Dynamics of a membrane coupled to an active fluid

Area of Science:

• Soft Matter Physics
• Biophysics
• Active Matter Physics

Background:

• Membrane dynamics are crucial in biological systems.
• Active fluids, like actomyosin, exhibit complex behaviors.
• Understanding fluid-membrane interactions is key to cellular processes.

Purpose of the Study:

• To theoretically investigate the dynamics of a membrane coupled to an active fluid with rotational symmetry.
• To differentiate the behavior from systems involving polar active fluids.
• To explore conditions leading to membrane stabilization or instability.

Main Methods:

• Theoretical modeling of membrane-fluid coupling.
• Analysis of director field symmetry in the active fluid.
• Perturbation analysis to study stability and relaxation dynamics.

Main Results:

• Contractile active fluids can slow membrane relaxation for specific wavelengths only at high viscosity.
• A finite-wavelength instability is predicted for contractile fluids under strong contractility.
• Extensile active fluids consistently destabilize membranes against long-wavelength perturbations.

Conclusions:

• The rotational symmetry of the active fluid's director field leads to distinct membrane dynamics compared to polar active fluids.
• Membrane stability is highly dependent on fluid viscosity and contractility/extensibility.
• The findings are relevant for understanding in vitro actomyosin-membrane systems.