Dynamics of filaments and membranes in a viscous fluid

Motivated by the motion of biopolymers and membranes in solution, this article presents a formulation of the equations of motion for curves and surfaces in a viscous fluid. The focus is on geometrical aspects and simple variational methods for calculating internal stresses and forces, and the full nonlinear equations of motion are derived. In the case of membranes, particular attention is paid to the formulation of the equations of hydrodynamics on a curved, deforming surface. The formalism is illustrated by two simple case studies: (1) the twirling instability of straight elastic rod rotating in a viscous fluid and (2) the pearling and buckling instabilities of a tubular liposome or polymersome.