Active phase separation triggered by chemotactic defects

Area of Science:

• Physics
• Soft Matter Physics
• Biophysics

Background:

• Motility-Induced Phase Separation (MIPS) is a key phenomenon in active matter.
• Achieving MIPS at low particle densities (binodal region) is computationally challenging.
• Existing models often require high packing fractions or long simulation times.

Purpose of the Study:

• To investigate a novel mechanism for rapid MIPS in the dilute regime.
• To explore the role of defects in initiating and driving phase separation.
• To provide insights into biological aggregation processes, such as biofilm formation.

Main Methods:

• Numerical simulations of active suspensions.
• Analysis of defect dynamics and their influence on particle aggregation.
• Varying initial conditions and system parameters to study defect-triggered MIPS.

Main Results:

• Defects act as effective chemotactic centers, rapidly forming local particle aggregates.
• These aggregates can grow and coalesce, leading to full phase separation.
• The defect-triggered mechanism significantly reduces the time and computational cost for MIPS in the binodal region.

Conclusions:

• Defect-induced aggregation provides an efficient pathway for MIPS at low densities.
• This mechanism offers a potential explanation for bacterial aggregation into biofilms.
• Nutrient particles may serve as chemotactic attractors, similar to defects in physical models.