Biological & Soft Matter Seminar: Heterogeneous fluid membranes in passive and active embedding media

Abstract:

Heterogeneous or mixed inversion-symmetric fluid membranes are routinely used in laboratories to experimentally study miscibility phase separation transitions (MPTs). It is now well-known that for membranes in equilibrium these MPTs are second order in nature belonging to the two-dimensional (2D) Ising universality class. We show that close to the critical point (CP) of the MPTs, for sufficiently strong curvature-composition interactions, mediated through a composition-dependent bending modulus, composition fluctuations lead to suppression of the membrane conformation fluctuations, compared to pure membranes. When the membrane is embedded in an active isotropic medium (e.g., actin filaments with motors in their isotropic phases), the active processes generically either stiffen or soften the fluid membranes. We argue that the membrane fluctuations carry definite signatures of the associated nonequilibrium MPTs. Our results may be tested by performing experiments on mixed lipid membranes embedded in a suspension of actin filaments with motors.

Seminar Organizer: Guy Yaacoby