Hydrodynamically Interrupted Droplet Growth in Scalar Active Matter

Area of Science:

• Physics of active matter
• Soft matter physics
• Fluid dynamics

Background:

• Microphase separation is common in suspensions of active particles.
• Continuum models link particle density to fluid flow via effective interfacial tensions.
• Two tensions exist: mechanical (flow-inducing) and diffusive (Ostwald ripening).

Purpose of the Study:

• To investigate the role of negative mechanical tension in active particle suspensions.
• To elucidate the droplet life cycle driven by self-shearing instability.
• To analyze the impact of negative diffusive tension on droplet dynamics.

Main Methods:

• Continuum modeling of active particle suspensions.
• Analysis of self-shearing instability in contractile systems.
• Theoretical prediction of scaling behavior for droplet growth and division.

Main Results:

• Negative mechanical tension in contractile swimmers drives a droplet growth-and-division life cycle via self-shearing instability.
• The scaling behavior of this life cycle is theoretically predicted.
• Negative diffusive tension leads to an arrested regime, preventing small droplet division through reverse Ostwald ripening.

Conclusions:

• Negative mechanical tension is a key driver of dynamic microphase separation in active matter.
• The interplay between mechanical and diffusive tensions dictates droplet evolution pathways.
• This work provides a framework for understanding emergent behaviors in active suspensions.