an unusual manner.

Conclusions:

• Macroscopic violation of PDB is possible in active LLPS under confinement when multiple collective coordinates are considered.
• Active noise introduces novel, asymmetric dynamics to phase separation processes.
• This work provides new insights into the thermodynamics and statistical mechanics of active biological systems.