Dynamics of rigid and flexible extended bodies in viscous films and membranes

TL;DR

This paper investigates the movement and internal dynamics of extended bodies in viscous membranes and films, revealing distinct mobility behaviors and dynamical regimes for semiflexible inclusions.

Contribution

It introduces new insights into the mobility differences between membrane and bulk fluid environments and characterizes internal mode dynamics of semiflexible bodies.

Findings

Large inclusions exhibit purely local drag with algebraic dependence on size.

Distinct dynamical regimes are identified in the relaxation spectrum of semiflexible inclusions.

Mobility in membranes differs significantly from bulk fluids, especially for large bodies.

Abstract

We study the dynamics of extended rod-like bodies in (or associated with) membranes and films. We demonstrate a striking difference between the mobilities in films and bulk fluids, even when the dissipation is dominated by the fluid stress: for large inclusions we find that rotation and motion perpendicular to the rod axis exhibits purely local drag, in which the drag coefficient is algebraic in the rod dimensions. We also study the dynamics of the {\em internal} modes of a semiflexible inclusion and find two dynamical regimes in the relaxation spectrum.