Controlling liquid-liquid phase behaviour with an active fluid

Area of Science:

• Soft Matter Physics
• Active Matter Systems
• Biophysics

Background:

• Liquid-liquid phase separation is typically explained by equilibrium thermodynamics.
• Out-of-equilibrium phase transitions in binary fluid mixtures are challenging to predict and design.
• Active fluids introduce complexities beyond traditional thermodynamic models.

Purpose of the Study:

• To investigate the effect of activity on liquid-liquid phase separation in binary fluid mixtures.
• To explore the role of mechanical interactions between active components and phase-separating liquids.
• To understand the fundamental principles governing out-of-equilibrium phase transitions in active matter.

Main Methods:

• Utilized attractive DNA nanostars as a model system for liquid-liquid phase separation.
• Employed a microtubule-based active fluid to drive the system away from equilibrium.
• Conducted numerical simulations to validate experimental observations.

Main Results:

• Active fluid significantly lowers the critical temperature of demixing.
• Activity narrows the coexistence concentrations range.
• These effects are pronounced when mechanical bonds link active fluid and liquid droplets.

Conclusions:

• Activity suppresses the critical point in liquid-liquid phase separation, a potentially generic phenomenon in active matter.
• The findings provide a versatile platform for creating feedback-controlled soft active materials.
• This research offers insights into self-organization mechanisms relevant to cell biology.