Geometric control of motility-induced phase separation

Area of Science:

• Physics
• Soft Matter Physics
• Active Matter Physics

Background:

• Curvature significantly impacts soft, active, and biological materials.
• Motility-induced phase separation (MIPS) is a key non-equilibrium transition in active matter.

Purpose of the Study:

• To investigate how geometric curvature influences MIPS.
• To explore the use of curved spaces for understanding active matter dynamics.

Main Methods:

• Studied active Brownian particles on a torus surface.
• Varied the torus aspect ratio to induce geometric changes.
• Analyzed the morphology and location of MIPS clusters.

Main Results:

• Weak curvature robustly controls MIPS cluster location and morphology.
• Torus aspect ratio changes drive MIPS cluster transitions from disk to band structures.
• Cluster boundary geometries favor a thermodynamic over a simple kinetic MIPS model.

Conclusions:

• Curved geometry offers precise control over active matter self-organization.
• Curved spaces serve as sensitive platforms for probing fundamental MIPS mechanisms.
• Results support a boundary-length-minimizing picture for MIPS in the large-particle limit.